The effect of ANK3 bipolar-risk polymorphisms on the working memory circuitry differs between loci and according to risk-status for bipolar disorder

Polymorphisms at the rs10994336 and rs9804190 loci of the Ankyrin 3 (ANK3) gene have been strongly associated with increased risk for bipolar disorder (BD). However, their potential pathogenetic effect on BD-relevant neural circuits remains unknown. We examined the effect of BD-risk polymorphisms at rs10994336 and rs9804190 on the working memory (WM) circuit using functional magnetic resonance imaging (fMRI) data obtained from euthymic patients with BD (n = 41), their psychiatrically healthy first-degree relatives (n = 25) and unrelated individuals without personal or family history of psychiatric disorders (n = 46) while performing the N-back task. In unrelated healthy individuals, the rs10994336-risk-allele was associated with reduced activation of the ventral visual cortical components of the WM circuit while the rs9804190-risk-allele was associated with inefficient hyperactivation of the prefrontal cortical components of the WM. In patients and their healthy relatives, risk alleles at either loci were associated with hyperactivation in the ventral anterior cingulate cortex. Additionally, Rs9804190-risk-allele carriers with BD evidenced abnormal hyperactivation within the posterior cingulate cortex. This study provides new insights on the neurogenetic correlates of allelic variation at different genome-wide supported BD-risk associated ANK3 loci that support their involvement in BD and highlight the modulatory influence of increased background genetic risk for BD

Towards an evolutionary perspective of bipolar disorders: Is there a genetic link between bipolar disorders and non-pathological (adaptive) hyperactivity?

The new-developed Questionnaire for Adaptive Hyperactivity and Goal Achievement (AHGA), represents an innovative approach to hyperthymic features by embracing a broader concept of spectrum, which conceptualizes as a continuum the potential transition between pathological and adaptive aspects. The two basic components of the hyperthymic temperament that stand out are hyperactivity and goal achievement. This kind of temperament can be classified as abnormal only in the presence of chronic hypomanic symptoms or advanced mood disorders. In general, temperaments have been verified to belong to the domain of normality rather than the sphere of pathology, in accordance with their putative adaptive role. Commonly, achieving success, experiencing excitement and joy, and moving towards core life goals are moments of great importance in life. In this approach, goal and drive achievement demonstrates an adaptive and beneficial side of hyperthymia. It indicates the willingness to set high goals and spend energy pursuing them, which could help clarify the high rates of creative efforts among people with a hyperthymic temperament. However, the pathological scenery appears linked to variability in the adaptiveness with which people follow life goals and accomplishments. In the later stages of the study, this tool was very helpful in identifying older adults (60 years of age and older) with features of well-defined hyperactivity and novelty-seeking. The Questionnaire for Adaptive Hyperactivity and Goal Achievement (AHGA) measures the adaptive characteristics of hyperactivity and goal pursuit in contrast to the Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN) tool, which measures its pathological characteristics. According to the results regarding the investigated genetic variant (RS1006737) of the CACNA1C gene, an association was found with the characteristics of hyperactivity rather than just BD. Also, this genetic variant, recognized in the literature as associated with bipolar disorders, was found in well-adapted older adults without bipolar disorders and high hyperactivity traits with a similar frequency as in older adults with a diagnosis of bipolar disorders but higher than in older adults without bipolar disorders and without hyperactivity. This could led to the new interpretation and a new approach to supporting drug therapy in which the rediscovery of the adaptive potential resources would be central to the recovery of the individual who has suffered a bipolar disorder onset. Furthermore, the interpretation of the disorder not as the simple consequence of a genetic weakness could be an element against stigma and self-stigma. When comparing the biological material, although saliva and blood differ in composition and biological properties, sample type has no effect on the detection of a mutation in the genetic variant of interest. Blood and saliva can both be used as biological materials in later stages of this research. The combination of the new questionnaire tool (Questionnaire for Adaptive Hyperactivity and Goal Achievement) with the genetic analysis appears to be an innovative, practicable, and original approach. The following development of this study will include more genetic variables with higher susceptibility for bipolar disorders (ANK3, NCAN, ODZ4, SYNE1, and TRANK1 genes) and obviously more numerous target and control samples

Characterisation of genetic risk factors for mental illness in rodent models, impact of Map2k7+/- and Fxyd6-/- mice on neural systems and working memory

Even in wealthy and seemingly prosperous countries like the United Kingdom, the spectre of mental illness and psychiatric disorders remains highly prevalent. These disorders present a huge economic burden to societies, where in the UK alone, mental disorders cost the economy an estimated €134 billion a year; along with the unmeasurable societal and human costs. This has led to an intense debate over the past few decades just as to what factors contribute to these illnesses. It is now understood that a number of biological and non-biological factors contribute. These include socio-economic pressures, early-life trauma, gestational and peri-natal infections; genetic and familial factors, and molecular and cellular factors. However, while the definitions and diagnostic criteria of mental disorders remain based in the subjective realms of the DSM and ICD, treatment and understanding of psychiatric illness has had little chance to progress over the last fifty years. As a result, neuroscientists are starting to direct psychiatric disorder research from the bottom-up; where genetic, cognitive and neuroconnectivity factors are being investigated to serve as a future basis for diagnosis and treatment. One of the most complex and debilitating psychiatric disorders, schizophrenia, exhibits a complex array of genetic, cognitive and neuroconnectivity abnormalities. Current challenges in schizophrenia research is to understand how identified genetic abnormalities contribute to neuroconnectivity and cognitive impairments which are prominent in schizophrenia. Recently, genetic association studies have implicated two genes as risk factors for schizophrenia - FXYD6 and MAP2K7. Currently it is unclear exactly how these genes contribute to schizophrenia pathology, particularly cognitive symptoms and neural circuitry.;This thesis investigates these two genes by utilising two mouse models, first a heterozygous mouse line of Map2k7+/- and second, a gene knock-out line of Fxyd6-/-. MAP2K7 is a gene that expresses a kinase that is involved in the c-Jun N-terminal kinase (JNK) pathway, which is implicated in neuronal activity, receptor function, and cortical and hippocampal plasticity. Recent studies have found a decreased expression of MA2PK7 in the PFC, ACC and hippocampal regions in schizophrenia patients; regions associated with memory and decision making. A component of the cognitive profile of MAP2K7 was therefore investigated using Map2k7+/- mouse lines in a working memory paradigm in the radial arm maze. This test is known as the n-back test or the retention interval test. For the first time this investigation reveals that Map2k7+/- mice exhibit a subtle yet significant spatial working memory deficit compared to WT mice; as judged by their average performance over the whole experiment. WT mice exhibited an overall average performance of 70% and MAP2K7+/- mice 66% (p<0.001). This indicates that MAP2K7 may play a subtle role in working memory function in rodents, and may represent a component of the aberrations in the genetic architecture that gives rise to working memory impairments in psychiatric disorders, particularly schizophrenia. This experiment also backs up previous evidence for this radial arm maze paradigm as a robust behavioural test for testing rodent working memory.;FXYD6 belongs to a group of proteins that are known to be involved in modulating NaKATPase activity. Previously, NaKATPase has been associated with bipolar disorder and depression, but has now also been implicated in schizophrenia. Previous studies have found that FXYD6 is also abnormally expressed in the PFC of schizophrenia patients, and therefore may contribute to the cognate symptoms of the disorder. This experiment, therefore, investigated how Fxyd6 contributes to local brain activation, particularly in neural systems relevant to cognition, using gene knockout Fxyd6-/- mouse models and semi quantitative 2DG autoradiographic imaging. Three regions showed a significant deviation in activity in Fxyd6-/- mice compared to WT mice. The subiculum, medial septum and lateral septum all exhibited significant reductions in activity in Fxyd6-/- mice compared to WT mice. Notably the subiculum is heavily implicated with memory functions, particularly working memory and disambiguation of previously learned memory. Indicating a possible role for FXYD6 and NaKATPase in working memory processing and memory disambiguation in the subiculum. Finally, the role of glutamate in relation to FXYD6 function and brain activity was assessed by administering the NMDA receptor antagonist ketamine and analysing regional brain activity using semi quantitative 2DG autoradiographic imaging. Generally, regions which were affected by ketamine in WT mice including PFC, thalamic and septal regions, were not affected in Fxyd6-/- mice. It is hypothesized that this may be down to a compensatory effect that knocking-out Fxyd6 may have on glutamate reuptake. Because NaKATPase is involved in glutamate reuptake into glia and neurons, the blockage of NMDA receptors may have less effect due to a reduction in glutamate reuptake, and therefore higher than normal postsynaptic glutamate concentrations. In conclusion, this investigation highlights two genes which may have roles in working memory functioning and neural circuitry that contribute to cognitive processes. While the evidence from this investigation does not explicitly associate these genes with symptoms of schizophrenia and other psychiatric disorders; the evidence does provide indication that they are involved in cognitive processes in rodents, and possibly humans. This investigation provides an interesting path of investigation for the potential roles of these genes regardless of their relationship to psychiatric disorders and will inform future research into the genetic architecture of neural circuits and cognition.Even in wealthy and seemingly prosperous countries like the United Kingdom, the spectre of mental illness and psychiatric disorders remains highly prevalent. These disorders present a huge economic burden to societies, where in the UK alone, mental disorders cost the economy an estimated €134 billion a year; along with the unmeasurable societal and human costs. This has led to an intense debate over the past few decades just as to what factors contribute to these illnesses. It is now understood that a number of biological and non-biological factors contribute. These include socio-economic pressures, early-life trauma, gestational and peri-natal infections; genetic and familial factors, and molecular and cellular factors. However, while the definitions and diagnostic criteria of mental disorders remain based in the subjective realms of the DSM and ICD, treatment and understanding of psychiatric illness has had little chance to progress over the last fifty years. As a result, neuroscientists are starting to direct psychiatric disorder research from the bottom-up; where genetic, cognitive and neuroconnectivity factors are being investigated to serve as a future basis for diagnosis and treatment. One of the most complex and debilitating psychiatric disorders, schizophrenia, exhibits a complex array of genetic, cognitive and neuroconnectivity abnormalities. Current challenges in schizophrenia research is to understand how identified genetic abnormalities contribute to neuroconnectivity and cognitive impairments which are prominent in schizophrenia. Recently, genetic association studies have implicated two genes as risk factors for schizophrenia - FXYD6 and MAP2K7. Currently it is unclear exactly how these genes contribute to schizophrenia pathology, particularly cognitive symptoms and neural circuitry.;This thesis investigates these two genes by utilising two mouse models, first a heterozygous mouse line of Map2k7+/- and second, a gene knock-out line of Fxyd6-/-. MAP2K7 is a gene that expresses a kinase that is involved in the c-Jun N-terminal kinase (JNK) pathway, which is implicated in neuronal activity, receptor function, and cortical and hippocampal plasticity. Recent studies have found a decreased expression of MA2PK7 in the PFC, ACC and hippocampal regions in schizophrenia patients; regions associated with memory and decision making. A component of the cognitive profile of MAP2K7 was therefore investigated using Map2k7+/- mouse lines in a working memory paradigm in the radial arm maze. This test is known as the n-back test or the retention interval test. For the first time this investigation reveals that Map2k7+/- mice exhibit a subtle yet significant spatial working memory deficit compared to WT mice; as judged by their average performance over the whole experiment. WT mice exhibited an overall average performance of 70% and MAP2K7+/- mice 66% (p<0.001). This indicates that MAP2K7 may play a subtle role in working memory function in rodents, and may represent a component of the aberrations in the genetic architecture that gives rise to working memory impairments in psychiatric disorders, particularly schizophrenia. This experiment also backs up previous evidence for this radial arm maze paradigm as a robust behavioural test for testing rodent working memory.;FXYD6 belongs to a group of proteins that are known to be involved in modulating NaKATPase activity. Previously, NaKATPase has been associated with bipolar disorder and depression, but has now also been implicated in schizophrenia. Previous studies have found that FXYD6 is also abnormally expressed in the PFC of schizophrenia patients, and therefore may contribute to the cognate symptoms of the disorder. This experiment, therefore, investigated how Fxyd6 contributes to local brain activation, particularly in neural systems relevant to cognition, using gene knockout Fxyd6-/- mouse models and semi quantitative 2DG autoradiographic imaging. Three regions showed a significant deviation in activity in Fxyd6-/- mice compared to WT mice. The subiculum, medial septum and lateral septum all exhibited significant reductions in activity in Fxyd6-/- mice compared to WT mice. Notably the subiculum is heavily implicated with memory functions, particularly working memory and disambiguation of previously learned memory. Indicating a possible role for FXYD6 and NaKATPase in working memory processing and memory disambiguation in the subiculum. Finally, the role of glutamate in relation to FXYD6 function and brain activity was assessed by administering the NMDA receptor antagonist ketamine and analysing regional brain activity using semi quantitative 2DG autoradiographic imaging. Generally, regions which were affected by ketamine in WT mice including PFC, thalamic and septal regions, were not affected in Fxyd6-/- mice. It is hypothesized that this may be down to a compensatory effect that knocking-out Fxyd6 may have on glutamate reuptake. Because NaKATPase is involved in glutamate reuptake into glia and neurons, the blockage of NMDA receptors may have less effect due to a reduction in glutamate reuptake, and therefore higher than normal postsynaptic glutamate concentrations. In conclusion, this investigation highlights two genes which may have roles in working memory functioning and neural circuitry that contribute to cognitive processes. While the evidence from this investigation does not explicitly associate these genes with symptoms of schizophrenia and other psychiatric disorders; the evidence does provide indication that they are involved in cognitive processes in rodents, and possibly humans. This investigation provides an interesting path of investigation for the potential roles of these genes regardless of their relationship to psychiatric disorders and will inform future research into the genetic architecture of neural circuits and cognition

Mutation of Semaphorin-6A Disrupts Limbic and Cortical Connectivity and Models Neurodevelopmental Psychopathology

Psychiatric disorders such as schizophrenia and autism are characterised by cellular disorganisation and dysconnectivity across the brain and can be caused by mutations in genes that control neurodevelopmental processes. To examine how neurodevelopmental defects can affect brain function and behaviour, we have comprehensively investigated the consequences of mutation of one such gene, Semaphorin-6A, on cellular organisation, axonal projection patterns, behaviour and physiology in mice. These analyses reveal a spectrum of widespread but subtle anatomical defects in Sema6A mutants, notably in limbic and cortical cellular organisation, lamination and connectivity. These mutants display concomitant alterations in the electroencephalogram and hyper-exploratory behaviour, which are characteristic of models of psychosis and reversible by the antipsychotic clozapine. They also show altered social interaction and deficits in object recognition and working memory. Mice with mutations in Sema6A or the interacting genes may thus represent a highly informative model for how neurodevelopmental defects can lead to anatomical dysconnectivity, resulting, either directly or through reactive mechanisms, in dysfunction at the level of neuronal networks with associated behavioural phenotypes of relevance to psychiatric disorders. The biological data presented here also make these genes plausible candidates to explain human linkage findings for schizophrenia and autism

Analysis of the impact of synaptic plasticity genes and Human Accelerated Regions on brain function and structure: from the healthy brain to schizophrenia

Programa de Doctorat en Biodiversitat / Tesi realitzada a FIDMAG Germanes Hospitalàries Research Foundation[eng] Schizophrenia is a severe psychiatric disorder affecting around 24 million people worldwide. While we begin to disentangle the biological actors implicated in the origin of the disorder, the precise aetiological mechanisms remain largely unknown. Therefore, psychiatry research efforts still need to focus on a better understanding of the complex biological foundations of the disorder to achieve more precise diagnoses and the development of novel therapeutic strategies improving the patients’ quality of life. The prevailing etiopathological hypothesis considers that schizophrenia originates from the interplay between subtle genetic and environmental insults that disrupt the perfectly orchestrated mechanisms guiding neurodevelopment. Additionally, from an evolutionary perspective, it is suggested that schizophrenia represents a costly trade-off in the evolution of human-specific ontogenic neurodevelopmental processes sustaining the inherent complexity and variability of brain functioning, cognition, and behaviour. Along the neurodevelopmental process, the synapse formation and the organisation and maturation of neural circuits anchor the emergence of distinctive human cortical brain functions. In turn, multidisciplinary evidence indicates that synaptic alterations participate in brain dysfunctions, eventually leading to the emergence of the symptoms and cognitive deficits of schizophrenia. Accordingly, it is suggested that synaptic plasticity impairments play a critical role in the pathophysiology of the disorder. Among genes converging in neurodevelopmental and synaptic plasticity pathways, there are genes mediating signalling pathways involved in neural homeostasis, dendritic spine development and neural excitability, such as KCNH2, DISC1, CACNA1C and ZNF804A, all of them previously associated with the risk for schizophrenia. Moreover, evolutionary approaches have identified regions that accumulated human-specific changes since the divergence from chimpanzees, like Human Accelerated Regions (HARs). These regions act as transcriptional regulatory elements that endow human neurodevelopment with unique characteristics and harbour schizophrenia genetic susceptibility variants. To facilitate the identification of the genetic and biological mechanisms involved in schizophrenia aetiology, the use of brain-based intermediate phenotypes is a valuable strategy. Following two approaches centred on the genetic-phenotypic correlates of synaptic plasticity candidate genes and HARs sequences in the brain-based alterations in schizophrenia, this thesis includes four original articles and one systematic review. In these articles, we report the effect of common polymorphisms in KCNH2, DISC1, CACNA1C and ZNF804A genes and the polygenic load of HARs-informative sets on the differences observed between healthy brains and brains with schizophrenia. Overall, the results validate the efficacy of neuroimaging phenotypes to identify the genetic determinants of schizophrenia and point out the complementarity of candidate genes and genome-wide approaches in the study of the genetic architecture of the disorder. First, we describe the role of KCNH2 and DISC1 genetic variability in modulating the attentional and working memory-related functional responses in a diagnosis- dependent manner. Furthermore, we identify that the epistasis between two schizophrenia GWAS-associated genes, CACNAC1C and ZNF804A, influence the functional ability to adapt to increased working memory difficulty euqally in healthy controls and patients with schizophrenia. Second, we present a review of how HARs underlie human neurodevelopmental signatures, brain configuration, functioning and susceptibility behind psychiatric disorders. Likewise, we report the modulatory effect of HARs polygenicity on brain cortical architectural differences in schizophrenia and provide evidence on the importance of foetal-active regulatory HARs in patients' cortical surface area variability. Globally, the findings exposed in this thesis point towards the fact that the aetiological foundations of schizophrenia are related to the individual genetic differences altering neurodevelopment and synaptic plasticity trajectories but also to the genomic make-up that defines us as a species. This thesis provides a drop in the ocean of knowledge on disorders inherently linked to the human condition and has sought to comprehend the unique characteristics of our brain to help unravel what it means to be human.[cat] L’esquizofrènia és un trastorn neuropsiquiàtric greu que afecta a 24 milions de persones a tot el món. Tot i que comencem a conèixer els mecanismes biològics implicats en l’origen del trastorn, els processos etiològics precisos continuen essent en gran part desconeguts. Per tant, els esforços en la recerca encara necessiten dirigir-se en millorar el coneixement dels fonaments biològics del trastorn, per tal d’aconseguir un diagnòstic més precís i el desenvolupament de noves estratègies terapèutiques que millorin la qualitat de vida dels pacients. La hipòtesi etiopatogènica predominant considera que el trastorn s’origina a partir de la interacció entre factors genètics i ambientals que pertorben els mecanismes perfectament orquestrats que guien el neurodesenvolupament. A més, des d’una perspectiva evolutiva, s’ha suggerit que l’esquizofrènia representaria el “preu a pagar” per evolució dels processos ontogènics específicament humans que sustenten la complexitat i la variabilitat inherent al funcionament del cervell, la cognició i el comportament de la nostra espècie. Al llarg del neurodevenvolupament, la formació de sinapsis i l’organització i maduració dels circuits neurals ancoren l’aparició de funcions cerebrals corticals distintivament humanes. Al seu torn, evidències multidisciplinàries indiquen que les alteracions sinàptiques participen en disfuncions cerebrals que tenen com a resultat l’aparició dels símptomes cognitius i clínics de l’esquizofrènia. En conseqüència, s’ha proposat que les alteracions de la plasticitat sinàptica tenen un paper crític en la fisiopatologia del trastorn. Entre els gens que conflueixen en vies del neurodesenvolupament i de plasticitat sinàptica, hi ha gens que participen en vies de senyalització implicades en l’homeòstasi neuronal, el desenvolupament de les espines dendrítiques i l’excitabilitat neuronal, com els gens KCNH2, el DISC1, el CACNA1C i el ZNF804A, tots prèviament associats amb el risc per a l’esquizofrènia. A més, aproximacions evolutives han identificat regions que han acumulat canvis específicament en humans des de la divergència amb els ximpanzés, com les Regions Humanes Accelerades (o Human Accelerated Regions, HARs en anglès). Aquestes regions actuen com a elements reguladors de la transcripció atorgant característiques úniques al neurodesenvolupament humà, i contenen variants genètiques de susceptibilitat per a l’esquizofrènia. Per tal de facilitar l’identificar els mecanismes genètics i biològics implicats en l’etiologia de l’esquizofrènia, la utilització de fenotips cerebrals intermedis, com mesures de neuroimatge funcional i estructural, representa una estratègia molt útil. Seguint dues aproximacions centrades en l’anàlisi dels correlats genètics-fenotípics entre gens candidats relacionats amb la plasticitat sinàptica i regions HARs i les alteracions cerebrals de l’esquizofrènia, aquesta tesi inclou quatre articles originals i una revisió sistemàtica. En aquests articles, exposem l’efecte de polimorfismes en els gens KCNH2, DISC1, CACNA1C i ZNF804A i la càrrega poligènica en conjunts informatius de HARs sobre les diferències observades entre cervells de persones sanes i persones amb esquizofrènia. En conjunt, els resultats validen l’efectivitat dels fenotips de neuroimatge per identificar els determinants genètics de l’esquizofrènia i posen de manifest la complementarietat de les aproximacions centrades tant en gens candidats com en la variabilitat global del genoma per a l’estudi de l’arquitectura genètica del trastorn. Primer, descrivim el paper de la variabilitat genètica dels genes KCNH2 i DISC1 en la modulació de la resposta funcional a l’atenció i la memòria de treball de manera condicionada al diagnòstic. També, identifiquem que l’epistasi entre dos gens associats amb l’esquizofrènia a nivell de GWAS, el CACNAC1C i el ZNF804A, influeix en la capacitat funcionalde cervell per adaptar-se a l’increment de requeriments cognitius en memòria de treball en controls sans i pacients amb esquizofrènia. En segon lloc, oferim una revisió sobre com les HARs sustenten les característiques del neurodesenvolupament humà, la configuració cerebral, el funcionament i la susceptibilitat per als trastorns psiquiàtrics Així mateix, informem de l'efecte modulador de la poligenicitat de les HARs sobre les diferències en l’arquitectura cortical en l'esquizofrènia i proporcionem evidències sobre l’especial rellevància de les HARs associades amb elements reguladors de la transcripció actius durant l’etapa fetal. De manera global, els resultats d’aquesta tesi indiquen que els fonaments etiològics de l’esquizofrènia estan relacionats amb diferències genètiques individuals que impacten en les trajectòries del neurodesenvolupament i les vies de plasticitat sinàptica, així com amb la composició genòmica que ens defineix com a espècie. Aquesta tesi aporta una gota en l’oceà del coneixement sobre els trastorns intrínsecament vinculats a la condició humana i ha pretès contribuir en la comprensió de les característiques úniques del nostre cervell per ajudar a entendre què vol dir ser humà.[spa] La esquizofrenia es un trastorno psiquiátrico que afecta a 24 millones de personas en todo el mundo. A pesar de que empezamos a conocer los mecanismos biológicos implicados en el origen del trastorno, los procesos etiológicos precisos continúan siendo en gran parte desconocidos. Por ello, los esfuerzos investigadores todavía necesitan dirigirse en mejorar el conocimiento de los fundamentos biológicos del trastorno, para así conseguir una mayor precisión en el diagnóstico y desarrollar nuevas estrategias terapéuticas que mejoren la calidad de vida de los pacientes. La hipótesis etiopatogénica predominante considera que el trastorno se origina de la interacción entre factores genéticos y ambientales que modifican los mecanismos perfectamente orquestados que guían el neurodesarrollo. Además, desde una perspectiva evolutiva, se sostiene que la esquizofrenia representa “el precio a pagar” por la evolución de los procesos ontogénicos específicamente humanos que sustentan la complejidad y la variabilidad inherente al funcionamiento del cerebro, así como la cognición y comportamiento de nuestra especie. A lo largo del neurodesarrollo, la formación de sinapsis y la organización y maduración de los circuitos neurales anclan la aparición de funciones cerebrales corticales distintivamente humanas. Por su parte, evidencias multidisciplinares indican que las alteraciones sinápticas participan en disfunciones cerebrales asociadas a la aparición de los síntomas cognitivos y clínicos de la esquizofrenia. En consecuencia, se ha propuesto que las alteraciones de la plasticidad sináptica tienen un papel crítico en la fisiopatología del trastorno. Entre los genes que confluyen en vías del neurodesarrollo y de plasticidad sináptica, hay genes que participan en vías de señalización implicadas en la homeostasis neuronal, el desarrollo de las espinas dendríticas y la excitabilidad neural, como el KCNH2, el DISC1, el CACNA1C y el ZNF804A, todos ellos previamente asociados con el riesgo para la esquizofrenia. Además, aproximaciones evolutivas han identificado regiones que han acumulado cambios específicamente humanos desde la divergencia con los chimpancés, como las Regiones Humanas Aceleradas (o Human Accelerated Regions, HARs en inglés). Estas regiones actúan como elementos reguladores de la transcripción otorgando características únicas al neurodesarrollo humano, y albergan variantes genéticas de susceptibilidad para la esquizofrenia. Para facilitar la identificación de los mecanismo genéticos y biológicos implicados en la etiología del trastorno, el uso de fenotipos cerebrales intermedios, como medidas de neuroimagen funcional y estructural, es una herramienta de gran valor. Siguiendo dos aproximaciones centradas en el análisis de los correlatos genético- fenotípicos entre genes candidatos relacionados con la plasticidad sináptica y secuencias HARs y las alteraciones cerebrales en la esquizofrenia, esta tesis incluye cuatro artículos originales y una revisión sistemática. En estos artículos, exponemos el efecto de polimorfismos en los genes KCNH2, DISC1, CACNA1C y ZNF804A y la carga poligénica en conjuntos informativos de HARs sobre las diferencias observadas entre cerebros sanos y cerebros con esquizofrenia. En su conjunto, los resultados validan la efectividad de los fenotipos de neuroimagen para identificar los mecanismos genéticos de la esquizofrenia y ponen de manifiesto la complementariedad de las aproximaciones centradas tanto en genes candidatos como en la variabilidad global del genoma para estudiar la arquitectura genética del trastorno. Primero describimos el papel de la variabilidad genética de los genes KCNH2 y DISC1 en la modulación de la respuesta funcional a la atención y la memoria de trabajo de manera condicional al diagnóstico. Además, identificamos que la epistasis entre dos genes asociados con la esquizofrenia a nivel de GWAS, el CACNAC1C y el ZNF804A, influye en la capacidad funcional de cerebro para adaptarse al incremento de requerimientos cognitivos en memoria de trabajo tanto en controles sanos como en pacientes con esquizofrenia. En segundo lugar, ofrecemos una revisión sobre cómo las HARs sustentan las características del neurodesarrollo humano, la configuración y el funcionamiento cerebral y la susceptibilidad para trastornos psiquiátricos. Así mismo, informamos del efecto modulador de la poligenicidad de las HARs sobre las diferencias en la arquitectura cortical en la esquizofrenia y proporcionamos evidencias sobre la especial relevancia de las HARs asociadas con elementos reguladores de la transcripción activos durante la etapa fetal. De manera global, los resultados de esta tesis indican que los fundamentos etiológicos de la esquizofrenia están relacionados con diferencias genéticas individuales que impactan en las trayectorias del neurodesarrollo y en las vías de plasticidad sináptica, así como en la composición genética que nos define como especie. Esta tesis aporta una gota en el océano del conocimiento sobre los trastornos intrínsicamente vinculados a la condición humana y ha pretendido contribuir en la comprensión de las características únicas de nuestro cerebro para ayudar a entender qué quiere decir ser humano

Analysis of the impact of synaptic plasticity genes and Human Accelerated Regions on brain function and structure: from the healthy brain to schizophrenia

[eng] Schizophrenia is a severe psychiatric disorder affecting around 24 million people worldwide. While we begin to disentangle the biological actors implicated in the origin of the disorder, the precise aetiological mechanisms remain largely unknown. Therefore, psychiatry research efforts still need to focus on a better understanding of the complex biological foundations of the disorder to achieve more precise diagnoses and the development of novel therapeutic strategies improving the patients’ quality of life. The prevailing etiopathological hypothesis considers that schizophrenia originates from the interplay between subtle genetic and environmental insults that disrupt the perfectly orchestrated mechanisms guiding neurodevelopment. Additionally, from an evolutionary perspective, it is suggested that schizophrenia represents a costly trade-off in the evolution of human-specific ontogenic neurodevelopmental processes sustaining the inherent complexity and variability of brain functioning, cognition, and behaviour. Along the neurodevelopmental process, the synapse formation and the organisation and maturation of neural circuits anchor the emergence of distinctive human cortical brain functions. In turn, multidisciplinary evidence indicates that synaptic alterations participate in brain dysfunctions, eventually leading to the emergence of the symptoms and cognitive deficits of schizophrenia. Accordingly, it is suggested that synaptic plasticity impairments play a critical role in the pathophysiology of the disorder. Among genes converging in neurodevelopmental and synaptic plasticity pathways, there are genes mediating signalling pathways involved in neural homeostasis, dendritic spine development and neural excitability, such as KCNH2, DISC1, CACNA1C and ZNF804A, all of them previously associated with the risk for schizophrenia. Moreover, evolutionary approaches have identified regions that accumulated human-specific changes since the divergence from chimpanzees, like Human Accelerated Regions (HARs). These regions act as transcriptional regulatory elements that endow human neurodevelopment with unique characteristics and harbour schizophrenia genetic susceptibility variants. To facilitate the identification of the genetic and biological mechanisms involved in schizophrenia aetiology, the use of brain-based intermediate phenotypes is a valuable strategy. Following two approaches centred on the genetic-phenotypic correlates of synaptic plasticity candidate genes and HARs sequences in the brain-based alterations in schizophrenia, this thesis includes four original articles and one systematic review. In these articles, we report the effect of common polymorphisms in KCNH2, DISC1, CACNA1C and ZNF804A genes and the polygenic load of HARs-informative sets on the differences observed between healthy brains and brains with schizophrenia. Overall, the results validate the efficacy of neuroimaging phenotypes to identify the genetic determinants of schizophrenia and point out the complementarity of candidate genes and genome-wide approaches in the study of the genetic architecture of the disorder. First, we describe the role of KCNH2 and DISC1 genetic variability in modulating the attentional and working memory-related functional responses in a diagnosis- dependent manner. Furthermore, we identify that the epistasis between two schizophrenia GWAS-associated genes, CACNAC1C and ZNF804A, influence the functional ability to adapt to increased working memory difficulty euqally in healthy controls and patients with schizophrenia. Second, we present a review of how HARs underlie human neurodevelopmental signatures, brain configuration, functioning and susceptibility behind psychiatric disorders. Likewise, we report the modulatory effect of HARs polygenicity on brain cortical architectural differences in schizophrenia and provide evidence on the importance of foetal-active regulatory HARs in patients' cortical surface area variability. Globally, the findings exposed in this thesis point towards the fact that the aetiological foundations of schizophrenia are related to the individual genetic differences altering neurodevelopment and synaptic plasticity trajectories but also to the genomic make-up that defines us as a species. This thesis provides a drop in the ocean of knowledge on disorders inherently linked to the human condition and has sought to comprehend the unique characteristics of our brain to help unravel what it means to be human.[cat] L’esquizofrènia és un trastorn neuropsiquiàtric greu que afecta a 24 milions de persones a tot el món. Tot i que comencem a conèixer els mecanismes biològics implicats en l’origen del trastorn, els processos etiològics precisos continuen essent en gran part desconeguts. Per tant, els esforços en la recerca encara necessiten dirigir-se en millorar el coneixement dels fonaments biològics del trastorn, per tal d’aconseguir un diagnòstic més precís i el desenvolupament de noves estratègies terapèutiques que millorin la qualitat de vida dels pacients. La hipòtesi etiopatogènica predominant considera que el trastorn s’origina a partir de la interacció entre factors genètics i ambientals que pertorben els mecanismes perfectament orquestrats que guien el neurodesenvolupament. A més, des d’una perspectiva evolutiva, s’ha suggerit que l’esquizofrènia representaria el “preu a pagar” per evolució dels processos ontogènics específicament humans que sustenten la complexitat i la variabilitat inherent al funcionament del cervell, la cognició i el comportament de la nostra espècie. Al llarg del neurodevenvolupament, la formació de sinapsis i l’organització i maduració dels circuits neurals ancoren l’aparició de funcions cerebrals corticals distintivament humanes. Al seu torn, evidències multidisciplinàries indiquen que les alteracions sinàptiques participen en disfuncions cerebrals que tenen com a resultat l’aparició dels símptomes cognitius i clínics de l’esquizofrènia. En conseqüència, s’ha proposat que les alteracions de la plasticitat sinàptica tenen un paper crític en la fisiopatologia del trastorn. Entre els gens que conflueixen en vies del neurodesenvolupament i de plasticitat sinàptica, hi ha gens que participen en vies de senyalització implicades en l’homeòstasi neuronal, el desenvolupament de les espines dendrítiques i l’excitabilitat neuronal, com els gens KCNH2, el DISC1, el CACNA1C i el ZNF804A, tots prèviament associats amb el risc per a l’esquizofrènia. A més, aproximacions evolutives han identificat regions que han acumulat canvis específicament en humans des de la divergència amb els ximpanzés, com les Regions Humanes Accelerades (o Human Accelerated Regions, HARs en anglès). Aquestes regions actuen com a elements reguladors de la transcripció atorgant característiques úniques al neurodesenvolupament humà, i contenen variants genètiques de susceptibilitat per a l’esquizofrènia. Per tal de facilitar l’identificar els mecanismes genètics i biològics implicats en l’etiologia de l’esquizofrènia, la utilització de fenotips cerebrals intermedis, com mesures de neuroimatge funcional i estructural, representa una estratègia molt útil. Seguint dues aproximacions centrades en l’anàlisi dels correlats genètics-fenotípics entre gens candidats relacionats amb la plasticitat sinàptica i regions HARs i les alteracions cerebrals de l’esquizofrènia, aquesta tesi inclou quatre articles originals i una revisió sistemàtica. En aquests articles, exposem l’efecte de polimorfismes en els gens KCNH2, DISC1, CACNA1C i ZNF804A i la càrrega poligènica en conjunts informatius de HARs sobre les diferències observades entre cervells de persones sanes i persones amb esquizofrènia. En conjunt, els resultats validen l’efectivitat dels fenotips de neuroimatge per identificar els determinants genètics de l’esquizofrènia i posen de manifest la complementarietat de les aproximacions centrades tant en gens candidats com en la variabilitat global del genoma per a l’estudi de l’arquitectura genètica del trastorn. Primer, descrivim el paper de la variabilitat genètica dels genes KCNH2 i DISC1 en la modulació de la resposta funcional a l’atenció i la memòria de treball de manera condicionada al diagnòstic. També, identifiquem que l’epistasi entre dos gens associats amb l’esquizofrènia a nivell de GWAS, el CACNAC1C i el ZNF804A, influeix en la capacitat funcionalde cervell per adaptar-se a l’increment de requeriments cognitius en memòria de treball en controls sans i pacients amb esquizofrènia. En segon lloc, oferim una revisió sobre com les HARs sustenten les característiques del neurodesenvolupament humà, la configuració cerebral, el funcionament i la susceptibilitat per als trastorns psiquiàtrics Així mateix, informem de l'efecte modulador de la poligenicitat de les HARs sobre les diferències en l’arquitectura cortical en l'esquizofrènia i proporcionem evidències sobre l’especial rellevància de les HARs associades amb elements reguladors de la transcripció actius durant l’etapa fetal. De manera global, els resultats d’aquesta tesi indiquen que els fonaments etiològics de l’esquizofrènia estan relacionats amb diferències genètiques individuals que impacten en les trajectòries del neurodesenvolupament i les vies de plasticitat sinàptica, així com amb la composició genòmica que ens defineix com a espècie. Aquesta tesi aporta una gota en l’oceà del coneixement sobre els trastorns intrínsecament vinculats a la condició humana i ha pretès contribuir en la comprensió de les característiques úniques del nostre cervell per ajudar a entendre què vol dir ser humà.[spa] La esquizofrenia es un trastorno psiquiátrico que afecta a 24 millones de personas en todo el mundo. A pesar de que empezamos a conocer los mecanismos biológicos implicados en el origen del trastorno, los procesos etiológicos precisos continúan siendo en gran parte desconocidos. Por ello, los esfuerzos investigadores todavía necesitan dirigirse en mejorar el conocimiento de los fundamentos biológicos del trastorno, para así conseguir una mayor precisión en el diagnóstico y desarrollar nuevas estrategias terapéuticas que mejoren la calidad de vida de los pacientes. La hipótesis etiopatogénica predominante considera que el trastorno se origina de la interacción entre factores genéticos y ambientales que modifican los mecanismos perfectamente orquestados que guían el neurodesarrollo. Además, desde una perspectiva evolutiva, se sostiene que la esquizofrenia representa “el precio a pagar” por la evolución de los procesos ontogénicos específicamente humanos que sustentan la complejidad y la variabilidad inherente al funcionamiento del cerebro, así como la cognición y comportamiento de nuestra especie. A lo largo del neurodesarrollo, la formación de sinapsis y la organización y maduración de los circuitos neurales anclan la aparición de funciones cerebrales corticales distintivamente humanas. Por su parte, evidencias multidisciplinares indican que las alteraciones sinápticas participan en disfunciones cerebrales asociadas a la aparición de los síntomas cognitivos y clínicos de la esquizofrenia. En consecuencia, se ha propuesto que las alteraciones de la plasticidad sináptica tienen un papel crítico en la fisiopatología del trastorno. Entre los genes que confluyen en vías del neurodesarrollo y de plasticidad sináptica, hay genes que participan en vías de señalización implicadas en la homeostasis neuronal, el desarrollo de las espinas dendríticas y la excitabilidad neural, como el KCNH2, el DISC1, el CACNA1C y el ZNF804A, todos ellos previamente asociados con el riesgo para la esquizofrenia. Además, aproximaciones evolutivas han identificado regiones que han acumulado cambios específicamente humanos desde la divergencia con los chimpancés, como las Regiones Humanas Aceleradas (o Human Accelerated Regions, HARs en inglés). Estas regiones actúan como elementos reguladores de la transcripción otorgando características únicas al neurodesarrollo humano, y albergan variantes genéticas de susceptibilidad para la esquizofrenia. Para facilitar la identificación de los mecanismo genéticos y biológicos implicados en la etiología del trastorno, el uso de fenotipos cerebrales intermedios, como medidas de neuroimagen funcional y estructural, es una herramienta de gran valor. Siguiendo dos aproximaciones centradas en el análisis de los correlatos genético- fenotípicos entre genes candidatos relacionados con la plasticidad sináptica y secuencias HARs y las alteraciones cerebrales en la esquizofrenia, esta tesis incluye cuatro artículos originales y una revisión sistemática. En estos artículos, exponemos el efecto de polimorfismos en los genes KCNH2, DISC1, CACNA1C y ZNF804A y la carga poligénica en conjuntos informativos de HARs sobre las diferencias observadas entre cerebros sanos y cerebros con esquizofrenia. En su conjunto, los resultados validan la efectividad de los fenotipos de neuroimagen para identificar los mecanismos genéticos de la esquizofrenia y ponen de manifiesto la complementariedad de las aproximaciones centradas tanto en genes candidatos como en la variabilidad global del genoma para estudiar la arquitectura genética del trastorno. Primero describimos el papel de la variabilidad genética de los genes KCNH2 y DISC1 en la modulación de la respuesta funcional a la atención y la memoria de trabajo de manera condicional al diagnóstico. Además, identificamos que la epistasis entre dos genes asociados con la esquizofrenia a nivel de GWAS, el CACNAC1C y el ZNF804A, influye en la capacidad funcional de cerebro para adaptarse al incremento de requerimientos cognitivos en memoria de trabajo tanto en controles sanos como en pacientes con esquizofrenia. En segundo lugar, ofrecemos una revisión sobre cómo las HARs sustentan las características del neurodesarrollo humano, la configuración y el funcionamiento cerebral y la susceptibilidad para trastornos psiquiátricos. Así mismo, informamos del efecto modulador de la poligenicidad de las HARs sobre las diferencias en la arquitectura cortical en la esquizofrenia y proporcionamos evidencias sobre la especial relevancia de las HARs asociadas con elementos reguladores de la transcripción activos durante la etapa fetal. De manera global, los resultados de esta tesis indican que los fundamentos etiológicos de la esquizofrenia están relacionados con diferencias genéticas individuales que impactan en las trayectorias del neurodesarrollo y en las vías de plasticidad sináptica, así como en la composición genética que nos define como especie. Esta tesis aporta una gota en el océano del conocimiento sobre los trastornos intrínsicamente vinculados a la condición humana y ha pretendido contribuir en la comprensión de las características únicas de nuestro cerebro para ayudar a entender qué quiere decir ser humano

Progress in defining the biological causes of schizophrenia

Schizophrenia is a common mental illness resulting from a complex interplay of genetic and environmental risk factors. Establishing its primary molecular and cellular aetiopathologies has proved difficult. However, this is a vital step towards the rational development of useful disease biomarkers and new therapeutic strategies. The advent and large-scale application of genomic, transcriptomic, proteomic and metabolomic technologies are generating data sets required to achieve this goal. This discovery phase, typified by its objective and hypothesis-free approach, is described in the first part of the review. The accumulating biological information, when viewed as a whole, reveals a number of biological process and subcellular locations that contribute to schizophrenia causation. The data also show that each technique targets different aspects of central nervous system function in the disease state. In the second part of the review, key schizophrenia candidate genes are discussed more fully. Two higher-order processes - adult neurogenesis and inflammation - that appear to have pathological relevance are also described in detail. Finally, three areas where progress would have a large impact on schizophrenia biology are discussed: deducing the causes of schizophrenia in the individual, explaining the phenomenon of cross-disorder risk factors, and distinguishing causative disease factors from those that are reactive or compensatory

Identification of novel risk loci for restless legs syndrome in genome-wide association studies in individuals of European ancestry : a meta-analysis

Background Restless legs syndrome is a prevalent chronic neurological disorder with potentially severe mental and physical health consequences. Clearer understanding of the underlying pathophysiology is needed to improve treatment options. We did a meta-analysis of genome-wide association studies (GWASs) to identify potential molecular targets. Methods In the discovery stage, we combined three GWAS datasets (EU-RLS GENE, INTERVAL, and 23andMe) with diagnosis data collected from 2003 to 2017, in face-to-face interviews or via questionnaires, and involving 15126 cases and 95 725 controls of European ancestry. We identified common variants by fixed-effect inverse-variance meta-analysis. Significant genome-wide signals (p Findings We identified and replicated 13 new risk loci for restless legs syndrome and confirmed the previously identified six risk loci. MEIS1 was confirmed as the strongest genetic risk factor for restless legs syndrome (odds ratio 1.92, 95% CI 1 85-1.99). Gene prioritisation, enrichment, and genetic correlation analyses showed that identified pathways were related to neurodevelopment and highlighted genes linked to axon guidance (associated with SEMA6D), synapse formation (NTNG1), and neuronal specification (HOXB cluster family and MYT1). Interpretation Identification of new candidate genes and associated pathways will inform future functional research. Advances in understanding of the molecular mechanisms that underlie restless legs syndrome could lead to new treatment options. We focused on common variants; thus, additional studies are needed to dissect the roles of rare and structural variations.Peer reviewe

Genetic common variants associated with cerebellar volume and their overlap with mental disorders: a study on 33,265 individuals from the UK-Biobank

Interest in the cerebellum is expanding given evidence of its contributions to cognition and emotion, and dysfunction in various psychopathologies. However, research into its genetic architecture and shared influences with liability for mental disorders is lacking. We conducted a genome-wide association study (GWAS) of total cerebellar volume and underlying cerebellar lobe volumes in 33,265 UK-Biobank participants. Total cerebellar volume was heritable (h2SNP = 50.6%), showing moderate genetic homogeneity across lobes (h2SNP from 35.4% to 57.1%; mean genetic correlation between lobes rg ≈ 0.44). We identified 33 GWAS signals associated with total cerebellar volume, of which 6 are known to alter protein-coding gene structure, while a further five mapped to genomic regions known to alter cerebellar tissue gene expression. Use of summary data-based Mendelian randomisation further prioritised genes whose change in expression appears to mediate the SNP-trait association. In total, we highlight 21 unique genes of greatest interest for follow-up analyses. Using LD-regression, we report significant genetic correlations between total cerebellar volume and brainstem, pallidum and thalamus volumes. While the same approach did not result in significant correlations with psychiatric phenotypes, we report enrichment of schizophrenia, bipolar disorder and autism spectrum disorder associated signals within total cerebellar GWAS results via conditional and conjunctional-FDR analysis. Via these methods and GWAS catalogue, we identify which of our cerebellar genomic regions also associate with psychiatric traits. Our results provide important insights into the common allele architecture of cerebellar volume and its overlap with other brain volumes and psychiatric phenotypes

The relationship between genetic risk variants with brain structure and function in bipolar disorder: A systematic review of genetic-neuroimaging studies

Genetic-neuroimaging paradigms could provide insights regarding the pathophysiology of bipolar disorder (BD). Nevertheless, findings have been inconsistent across studies. A systematic review of gene-imaging studies involving individuals with BD was conducted across electronic major databases from inception until January 9th, 2017. Forty-four studies met eligibility criteria (N=2122 BD participants). Twenty-six gene variants were investigated across candidate gene studies and 4 studies used a genome-wide association approach. Replicated evidence (i.e. in >2 studies) suggests that individuals with BD carrying the BDNF Val66Met risk allele could have reduced hippocampal volumes compared to non-carriers. This review underscores the potential of gene-neuroimaging paradigms to provide mechanistic insights for BD. However, this systematic review found a single replicated finding. Suggestions to improve the reproducibility of this emerging field are provided, including the adoption of a trans-diagnostic approac