Factors de risc genètics implicats en el deteriorament cognitiu en malalties neurodegeneratives

Els canvis evolutius en l’espècie humana, i en concret en el cervell, han permès que els humans hagin desenvolupat una capacitat d’aprenentatge i memòria sense precedents. En un marc multidisciplinari de l’evolució humana, l’arqueologia, la genètica i la medicina són disciplines que convergeixen en la recerca científica de l’evolució cerebral. Per entendre els canvis que s’han produït en el cervell humà, aquesta Tesi dóna un enfocament partint de l’evolució del cervell fins a la vulnerabilitat a patir malalties neurodegeneratives que afecten, principalment, la capacitat de memòria. L’objectiu d’aquest treball ha estat aportar coneixements en la capacitat cognitiva humana, concretament en la cerca de factors de risc genètics implicats en processos de deteriorament cognitiu i pèrdua de memòria. Els dos gens d’estudi en aquest treball són el gen de microtúbols associats a proteïna TAU (MAPT) i el gen de la β-glucocerebrosidasa (GBA). Existeixen nombrosos estudis publicats que associen aquests gens amb el deteriorament cognitiu. Per dur a terme el treball, inicialment es van recollir mostres de pacients acuradament diagnosticats en malalties neurodegeneratives (malaltia d’Alzheimer i malaltia de Parkinson) i també es van recollir mostres d’individus sans per realitzar l’estudi. Per enriquir evolutivament aquest treball, s’ha completat l’anàlisi de les variants del gen MAPT en homínids ancestrals (Homo neanderthalensis i homínid de Denisova) i grans simis mitjançant bases de dades disponibles a Internet. Les anàlisis dels gens MAPT i GBA donen com a resultat que existeixen variacions genètiques significatives entre pacients amb malalties neurodegeneratives amb demència respecte a individus sans. Els resultats també mostren que les mutacions i variants en aquests dos gens impliquen un augment del risc de demència en pacients respecte controls. En l’àmbit evolutiu, la comparació de la seqüència d’ADN del gen MAPT entre humans anatòmicament moderns, neandertals, homínid de Denisova i grans simis ha aportat diferències en la seqüència genòmica úniques entre els tres homínids. Els avenços tecnològics, com la seqüenciació nuclear d’ADN en diferents espècies d’homínids, podran esclarir en un futur qüestions cognitives referents als nostres avantpassat.Los cambios evolutivos en la especie humana, y en concreto en el cerebro, han permitido a los humanos desarrollar una capacidad de aprendizaje y memoria sin precedentes. En un marco multidisciplinar de la evolución humana, la arqueología, la genética y la medicina son disciplinas que convergen en el estudio científico de la evolución cerebral. Para entender los cambios que se han producido en el cerebro humano esta Tesis aporta un enfoque partiendo de la evolución cerebral hasta la vulnerabilidad al desarrollo de enfermedades neurodegenerativas, que afectan principalmente, la capacidad de memoria. El objetivo de este trabajo ha sido aportar conocimientos en la capacidad cognitiva humana, concretamente en la búsqueda de factores de riesgo genéticos implicados en los procesos de deterioro cognitivo y pérdida de memoria. Los dos genes de estudio en este trabajo son, el gen de los microtúbulos asociados a proteína TAU (MAPT) i el gen de la β-glucocerebrosidasa (GBA). Existen muchos estudios de asocian con estos genes al deterioro cognitivo. Para desarrollar este trabajo, inicialmente se recogieron muestras de pacientes cuidadosamente diagnosticados en enfermedades neurodegenerativas (enfermedad de Alzheimer y enfermedad de Parkinson) y también se recogieron muestras de individuos sanos para realizar el estudio. Para enriquecer evolutivamente el trabajo, se completó el análisis de las variantes del gen MAPT en homínidos ancestrales (Homo neanderthalensis y el homínido de Denisova) y grandes simios, mediante bases de datos disponibles en internet. Los análisis de los genes de MAPT y GBA dan como resultado que existen variaciones genéticas significativas entre pacientes con enfermedades neurodegenerativas con demencia respecto a individuos sanos. El resultado también muestra que las mutaciones y variantes de estos genes implican un aumento de riesgo de demencia en pacientes respecto controles. En relación a la evolución, la comparación de la secuencia de ADN del gen MAPT entre humanos anatómicamente modernos, neandertales y el homínido de Denisova y grandes simios aporta diferencias en la secuencia genómica únicas entre los tres homínidos. Los avances tecnológicos, como la secuenciación nuclear del ADN en diferentes especies de homínidos podrá esclarecer en un futuro cuestiones cognitivas de nuestro pasado

Using the Neandertal and Denisova Genetic Data to Understand the Common \u3cem\u3eMAPT\u3c/em\u3e 17q21 Inversion in Modern Humans

The polymorphic inversion on 17q21, that includes the MAPT gene, represents a unique locus in the human genome characterized by a large region with strong linkage disequilibrium. Two distinct haplotypes, H1 and H2, exist in modern humans, and H1 has been unequivocally related to several neurodegenerative disorders. Recent data indicates that recurrent inversions of this genomic region have occurred through primate evolution, with the H2 haplotype being the ancestral state. Neandertals harbored the H1 haplotype, however until now no data was available for the Denisova hominin. Neandertals and Denisovans are sister groups that share a common ancestor with modern humans. We analyzed the MAPT sequence and assessed the differences between modern humans, Neandertals, Denisovans, and great apes. Our analysis indicated that the Denisova hominin carried the H1 haplotype and the Neandertal and Denisova common ancestor probably shared the same subhaplotype (H1j). We also found 68 intronic variants within the MAPT gene, 23 exclusive to Denisova hominin, 6 limited to Neandertals and 24 exclusive to present-day humans. Our results reinforce previous data suggesting that the 17q21 inversion arose within the modern human lineage. The data also indicates that archaic hominins that coexisted in Eurasia probably shared the same MAPT subhaplotype, hat can be found in almost 2% of chromosomes from European ancestry

Developmental regulation of tau splicing is disrupted in stem cell-derived neurons from frontotemporal dementia patients with the 10 + 16 splice-site mutation in MAPT

The alternative splicing of the tau gene, MAPT, generates six protein isoforms in the adult human CNS. Tau splicing is developmentally regulated and dysregulated in disease. Mutations in MAPT that alter tau splicing cause frontotemporal dementia (FTD) with tau pathology, providing evidence for a causal link between altered tau splicing and disease. The use of induced pluripotent stem cell (iPSC) derived neurons has revolutionized the way we model neurological disease in vitro. However, as most tau mutations are located within or around the alternatively spliced exon 10, it is important that iPSC-neurons splice tau appropriately in order to be used as disease models. To address this issue, we analysed the expression, and splicing of tau in iPSC-derived cortical neurons from control patients and FTD patients with the 10+16 intronic mutation in MAPT. We show that control neurons only express the fetal tau isoform (0N3R), even at extended time points of 100 days in vitro. Neurons from FTD patients with the 10+16 mutation in MAPT express both 0N3R and 0N4R tau isoforms, demonstrating that this mutation overrides the developmental regulation of exon 10 inclusion in our in vitro model. Further, at extended time-points of 365 days in vitro, we observe a switch in tau splicing to include six tau isoforms as seen the adult human CNS. Our results demonstrate the importance of neuronal maturity for use in in vitro modeling and provide a system that will be important for understanding the functional consequences of altered tau splicing

Fulminant corticobasal degeneration: a distinct variant with predominant neuronal tau aggregates.

Corticobasal degeneration typically progresses gradually over 5-7 years from onset till death. Fulminant corticobasal degeneration cases with a rapidly progressive course were rarely reported (RP-CBD). This study aimed to investigate their neuropathological characteristics. Of the 124 autopsy-confirmed corticobasal degeneration cases collected from 14 centres, we identified 6 RP-CBD cases (4.8%) who died of advanced disease within 3 years of onset. These RP-CBD cases had different clinical phenotypes including rapid global cognitive decline (N = 2), corticobasal syndrome (N = 2) and Richardson's syndrome (N = 2). We also studied four corticobasal degeneration cases with an average disease duration of 3 years or less, who died of another unrelated illness (Intermediate-CBD). Finally, we selected 12 age-matched corticobasal degeneration cases out of a cohort of 110, who had a typical gradually progressive course and reached advanced clinical stage (End-stage-CBD). Quantitative analysis showed high overall tau burden (p = 0.2) and severe nigral cell loss (p = 0.47) in both the RP-CBD and End-stage-CBD groups consistent with advanced pathological changes, while the Intermediate-CBD group (mean disease duration = 3 years) had milder changes than End-stage-CBD (p < 0.05). These findings indicated that RP-CBD cases had already developed advanced pathological changes as those observed in End-stage-CBD cases (mean disease duration = 6.7 years), but within a significantly shorter duration (2.5 years; p < 0.001). Subgroup analysis was performed to investigate the cellular patterns of tau aggregates in the anterior frontal cortex and caudate by comparing neuronal-to-astrocytic plaque ratios between six RP-CBD cases, four Intermediate-CBD and 12 age-matched End-stage-CBD. Neuronal-to-astrocytic plaque ratios of Intermediate-CBD and End-stage-CBD, but not RP-CBD, positively correlated with disease duration in both the anterior frontal cortex and caudate (p = 0.02). In contrast to the predominance of astrocytic plaques we previously reported in preclinical asymptomatic corticobasal degeneration cases, neuronal tau aggregates predominated in RP-CBD exceeding those in Intermediate-CBD (anterior frontal cortex: p < 0.001, caudate: p = 0.001) and End-stage-CBD (anterior frontal cortex: p = 0.03, caudate: p = 0.01) as demonstrated by its higher neuronal-to-astrocytic plaque ratios in both anterior frontal cortex and caudate. We did not identify any difference in age at onset, any pathogenic tau mutation or concomitant pathologies that could have contributed to the rapid progression of these RP-CBD cases. Mild TDP-43 pathology was observed in three RP-CBD cases. All RP-CBD cases were men. The MAPT H2 haplotype, known to be protective, was identified in one RP-CBD case (17%) and 8 of the matched End-stage-CBD cases (67%). We conclude that RP-CBD is a distinct aggressive variant of corticobasal degeneration with characteristic neuropathological substrates resulting in a fulminant disease process as evident both clinically and pathologically. Biological factors such as genetic modifiers likely play a pivotal role in the RP-CBD variant and should be the subject of future research

Using the Neandertal and Denisova genetic data to understand the common MAPT 17q21 inversion in modern humans

The polymorphic inversion on 17q21, that includes the MAPT gene, represents a unique locus in the human genome characterized by a large region with strong linkage disequilibrium. Two distinct haplotypes, H1 and H2, exist in modern humans, and H1 has been unequivocally related to several neurodegenerative disorders. Recent data indicate that recurrent inversions of this genomic region have occurred through primate evolution, with the H2 haplotype being the ancestral state. Neandertals harbored the H1 haplotype; however, until now, no data were available for the Denisova hominin. Neandertals and Denisovans are sister groups that share a common ancestor with modern humans. We analyzed the MAPT sequence and assessed the differences between modern humans, Neandertals, Denisovans, and great apes. Our analysis indicated that the Denisova hominin carried the H1 haplotype, and the Neandertal and Denisova common ancestor probably shared the same subhaplotype (H1j). We also found 68 intronic variants within the MAPT gene, 23 exclusive to Denisova hominin, 6 limited to Neandertals, and 24 exclusive to present-day humans. Our results reinforce previous data; this suggests that the 17q21 inversion arose within the modern human lineage. The data also indicate that archaic hominins that coexisted in Eurasia probably shared the same MAPT subhaplotype, and this can be found in almost 2% of chromosomes from European ancestry. © 2013 Wayne State University Press.Peer Reviewe

Using the Neandertal and Denisova Genetic Data to Understand the Common MAPT 17q21 Inversion in Modern Humans

Abstract The polymorphic inversion on 17q21, that includes the MAPT gene, represents a unique locus in the human genome characterized by a large region with strong linkage disequilibrium. Two distinct haplotypes, H1 and H2, exist in modern humans, and H1 has been unequivocally related to several neurodegenerative disorders. Recent data indicate that recurrent inversions of this genomic region have occurred through primate evolution, with the H2 haplotype being the ancestral state. Neandertals harbored the H1 haplotype; however, until now, no data were available for the Denisova hominin. Neandertals and Denisovans are sister groups that share a common ancestor with modern humans. We analyzed the MAPT sequence and assessed the differences between modern humans, Neandertals, Denisovans, and great apes. Our analysis indicated that the Denisova hominin carried the H1 haplotype, and the Neandertal and Denisova common ancestor probably shared the same subhaplotype (H1j). We also found 68 intronic variants within the MAPT gene, 23 exclusive to Denisova hominin, 6 limited to Neandertals, and 24 exclusive to present-day humans. Our results reinforce previous data; this suggests that the 17q21 inversion arose within the modern human lineage. The data also indicate that archaic hominins that coexisted in Eurasia probably shared the same MAPT subhaplotype, and this can be found in almost 2% of chromosomes from European ancestry

Fulminant corticobasal degeneration: a distinct variant with predominant neuronal tau aggregates.

Corticobasal degeneration typically progresses gradually over 5-7 years from onset till death. Fulminant corticobasal degeneration cases with a rapidly progressive course were rarely reported (RP-CBD). This study aimed to investigate their neuropathological characteristics. Of the 124 autopsy-confirmed corticobasal degeneration cases collected from 14 centres, we identified 6 RP-CBD cases (4.8%) who died of advanced disease within 3 years of onset. These RP-CBD cases had different clinical phenotypes including rapid global cognitive decline (N = 2), corticobasal syndrome (N = 2) and Richardson's syndrome (N = 2). We also studied four corticobasal degeneration cases with an average disease duration of 3 years or less, who died of another unrelated illness (Intermediate-CBD). Finally, we selected 12 age-matched corticobasal degeneration cases out of a cohort of 110, who had a typical gradually progressive course and reached advanced clinical stage (End-stage-CBD). Quantitative analysis showed high overall tau burden (p = 0.2) and severe nigral cell loss (p = 0.47) in both the RP-CBD and End-stage-CBD groups consistent with advanced pathological changes, while the Intermediate-CBD group (mean disease duration = 3 years) had milder changes than End-stage-CBD (p < 0.05). These findings indicated that RP-CBD cases had already developed advanced pathological changes as those observed in End-stage-CBD cases (mean disease duration = 6.7 years), but within a significantly shorter duration (2.5 years; p < 0.001). Subgroup analysis was performed to investigate the cellular patterns of tau aggregates in the anterior frontal cortex and caudate by comparing neuronal-to-astrocytic plaque ratios between six RP-CBD cases, four Intermediate-CBD and 12 age-matched End-stage-CBD. Neuronal-to-astrocytic plaque ratios of Intermediate-CBD and End-stage-CBD, but not RP-CBD, positively correlated with disease duration in both the anterior frontal cortex and caudate (p = 0.02). In contrast to the predominance of astrocytic plaques we previously reported in preclinical asymptomatic corticobasal degeneration cases, neuronal tau aggregates predominated in RP-CBD exceeding those in Intermediate-CBD (anterior frontal cortex: p < 0.001, caudate: p = 0.001) and End-stage-CBD (anterior frontal cortex: p = 0.03, caudate: p = 0.01) as demonstrated by its higher neuronal-to-astrocytic plaque ratios in both anterior frontal cortex and caudate. We did not identify any difference in age at onset, any pathogenic tau mutation or concomitant pathologies that could have contributed to the rapid progression of these RP-CBD cases. Mild TDP-43 pathology was observed in three RP-CBD cases. All RP-CBD cases were men. The MAPT H2 haplotype, known to be protective, was identified in one RP-CBD case (17%) and 8 of the matched End-stage-CBD cases (67%). We conclude that RP-CBD is a distinct aggressive variant of corticobasal degeneration with characteristic neuropathological substrates resulting in a fulminant disease process as evident both clinically and pathologically. Biological factors such as genetic modifiers likely play a pivotal role in the RP-CBD variant and should be the subject of future research

Fulminant corticobasal degeneration: a distinct variant with predominant neuronal tau aggregates

Corticobasal degeneration typically progresses gradually over 5–7 years from onset till death. Fulminant corticobasal degeneration cases with a rapidly progressive course were rarely reported (RP-CBD). This study aimed to investigate their neuropathological characteristics. Of the 124 autopsy-confirmed corticobasal degeneration cases collected from 14 centres, we identified 6 RP-CBD cases (4.8%) who died of advanced disease within 3 years of onset. These RP-CBD cases had different clinical phenotypes including rapid global cognitive decline (N = 2), corticobasal syndrome (N = 2) and Richardson’s syndrome (N = 2). We also studied four corticobasal degeneration cases with an average disease duration of 3 years or less, who died of another unrelated illness (Intermediate-CBD). Finally, we selected 12 age-matched corticobasal degeneration cases out of a cohort of 110, who had a typical gradually progressive course and reached advanced clinical stage (End-stage-CBD). Quantitative analysis showed high overall tau burden (p = 0.2) and severe nigral cell loss (p = 0.47) in both the RP-CBD and End-stage-CBD groups consistent with advanced pathological changes, while the Intermediate-CBD group (mean disease duration = 3 years) had milder changes than End-stage-CBD (p &lt; 0.05). These findings indicated that RP-CBD cases had already developed advanced pathological changes as those observed in End-stage-CBD cases (mean disease duration = 6.7 years), but within a significantly shorter duration (2.5 years; p &lt; 0.001). Subgroup analysis was performed to investigate the cellular patterns of tau aggregates in the anterior frontal cortex and caudate by comparing neuronal-to-astrocytic plaque ratios between six RP-CBD cases, four Intermediate-CBD and 12 age-matched End-stage-CBD. Neuronal-to-astrocytic plaque ratios of Intermediate-CBD and End-stage-CBD, but not RP-CBD, positively correlated with disease duration in both the anterior frontal cortex and caudate (p = 0.02). In contrast to the predominance of astrocytic plaques we previously reported in preclinical asymptomatic corticobasal degeneration cases, neuronal tau aggregates predominated in RP-CBD exceeding those in Intermediate-CBD (anterior frontal cortex: p &lt; 0.001, caudate: p = 0.001) and End-stage-CBD (anterior frontal cortex: p = 0.03, caudate: p = 0.01) as demonstrated by its higher neuronal-to-astrocytic plaque ratios in both anterior frontal cortex and caudate. We did not identify any difference in age at onset, any pathogenic tau mutation or concomitant pathologies that could have contributed to the rapid progression of these RP-CBD cases. Mild TDP-43 pathology was observed in three RP-CBD cases. All RP-CBD cases were men. The MAPT H2 haplotype, known to be protective, was identified in one RP-CBD case (17%) and 8 of the matched End-stage-CBD cases (67%). We conclude that RP-CBD is a distinct aggressive variant of corticobasal degeneration with characteristic neuropathological substrates resulting in a fulminant disease process as evident both clinically and pathologically. Biological factors such as genetic modifiers likely play a pivotal role in the RP-CBD variant and should be the subject of future research

Rare variants in calcium homeostasis modulator 1 (CALHM1) found in early onset Alzheimer's disease patients alter calcium homeostasis.

Calcium signaling in the brain is fundamental to the learning and memory process and there is evidence to suggest that its dysfunction is involved in the pathological pathways underlying Alzheimer's disease (AD). Recently, the calcium hypothesis of AD has received support with the identification of the non-selective Ca2+-permeable channel CALHM1. A genetic polymorphism (p. P86L) in CALHM1 reduces plasma membrane Ca2+ permeability and is associated with an earlier age-at-onset of AD. To investigate the role of CALHM1 variants in early-onset AD (EOAD), we sequenced all CALHM1 coding regions in three independent series comprising 284 EOAD patients and 326 controls. Two missense mutations in patients (p.G330D and p.R154H) and one (p.A213T) in a control individual were identified. Calcium imaging analyses revealed that while the mutation found in a control (p.A213T) behaved as wild-type CALHM1 (CALHM1-WT), a complete abolishment of the Ca2+ influx was associated with the mutations found in EOAD patients (p.G330D and p.R154H). Notably, the previously reported p. P86L mutation was associated with an intermediate Ca2+ influx between the CALHM1-WT and the p.G330D and p.R154H mutations. Since neither expression of wild-type nor mutant CALHM1 affected amyloid ß-peptide (Aß) production or Aß-mediated cellular toxicity, we conclude that rare genetic variants in CALHM1 lead to Ca2+ dysregulation and may contribute to the risk of EOAD through a mechanism independent from the classical Aß cascad