Estudio genético en esquizofrenia: análisis de variantes funcionales para la identificación de factores de predisposición

La esquizofrenia es un trastorno psiquiátrico severo que afecta a poblaciones de todo el mundo, con una prevalencia cercana al 1%. La enfermedad se manifiesta de manera clara en la adolescencia o inicio de la edad adulta, y está asociada a una fertilidad reducida y a una elevada tasa de mortalidad. Se trata de una enfermedad compleja que resulta de una combinación de factores genéticos y ambientales, aunque la causa exacta de la enfermedad continúa siendo desconocida. Se ha estimado su heredabilidad en torno al 65-80%. El objetivo central de este trabajo de investigación ha sido la evaluación de variantes genéticas con alta probabilidad a priori de ser funcionales para la eventual identificación de variantes de susceptibilidad a padecer esquizofrenia con una funcionalidad clara. Atendiendo al modo en que hemos abordado la selección de variantes, el trabajo puede dividirse en dos partes. En la primera parte nos centramos en variantes que hubiesen sido objeto de selección natural reciente -y por tanto funcionalmente diferentes-, en genes candidatos. En la segunda etapa de esta tesis decidimos explorar sistemáticamente el papel de SNPs no sinónimos en la etiología de la enfermedad; este tipo de polimorfismos están localizados en exones e implican un cambio de aminoácido en las proteínas, por lo que presentan elevada probabilidad a priori de ser funcionales y de estar implicados en la aparición de enfermedades

Association of single nucleotide polymorphisms with renal cell carcinoma in Algerian population

Background: Renal cell carcinoma (RCC) is a common malignant tumor of the urinary system. The etiology of RCC is a complex interaction between environmental and multigenetic factors. Genome-wide association studies have iden? tifed new susceptibility risk loci for RCC. We examined associations of genetic variants of genes that are involved in metabolism, DNA repair and oncogenes with renal cancer risk. A total of 14 single nucleotide polymorphisms (SNPs) in 11 genes (VEGF, VHL, ATM, FAF1, LRRIQ4, RHOBTB2, OBFC1, DPF3, ALDH9A1 and EPAS1) were examined. Methods: The current case?control study included 87 RCC patients and 114 controls matched for age, gender and ethnic origin. The 14 tag-SNPs were genotyped by Sequenom MassARRAY? iPLEX using blood genomic DNA. Results: Genotype CG and allele G of ATM rs1800057 were signifcantly associated with RCC susceptibility (p=0.043; OR=8.47; CI=1.00?71.76). Meanwhile, we found that genotype AA of rs67311347 polymorphism could increase the risk of RCC (p=0.03; OR=2.95; IC=1.10?7.89). While, genotype TT and T allele of ALDH9A1 rs3845536 were observed to approach signifcance for a protective role against RCC (p=0.007; OR=0.26; CI=0.09?0.70). Conclusion: Our results indicate that ATM rs1800057 may have an efect on the risk of RCC, and suggest that ALDH9A1 was a protective factor against RCC in Algerian populatio

Identification of putative second genetic hits in schizophrenia carriers of high-risk copy number variants and resequencing in additional samples

Copy number variants (CNVs) conferring risk of schizophrenia present incomplete penetrance, suggesting the existence of second genetic hits. Identification of second hits may help to find genes with rare variants of susceptibility to schizophrenia. The aim of this work was to search for second hits of moderate/high risk in schizophrenia carriers of risk CNVs and resequencing of the relevant genes in additional samples. To this end, ten patients with risk CNVs at cytobands 15q11.2, 15q11.2-13.1, 16p11.2, or 16p13.11, were subjected to whole-exome sequencing. Rare single nucleotide variants, defined as those absent from main public databases, were classified according to bioinformatic prediction of pathogenicity by CADD scores. The average number of rare predicted pathogenic variants per sample was 13.6 (SD 2.01). Two genes, BFAR and SYNJ1, presented rare predicted pathogenic variants in more than one sample. Follow-up resequencing of these genes in 432 additional cases and 432 controls identified a significant excess of rare predicted pathogenic variants in case samples at SYNJ1. Taking into account its function in clathrin-mediated synaptic vesicle endocytosis at presynaptic terminals, our results suggest an impairment of this process in schizophrenia

Molecular Basis, Diagnostic Challenges and Therapeutic Approaches of Bartter and Gitelman Syndromes: A Primer for Clinicians

Gitelman and Bartter syndromes are rare inherited diseases that belong to the category of renal tubulopathies. The genes associated with these pathologies encode electrolyte transport proteins located in the nephron, particularly in the Distal Convoluted Tubule and Ascending Loop of Henle. Therefore, both syndromes are characterized by alterations in the secretion and reabsorption processes that occur in these regions. Patients suffer from deficiencies in the concentration of electrolytes in the blood and urine, which leads to different systemic consequences related to these salt-wasting processes. The main clinical features of both syndromes are hypokalemia, hypochloremia, metabolic alkalosis, hyperreninemia and hyperaldosteronism. Despite having a different molecular etiology, Gitelman and Bartter syndromes share a relevant number of clinical symptoms, and they have similar therapeutic approaches. The main basis of their treatment consists of electrolytes supplements accompanied by dietary changes. Specifically for Bartter syndrome, the use of non-steroidal anti-inflammatory drugs is also strongly supported. This review aims to address the latest diagnostic challenges and therapeutic approaches, as well as relevant recent research on the biology of the proteins involved in disease. Finally, we highlight several objectives to continue advancing in the characterization of both etiologies

Manejo de casos sospechosos de la nueva gripe AH1N1 por los servicios de emergencias móviles.

Los servicios de emergencias móviles son un eslabón clave en la clasificación, y manejo de casos sospechosos de nueva gripe AH1N1. Los mismos garantizan una racional asistencia dependiendo de la necesidad de la atención que requiera cada caso. Nuestro objetivo es mostrar la organización creada para la asistencia de estos pacientes. Se realizó una revisión de los protocolos propuestos por la organización mundial de la salud, el Centro de Control de Enfermedades de Atlanta y otras bibliografías nacionales sobre el manejo de pacientes ante epidemias. Se trataron los casos a partir de los hallazgos clínicos, complementarios y factores de riesgos, mejorando la clasificación en los servicios de urgencias y su traslado a centros adecuados para su atención. La clasificación adecuada de casos, elimina el margen de error en la coordinación, y garantiza una asistencia adecuada y traslado al centro con condiciones para el tratamiento de sus posibles complicaciones.  Palabras clave: Nueva gripe, servicios de emergencias móviles, móviles básicos, móviles avanzados

Common schizophrenia alleles are enriched in mutation-intolerant genes and maintained by background selection

Schizophrenia is a debilitating psychiatric condition often associated with poor quality of life and decreased life expectancy. Lack of progress in improving treatment outcomes has been attributed to limited knowledge of the underlying biology, although large-scale genomic studies have begun to provide such insight. We report the largest single cohort genome-wide association study of schizophrenia (11,260 cases and 24,542 controls) and through meta-analysis with existing data we identify 50 novel GWAS loci. Using gene-wide association statistics we implicate an additional set of 22 novel associations that map onto a single gene. We show for the first time that the common variant association signal is highly enriched among genes that are intolerant to loss of function mutations and that variants in these genes persist in the population despite the low fecundity associated with the disorder through the process of background selection. Associations point to novel areas of biology (e.g. metabotropic GABA-B signalling and acetyl cholinesterase), reinforce those implicated in earlier GWAS studies (e.g. calcium channel function), converge with earlier rare variants studies (e.g. NRXN1, GABAergic signalling), identify novel overlaps with autism (e.g. RBFOX1, FOXP1, FOXG1), and support early controversial candidate gene hypotheses (e.g. ERBB4 implicating neuregulin signalling). We also demonstrate the involvement of six independent central nervous system functional gene sets in schizophrenia pathophysiology. These findings provide novel insights into the biology and genetic architecture of schizophrenia, highlight the importance of mutation intolerant genes and suggest a mechanism by which common risk variants are maintained in the population

Targeted sequencing of 10,198 samples confirms abnormalities in neuronal activity and implicates voltage-gated sodium channels in schizophrenia pathogenesis

Background Sequencing studies have pointed to the involvement in schizophrenia of rare coding variants in neuronally expressed genes, including activity-regulated cytoskeleton-associated protein (ARC) and N-methyl-d-aspartate receptor (NMDAR) complexes; however, larger samples are required to reveal novel genes and specific biological mechanisms. Methods We sequenced 187 genes, selected for prior evidence of association with schizophrenia, in a new dataset of 5,207 cases and 4,991 controls. Included among these genes were members of ARC and NMDAR post-synaptic protein complexes, as well as voltage-gated sodium and calcium channels. We performed a rare variant meta-analysis with published sequencing data for a total of 11,319 cases, 15,854 controls and 1,136 trios. Results While no individual gene was significantly associated with schizophrenia after genome-wide correction for multiple testing, we strengthen the evidence that rare exonic variants in the synaptic complexes ARC (P = 4.0 x 10-4) and NMDAR (P = 1.7 x 10-5) are risk factors for schizophrenia. In addition, we found that LoF variants and missense variants at paralog conserved sites were enriched in voltage-gated sodium channels, particularly the alpha subunits (P = 8.6 x 10-4). Conclusions In one of the largest sequencing studies of schizophrenia to date, we provide novel evidence that multiple voltage-gated sodium channels are involved in schizophrenia pathogenesis and confirm the involvement of ARC and NMDAR post-synaptic complexes

De novo mutations identified by exome sequencing implicate rare missense variants in SLC6A1 in schizophrenia

Schizophrenia is a highly polygenic disorder with important contributions from both common and rare risk alleles. We analyzed exome sequencing data for de novo variants (DNVs) in a new sample of 613 schizophrenia trios and combined this with published data to give a total of 3,444 trios. In this new data, loss-of-function (LoF) DNVs were significantly enriched among 3,471 LoF-intolerant genes, which supports previous findings. In the full dataset, genes associated with neurodevelopmental disorders (n = 159) were significantly enriched for LoF DNVs. Within these neurodevelopmental disorder genes, SLC6A1, which encodes a γ-aminobutyric acid transporter, was associated with missense-damaging DNVs. In 1,122 trios for which genome-wide common variant data were available, schizophrenia and bipolar disorder polygenic risk were significantly overtransmitted to probands. Probands carrying LoF or deletion DNVs in LoF-intolerant or neurodevelopmental disorder genes had significantly less overtransmission of schizophrenia polygenic risk than did non-carriers, which provides a second robust line of evidence that these DNVs increase liability to schizophrenia

Targeted Sequencing of 10,198 Samples Confirms Abnormalities in Neuronal Activity and Implicates Voltage-Gated Sodium Channels in Schizophrenia Pathogenesis

Background Sequencing studies have pointed to the involvement in schizophrenia of rare coding variants in neuronally expressed genes, including activity-regulated cytoskeleton-associated protein (ARC) and N-methyl-D-aspartate receptor (NMDAR) complexes; however, larger samples are required to reveal novel genes and specific biological mechanisms. Methods We sequenced 187 genes, selected for prior evidence of association with schizophrenia, in a new dataset of 5207 cases and 4991 controls. Included among these genes were members of ARC and NMDAR postsynaptic protein complexes, as well as voltag

Contribution of copy number variants to schizophrenia from a genome-wide study of 41,321 subjects

Copy number variants (CNVs) have been strongly implicated in the genetic etiology of schizophrenia (SCZ). However, genome-wide investigation of the contribution of CNV to risk has been hampered by limited sample sizes. We sought to address this obstacle by applying a centralized analysis pipeline to a SCZ cohort of 21,094 cases and 20,227 controls. A global enrichment of CNV burden was observed in cases (OR=1.11, P=5.7×10−15), which persisted after excluding loci implicated in previous studies (OR=1.07, P=1.7 ×10−6). CNV burden was enriched for genes associated with synaptic function (OR = 1.68, P = 2.8 ×10−11) and neurobehavioral phenotypes in mouse (OR = 1.18, P= 7.3 ×10−5). Genome-wide significant evidence was obtained for eight loci, including 1q21.1, 2p16.3 (NRXN1), 3q29, 7q11.2, 15q13.3, distal 16p11.2, proximal 16p11.2 and 22q11.2. Suggestive support was found for eight additional candidate susceptibility and protective loci, which consisted predominantly of CNVs mediated by non-allelic homologous recombination