Partitioning the heritability of Tourette syndrome and obsessive compulsive disorder reveals differences in genetic architecture.

The direct estimation of heritability from genome-wide common variant data as implemented in the program Genome-wide Complex Trait Analysis (GCTA) has provided a means to quantify heritability attributable to all interrogated variants. We have quantified the variance in liability to disease explained by all SNPs for two phenotypically-related neurobehavioral disorders, obsessive-compulsive disorder (OCD) and Tourette Syndrome (TS), using GCTA. Our analysis yielded a heritability point estimate of 0.58 (se = 0.09, p = 5.64e-12) for TS, and 0.37 (se = 0.07, p = 1.5e-07) for OCD. In addition, we conducted multiple genomic partitioning analyses to identify genomic elements that concentrate this heritability. We examined genomic architectures of TS and OCD by chromosome, MAF bin, and functional annotations. In addition, we assessed heritability for early onset and adult onset OCD. Among other notable results, we found that SNPs with a minor allele frequency of less than 5% accounted for 21% of the TS heritability and 0% of the OCD heritability. Additionally, we identified a significant contribution to TS and OCD heritability by variants significantly associated with gene expression in two regions of the brain (parietal cortex and cerebellum) for which we had available expression quantitative trait loci (eQTLs). Finally we analyzed the genetic correlation between TS and OCD, revealing a genetic correlation of 0.41 (se = 0.15, p = 0.002). These results are very close to previous heritability estimates for TS and OCD based on twin and family studies, suggesting that very little, if any, heritability is truly missing (i.e., unassayed) from TS and OCD GWAS studies of common variation. The results also indicate that there is some genetic overlap between these two phenotypically-related neuropsychiatric disorders, but suggest that the two disorders have distinct genetic architectures.

Cross-disorder genome-wide analyses suggest a complex genetic relationship between Tourette's syndrome and OCD.

OBJECTIVE: Obsessive-compulsive disorder (OCD) and Tourette's syndrome are highly heritable neurodevelopmental disorders that are thought to share genetic risk factors. However, the identification of definitive susceptibility genes for these etiologically complex disorders remains elusive. The authors report a combined genome-wide association study (GWAS) of Tourette's syndrome and OCD. METHOD: The authors conducted a GWAS in 2,723 cases (1,310 with OCD, 834 with Tourette's syndrome, 579 with OCD plus Tourette's syndrome/chronic tics), 5,667 ancestry-matched controls, and 290 OCD parent-child trios. GWAS summary statistics were examined for enrichment of functional variants associated with gene expression levels in brain regions. Polygenic score analyses were conducted to investigate the genetic architecture within and across the two disorders. RESULTS: Although no individual single-nucleotide polymorphisms (SNPs) achieved genome-wide significance, the GWAS signals were enriched for SNPs strongly associated with variations in brain gene expression levels (expression quantitative loci, or eQTLs), suggesting the presence of true functional variants that contribute to risk of these disorders. Polygenic score analyses identified a significant polygenic component for OCD (p=2×10(-4)), predicting 3.2% of the phenotypic variance in an independent data set. In contrast, Tourette's syndrome had a smaller, nonsignificant polygenic component, predicting only 0.6% of the phenotypic variance (p=0.06). No significant polygenic signal was detected across the two disorders, although the sample is likely underpowered to detect a modest shared signal. Furthermore, the OCD polygenic signal was significantly attenuated when cases with both OCD and co-occurring Tourette's syndrome/chronic tics were included in the analysis (p=0.01). CONCLUSIONS: Previous work has shown that Tourette's syndrome and OCD have some degree of shared genetic variation. However, the data from this study suggest that there are also distinct components to the genetic architectures of these two disorders. Furthermore, OCD with co-occurring Tourette's syndrome/chronic tics may have different underlying genetic susceptibility compared with OCD alone.

[Association of Schizophrenia and its Clinical Implications with the NOS1AP Gene in the Colombian Population]. / Asociación de esquizofrenia y sus dimensiones clínicas con el gen NOS1AP en población colombiana.

INTRODUCTION: The nitric oxide synthase 1 adaptor protein (NOS1AP) gene is possibly implicated in schizophrenia etiopathogenesis. OBJECTIVE: To determine the association of NOS1AP gene variants with schizophrenia and the relationship of variants with the clinical dimensions of the disorder in the Colombian population. METHODOLOGY: It is a case-control study with 255 subjects per group. Markers within the NOS1AP gene were typified as well as other informative material of genetic origin so as to adjust by population stratification. A factorial analysis of the main components for each item in the Scales for Evaluating Negative Symptoms (SENS) together with the Scales for Evaluating Positive Symptoms (SEPS) to determine clinical dimensions. RESULTS: Association between the C/C genotype of the rs945713 marker with schizophrenia (OR = 1.79, 95% CI: 1.13 - 2.84) was found. The C/C genotype of the rs945713 was related to higher scores in the "affective flattening and alogia" dimension; and the A/A genotype of the rs4657181 marker was associated to lower scores in the same dimension. CONCLUSIONS: Significant associations of markers inside the NOS1AP gene with schizophrenia and the "affective flattening and alogia" clinical dimension were found. These results are consistent with previous studies and support the possibility that NOS1AP influences schizophrenia susceptibility. Furthermore, NOS1AP might be a modifier of schizophrenia clinical characteristics.

Exploring epistasis in candidate genes for antisocial personality disorder.

OBJECTIVE: To identify and characterize high-order gene-to-gene interactions in antisocial personality disorder (ASPD). METHODS: Participants for case-control study were selected from the inmate male population in Bellavista prison from Medellin. The study included 310 individuals with ASPD and 200 with no ASPD. Diagnoses were made according to a best-estimate procedure based on a semistructured interview (diagnostic interview for genetic studies 3.0). We genotyped some single-nucleotide polymorphisms in candidate genes with main serotonin pathway effects. The gene-gene interaction was examined using the multifactor dimensionality reduction method version 2.0.α. We assessed model sizes of 2 and 3 loci and counted the number of replicates that contained the causal loci in the final best model that was identified using 10-fold cross validation. RESULTS: We find epistatic interaction with catechol-O-methyl transferase (COMT), tryptophan hydroxylase, and 5-HTR2A (serotonin receptor) with ASPD. This data supports an important role of polymorphism in serotonin receptors and low enzyme activity of COMT for susceptibility to ASPD. CONCLUSION: This study suggests that gene interactions between genetic variants in COMT, 5-HTR2A and tryptophan hydroxylase gene would be associated with ASPD and influence the dopamine rewards pathways and modulate serotonin levels in ASPD.

An approach to the etiology of metabolic syndrome / Un acercamiento a la etiología del síndrome metabólico

Increased prevalence of obesity in the world, especially ac-cumulation of abnormal amounts of visceral fat predisposesto insulin resistance, which is the central role of metabo-lic syndrome (MS). Obesity can deregulate the intracellularsignaling of insulin due to the production of inflammatorysubstances, chemoattractant proteins, adipokines and mo-lecules that trigger hormonal mediator potentials for des-tabilization of signal transduction, leading to metabolicdisorders such as hyperglycemia, hypertension, and dyslipi-demia. The complexity of the MS and of the genetic mecha-nisms involved in its etiology derives from the combinationof variants on genes involved and environmental factorsthat predispose it. The purpose of this paper is to review theeffects of obesity in molecular and biochemical responsesthat trigger insulin resistance and its relation to some candi-date genes and the ancestral component of the population.

Asociación de esquizofrenia y sus dimensiones clínicas con el gen NOS1AP en población colombiana / Association of schizophrenia and its clinical implications with the nos1ap gene in the colombian population

Introducción: El gen NOS1AP codifica para la proteína adaptadora de óxido nítrico sintasa neuronal 1, que posiblemente está implicada en la etiopatogénesis de la esquizofrenia. Objetivos: Determinar si existe asociación de variantes en el gen NOS1AP con esquizofrenia y si estas variantes tienen relación con las dimensiones clínicas del trastorno en población colombiana. Metodología: Es un estudio de casos y controles, con 255 sujetos por grupo. Se tipificaron marcadores dentro del gen NOS1AP y otros informativos de origen genético, con el fin de ajustar por estratificación de la población. Se hizo un análisis factorial de componentes principales de cada uno de los ítems de las escalas de evaluación de síntomas negativos (SANS) y de síntomas positivos (SAPS) para determinar las dimensiones clínicas. Posteriormente, se evaluó la asociación de las variantes genéticas con la esquizofrenia y con cada una de las dimensiones. Resultados: Se encontró asociación entre el genotipo C/C del marcador rs945713 con esquizofrenia (OR = 1,79, IC95%: 1,13-2,84). El genotipo C/C de rs945713 se asoció con puntuaciones más altas en la dimensión “aplanamiento afectivo y alogia” y el genotipo A/A del marcador rs4657181 se relacionó con puntuaciones más bajas en esa misma dimensión. Conclusiones: Se encontró asociación significativa de marcadores dentro de NOS1AP con esquizofrenia y la dimensión clínica “aplanamiento afectivo y alogia”. Estos resultados son consistentes con estudios previos y apoyan la posibilidad de que NOS1AP influya en la susceptibilidad a esquizofrenia y que sea un modificador de sus características clínicas…

Introduction: The nitric oxide synthase 1 adaptor protein (NOS1AP) gene is possibly implicated in schizophrenia etiopathogenesis. Objective: To determine the association of NOS1AP gene variants with schizophrenia and the relationship of variants with the clinical dimensions of the disorder in the Colombian population. Methodology: It is a case-control study with 255 subjects per group. Markers within the NOS1AP gene were typified as well as other informative material of genetic origin so as to adjust by population stratification. A factorial analysis of the main components for each item in the Scales for Evaluating Negative Symptoms (SENS) together with the Scales for Evaluating Positive Symptoms (SEPS) to determine clinical dimensions. Results: Association between the C/C genotype of the rs945713 marker with schizophrenia (OR = 1.79, 95% CI: 1.13 – 2.84) was found. The C/C genotype of the rs945713 was related to higher scores in the “affective flattening and alogia” dimension; and the A/A genotype of the rs4657181 marker was associated to lower scores in the same dimension. Conclusions: Significant associations of markers inside the NOS1AP gene with schizophrenia and the “affective flattening and alogia” clinical dimension were found. These results are consistent with previous studies and support the possibility that NOS1AP influences schizophrenia susceptibility. Furthermore, NOS1AP might be a modifier of schizophrenia clinical characteristics…

Amplificación de ADN a partir de un molde unido a membrana / DNA amplification from a mold together with membrane

con el fin de mantener muestras de ácido desoxirribonucleico (ADN) para amplificaciones sucesivas por PCR a partir de muestras de limitada disponibilidad debido a la dificultad para su obtención o extracción, y además poder ser almacenadas en pequeños espacios, se estandarizó una técnica para amplificaciones por reacción en cadena de la polimerasa (PCR) usando como molde una cadena de ADN (ssDNA) unido a una membrana. Tres tipos de membranas (de nylon con carga positiva y sin carga, de nitrocelulosa y Zeta-Probe) y tres métodos de fijación (alcalino, luz ultravioleta y calor) fueron usados para amplificar tres loci humanos, tomando tres concentraciones de ADN para cada uno de ellos. Los mejores resultados fueron obtenidos cuando se usó la membrana de nylon sin carga, fijación con calor o luz UV, y el tamaño del amplificado estuvo por debajo de 500 pb y la concentración del ADN unida a la membrana fue mayor de 0,115 mgmL