Objective Autism Spectrum Disorder (ASD) is characterized by deficits in social function and the presence of repetitive and restrictive behaviors. by SRS respondent genome-wide significant linkage for social responsiveness was identified at chr8p21.3 (multi-point LOD=4.11; teacher/parent scores) and chr8q24.22 (multi-point LOD=4.54; parent-only scores) respectively. Genome-wide or linkage-directed association analyses did not detect common variants contributing to social responsiveness. Conclusions The sex-differential distributions of SRS in multiplex autism families likely reflect mechanisms contributing to the sex ratio for autism observed in the general population and form a quantitative signature of reduced penetrance of inherited liability to ASD among females. The identification of two strong loci for social responsiveness validates the endophenotype Epirubicin Hydrochloride approach for the identification of genetic variants contributing to complex traits such as ASD. While causal mutations have yet to be identified these findings are consistent with segregation of rare genetic variants influencing social responsiveness and underscore the increasingly recognized role of rare inherited variants in the genetic architecture of ASD. (2009) (22) and subjected to impartial quality filtering. Additional families were genotyped in the UCLA Neuroscience Genomics Core (UNGC http://www.semel.ucla.edu/ungc) around the Illumina Omni-1 Quad and Omni-2.5-8 platforms (Illumina San Diego CA) according to standard manufacturer protocols. Familial relationships in the combined data set were validated using identity-by-descent (IBD) estimation in PLINK (23). For any monozygotic (MZ) twin pairs or sample duplicates detected during relationship validation only one individual was retained for downstream analyses. Each data set was subjected to the following quality filters Epirubicin Hydrochloride Epirubicin Hydrochloride as applied in PLINK: �� 5% missing data per person or per SNP; minor allele frequency (MAF) �� 1%; Hardy-Weinberg Equilibrium (HWE) p �� 10?7. Because SRS scores were available for only a subset of the genotyped cohort analyses for SRS included 590 families with 1 480 phenotyped individuals. Genotype imputation was performed separately on each data set using IMPUTE2 and a cosmopolitan reference panel from the 1000 Genomes Project (24-26). Quality filters included: IMPUTE2 quality score (info) ��0.5; missing data per SNP �� 5%; MAF �� 1%; HWE p �� 10?7. The final data set included 5 814 564 autosomal SNPs passing quality filters. Linkage analyses An independent marker set (r2��0.1) was identified from the genotyped SNP sets using PLINK (option –indep-pairwise) (23). The pruned marker set consisted of 52 354 autosomal SNPs common to all genotyping platforms. Non-parametric multi-point analyses were performed in Merlin (27). Genome-wide multi-point LOD scores can be found in Supplemental Tables ST2 and ST3. Association analyses Single-SNP association analyses for SRS as a quantitative trait were performed on imputed genotypes using the –qfam-total option in PLINK (23) which applies linear regression and uses permutation to correct for non-independence between family members. Analyses for autism diagnosis as a qualitative trait were performed using the Rabbit Polyclonal to CKI-alpha1/L. –tdt option in PLINK with gene-dropping permutations to correct for non-independence between trios drawn from multiplex families. There were 2 236 affected offspring in 1 250 two-parent families analyzed for association including trios not used to conduct linkage. Bonferroni correction was applied to p-values derived from association analyses in the linked regions of interest using the number of impartial markers in the region as determined using the –indep-pairwise option in PLINK at r2��0.5. RESULTS Clinical/phenotype characteristics We identified families from the Autism Genetic Resource Exchange (AGRE) where two or more offspring had been assessed using the Social Responsiveness Scale (SRS) (11). To maximize the cohort of genotyped and phenotyped individuals we used a combination of teacher-reported and parent-reported SRS scores. The cohort consisted of 590 families including 1 480 phenotyped individuals (Table 1). We examined Epirubicin Hydrochloride total raw SRS scores in the offspring and observe a roughly bimodal distribution correlating with ASD diagnosis (Physique 1). Similarly there are more male offspring with high SRS scores (indicating greater social impairment) consistent with the male sex.