Evidence for linkage on chromosome 3q25-27 in a large autism extended pedigree

Though autism shows strong evidence for genetic etiology, specific genes have not yet been found. We tested for linkage in a candidate region on chromosome 3q25 27 first identified in Finnish autism families [ 1]. The peak in this previous study was at D3S3037 ( 183.9 cM). We tested this region in seven affected family members and 24 of their relatives from a single large extended Utah pedigree of Northern European ancestry. A total of 70 single nucleotide polymorphisms ( SNPs) were analyzed from 165 to 204 cM. The maximum NPL-all nonparametric score using SimWalk2snp was 3.53 ( empirical p value = 0.0003) at 185.2 cM ( SNP rs1402229), close to the Finnish peak. A secondary analysis using MCLINK supported this result, with a maximum of 3.92 at 184.6 cM ( SNP rs1362645). We tested for alterations in a candidate gene in this region, the fragile X autosomal homolog, FXR1. No variants likely to contribute to autism were found in the coding sequence, exon-intron boundaries, or the promoter region of this gene.