Objectives: To investigate the association between the GAD2 gene and cortical anatomy in ASD.
Methods: A sample of 64 individuals (42 clinically diagnosed ASD cases and 22 healthy controls) underwent a conventional SPGR scan; FreeSurfer software was used to automatically label 34 subdivisions of each hemisphere and calculate cortical volumes. Each subject was genotyped for 10 SNPs tagging the GAD2 gene using Taqman procedures. Haplo.Stats was used in conjunction with R Statistically Computing for haplotypic and statistical analysis.
Results: We found a significant decrease in cortical volume of ASD inferior parietal cortex (p = 0.0089). Haplo.Stats identified a significantly associated 3 marker haplotype with ASD cases. All possible haplotype combinations were identified and their frequencies calculated. Hap1 and Hap3 showed the highest frequencies and were examined further. Subjects expressing Hap3 showed a significant increase in inferior parietal cortical volume (0.00025), however a significant reduction was noted in ASD cases expressing Hap3 (0.0005) using generalized linear regression analysis.
Conclusions: Our work adds to post mortem evidence that Cortical volume reduction in the left inferior parietal cortex of the ASD brain may be related to haplotypes of the GAD2 gene.