Objectives: To replicate previous findings using South Carolina and Italian autism cohorts.
Methods: Analyses were performed using samples from 270 autism patients and 460 controls. Fifty-six patients with autism spectrum disorder (ASD) were from Italy and 162 patients with classical autism were from the South Carolina Autism Project (Schroer et al. 1998 Am J Med Genet). Control samples consisted of 91 individuals from Italy and 369 from South Carolina. The rs1858830 variant was genotyped by PCR amplification and Eag I digestion. Fragments were separated and scored using agarose gel electrophoresis.
Results: Italian and South Carolina patient and control populations were found to be in Hardy-Weinberg equilibrium. In the Italian cohort, no significant association with ASD was found when comparing the CC to the GG genotype (odds ratio = 1.12; 95% CI = 0.47-2.67). Chi-square tests similar to those performed by Campbell et al. were not found to be significant.
In the South Carolina cohort, a significant association with classical autism was found when comparing the CC to the GG genotype (odds ratio = 1.89; 95% CI = 1.08-3.31). This association was also significant for cases from simplex families (odds ratio = 2.03; 95% CI = 1.14-3.61). Chi-square tests similar to those performed by Campbell et al. were found to be significant.
Conclusions: The rs1858830 variant was not found to be associated with ASD in an Italian cohort. However, this variant was found to be associated with classical autism in a South Carolina cohort. Since Campbell et al. found a stronger association in families with narrowly defined autism, these results imply that the MET promoter variant is more strongly associated with classical autism than ASD.