Investigation of two variants in the DOPA decarboxylase gene in patients with autism.

Though genetic risk factors are important for the development of autism, no specific risk alleles have yet been identified. DOPA decarboxylase (DDC) is involved in both the catecholaminergic and serotonergic pathways and may be considered a functional candidate gene for autism. The present study is the first to test if two new variants of possible functional significance in the DDC gene increase the susceptibility to autism. A total of 90 parent-offspring trios recruited in Denmark and France were investigated using the transmission disequilibrium test (TDT). We found no evidence of linkage disequilibrium between autism and either of the two polymorphisms. Nor did we find linkage disequilibrium between autism and haplotypes of the two variants using a multiallelic TDT. These findings suggest that the DDC gene is unlikely to play a major role in the development of autism in our data set.