AUTISM AND THE SEROTONIN TRANSPORTER GENE
The role of the serotonin transporter (5-HTT) in the development of neuropsychiatric disorders has been widely investigated. A genetic research shed new light on its role (Conroy et al. Serotonin transporter gene and autism: a haplotype analysis in an Irish autistic population. Molecular Psychiatry 9, 587-593, June 2004). Two polymorphisms, an insertion-deletion in the promoter region and a 12 repeat allele in a variable nucleotide tandem repeat (VNTR) in intron 2, drive higher expression of the 5-HTT gene. Four studies have shown nominally significant excess transmission of alleles of the 5-HTT gene in autism, while three studies have reported no excess transmission. Conroy’s study investigates the role of 5-HTT in the genetically homogenous Irish population. In all, 84 families were genotyped for five polymorphisms.
The most significant haplotype associated with transmission to affected probands was the SNP10VNTRSNP18 haplotype. This haplotype included the 12 repeat allele of the VNTR, which is associated with increased expression and may play a subtle role in the early development of the brain in affected probands.