Association Study Between Metallothionein-3 Protein Polymorphisms and Autism.

Genetic susceptibility to high mercury body burden has been suggested as an autism risk factor in children. Metallothionein III (MT3) is the brain-specific form of the metallothionein family, which plays a key role in metal metabolism. We therefore looked for genetic variations in the MT3 gene that might increase the predisposition to autism. DNA was extracted from 132 autistic children and 132 age and gender-matched unrelated controls. All the samples were analyzed for nine single nucleotide polymorphisms (SNPs) with minor allele frequency > 10% in the MT3 gene. The mRNA levels of MT3 in white blood cells were evaluated by real-time PCR. We did not detect any association between these MT3 polymorphisms and the mRNA levels of MT3. We did not detect any association between MT3 polymorphisms and autism risk. However, we detected four novel MT3 SNPs that are not in the human SNP database. The clinical importance of these SNPs needs further investigation. Our data suggest that MT3 gene polymorphisms are not associated with autism.