Autistic Phenotype of Permutation and Intermediate Alleles of FMR1 Gene

Mutations in gene are the most common single genetic cause of autism-spectrum disorders, therefore we investigated the possibility that the intermediate alleles may also contribute to the origin of Autistic disorder.
We screened 96 males, recruited from North West of Iran, who were diagnosed with autistic disease for CGG repeat size. The frequencies of either intermediate or premutation alleles were matched with 168 male controls. All patients and normal controls were of Azeri Turkish ethnicity.
Three mutated, five intermediate and four premutation carriers were identified among Autistic patients, compared with one premutation carrier in normal controls, representing a significant excess in small size FMR1 allele carriers (= 0.006). There was also a significant excess of the intermediate carriers compared with normal controls (= 0.006).
Both of these alleles may show roles in the etiology of autism, possibly as a result of the rise of mRNA. Considering that there are individuals in the general population are carriers of intermediate and premutation alleles, further screening of larger samples of Autism patients is recommended, in order to estimate the role of small size of CGG repeat alleles in the aetiology of autism.