Polymorphism of Folate Cycle Genes and Severity of Autism Spectrum Disorders

The purpose of this work is to study the polymorphisms of folate cycle genes and the distribution
of polymorphic variants of genes depending on the severity of autism spectrum disorders. The
study included 102 patients with autism spectrum disorders aged from 2 to 10 years. Detection
of mutations in the folate cycle genes MTHFR C677T, MTHFR A1298C, MTRR A66G, MTR A2756G
was performed with molecular genetic analysis using the diagnostic kits "SNP-Screen" and "DNAExtran".
To quantify the severity of autism spectrum disorders, the Autism Diagnostic Observation
Schedule (ADOS-2) was used. As a result of the study, it was noted that the study group of children
in 98% of cases revealed polymorphism of the folate cycle genes. The frequency of distribution
of polymorphic variants prevailed in the MTRR A66G gene 78,4% (49% AG; 29,4% G/G) and in the
MTHFR C677T gene 66,6% (44% C/T; 22,5% T/T). In 22,5% of cases, there was a polymorphism in
the homozygous state of T/T, the gene MTHFR 677. The gene MTHFR A1298C polymorphism was
52 % (40% A/C; 12% C/C), and the gene MTR A2756G polymorphism was observed in 51% of cases
(35,2% A/G; 15.6% G/G). According to the ADOS-2 method, in 45 cases (44%), moderate severity
of autism symptoms was detected, in 34% of cases (35 children) – severe, in 22% of children, light
severity of clinical signs of autism was revealed. A statistically reliable distribution of heterozygous
and homozygous allelic variants of folate cycle genes was revealed depending on the severity of
autism spectrum disorders (p<0.05). Heterozygous polymorphisms of folate cycle genes are most often found in moderate severity of ASD, and the largest number of homozygous polymorphisms of folate cycle genes is distributed in severe clinical signs of autism.