Epigenetic Interface of Autism Spectrum Disorders (ASDs): Implications of Chromosome 15q11-q13 Segment

Autism spectrum disorders (ASDs) are multifactorial in nature and include both genetic and environmental factors. The increasing evidence advocates an important role of epigenetics in ASD etiology. One of the most common forms of epigenetic changes observed in the case of neurodevelopmental disorders is imprinting which is tightly regulated by developmental and tissue-specific mechanisms. Interestingly, many of these disorders that demonstrate autism-like phenotypes at varying degrees have found involvement of chromosome 15q11-q13 segment. Numerous studies demonstrate occurrence of ASD in the presence of chromosomal abnormalities located mainly in Chr15q11-q13 region. Several plausible candidate genes associated with ASD are in this chromosomal segment, including gamma aminobutyric acid A (GABA_A) receptor genes GABRB3, GABRA5 and GABRG3, UBE3A, ATP 10A, MKRN3, ZNF, MAGEL2, Necdin (NDN), and SNRPN. The main objective of this review is to highlight the contribution of epigenetic modulations in chromosome 15q11-q13 segment toward the genetic etiology and pathophysiology of ASD. The present review reports the abnormalities in epigenetic regulation on genes and genomic regions located on chromosome 15 in relation to either syndromic (15q11-q13 maternal duplication) or nonsyndromic forms of ASD. Furthermore, studies reviewed in this article demonstrate conditions in which epigenetic dysregulation has been found to be a pathological factor for ASD development, thereby supporting a role for epigenetics in the multifactorial etiologies of ASD. Also, on the basis of the evidence found so far, we strongly emphasize the need to develop future therapeutic strategies as well as screening procedures for ASD that target mechanisms involving genes located on the chromosomal 15q11-q13 segment.