New insights into epigenetics as an influencer: An associative study between maternal prenatal factors in Autism Spectrum Disorder (ASD)

Patterns of DNA methylation and chromatin structure are profoundly altered in neoplasia and include genome-wide losses of, and regional gains in, DNA methylation. The recent explosion in our knowledge of how chromatin organization modulates gene transcription has further highlighted the importance of epigenetic mechanisms in the initiation and progression of human cancer. These epigenetic changes -- in particular, aberrant promoter hypermethylation that is associated with inappropriate gene silencing -- affect virtually every step in tumour progression. In this review, we discuss these epigenetic events and the molecular alterations that might cause them and/or underlie altered gene expression in cancer.

We examined whether metabolic conditions (MCs) during pregnancy (diabetes, hypertension, and obesity) are associated with autism spectrum disorder (ASD), developmental delays (DD), or impairments in specific domains of development in the offspring. Children aged 2 to 5 years (517 ASD, 172 DD, and 315 controls) were enrolled in the CHARGE (Childhood Autism Risks from Genetics and the Environment) study, a population-based, case-control investigation between January 2003 and June 2010. Eligible children were born in California, had parents who spoke English or Spanish, and were living with a biological parent in selected regions of California. Children's diagnoses were confirmed by using standardized assessments. Information regarding maternal conditions was ascertained from medical records or structured interview with the mother. All MCs were more prevalent among case mothers compared with controls. Collectively, these conditions were associated with a higher likelihood of ASD and DD relative to controls (odds ratio: 1.61 [95% confidence interval: 1.10-2.37; odds ratio: 2.35 [95% confidence interval: 1.43-3.88], respectively). Among ASD cases, children of women with diabetes had Mullen Scales of Early Learning (MSEL) expressive language scores 0.4 SD lower than children of mothers without MCs (P < .01). Among children without ASD, those exposed to any MC scored lower on all MSEL and Vineland Adaptive Behavior Scales (VABS) subscales and composites by at least 0.4 SD (P < .01 for each subscale/composite). Maternal MCs may be broadly associated with neurodevelopmental problems in children. With obesity rising steadily, these results appear to raise serious public health concerns.

DNA methylation, an essential epigenetic feature of DNA that modulates gene expression and genomic integrity, is catalyzed by methyltransferases that use the universal methyl donor S-adenosyl-l-methionine. Methylenetetrahydrofolate reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate (5-methylTHF), the methyl donor for synthesis of methionine from homocysteine and precursor of S-adenosyl-l-methionine. In the present study we sought to determine the effect of folate status on genomic DNA methylation with an emphasis on the interaction with the common C677T mutation in the MTHFR gene. A liquid chromatography/MS method for the analysis of nucleotide bases was used to assess genomic DNA methylation in peripheral blood mononuclear cell DNA from 105 subjects homozygous for this mutation (T/T) and 187 homozygous for the wild-type (C/C) MTHFR genotype. The results show that genomic DNA methylation directly correlates with folate status and inversely with plasma homocysteine (tHcy) levels (P < 0.01). T/T genotypes had a diminished level of DNA methylation compared with those with the C/C wild-type (32.23 vs.62.24 ng 5-methylcytosine/microg DNA, P < 0.0001). When analyzed according to folate status, however, only the T/T subjects with low levels of folate accounted for the diminished DNA methylation (P < 0.0001). Moreover, in T/T subjects DNA methylation status correlated with the methylated proportion of red blood cell folate and was inversely related to the formylated proportion of red blood cell folates (P < 0.03) that is known to be solely represented in those individuals. These results indicate that the MTHFR C677T polymorphism influences DNA methylation status through an interaction with folate status.