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'Hot off the press' is a daily listing of the most recent articles in epigenetics and imprinting

Autism and Schizophrenia: The Antithesis of Each Other?

24 November 2014: Genomic imprinting is a phenomenon where one parental allele is silenced epigenetically, resulting in monoallelic parent-of-origin gene expression (Jirtle and Weidman 2007). It evolved about 150 million years ago with the advent of viviparity and placentation in a common ancestor to Therian mammals (i.e. Marsupials and Eutherians) (Killian et al. 2000). Badcock and Crespi postulated in their imprinted brain theory that autism spectrum disorders (AS) and schizophrenia spectrum (SS) disorders are the antithesis of each other, and result from the skewing of paternally and maternally imprinted gene expression in the brain during development. Paternally expressed imprinted genes tend to be progrowth, and those that are maternally expressed antigrowth. This theory predicts that full term above average-sized babies would have a significantly higher risk of AS disorders concomitant with a significantly lower risk of SS disorders. In contrast, full term below average-sized babies would have a lower risk of AS, but a significantly greater risk for developing SS disorders. This unique opposite risk pattern for AS and SS disorders was indeed demonstrated to be associated with normal variation in birth size in a recent Danish study (Byars et al.) of 1.8 million babies of which 95 thousand had AS or SS. Now, to assess the role that imprinted gene dysregulation plays in the genesis of these neurological disorders, we need to identify the complete repertoire of human imprinted genes, and their regulatory elements, the imprintome (Skaar et al. ).

Environmental Epigenomics in Health and Disease

Springer has recently published two books on environmental epigenomics that are edited by Randy L. Jirtle and Frederick L. Tyson -- Epigenetics and Disease Origins and Epigenetics and Complex Diseases. The overall purpose of these books is to give readers an overview of how environmental exposures can influence the risk of disease in adulthood by disrupting epigenetic processes and reprogramming during early development. Read more...

Radiation Epigenetics

Humans are exposed to low-dose ionizing radiation (LDIR) from a number of environmental and medical sources. In addition to inducing genetic mutations, there is concern that LDIR may also alter the epigenome. Such heritable effects early in life can either be positively adaptive or result in the enhanced formation of diseases, including cancer, diabetes, and obesity. In this study, we show that LDIR significantly increases DNA methylation at the viable yellow agouti (Avy) locus in a dose- and sex-dependent manner. Moreover, maternal dietary antioxidant supplementation mitigated both the DNA methylation changes and coat color shift in the irradiated offspring. Thus, LDIR exposure during gestation elicits epigenetic alterations that lead to positive adaptive phenotypic changes that are negated with antioxidants, indicating they are mediated in part by oxidative stress. Read more...

These Little Piggies!

Imprinted genes are monnoallelically expressed in a parent-of-origin dependent manner because the same parental allele is always epigenetically silenced (Jirtle and Weidman 2007). The phenomenon of genomic imprinting evolved in mammals around 200 million years ago in a common ancestor to marsupials and eutherians (Killian et al. 2000). Once this unique epigenetic form of gene regulation evolved, natural selection may have utilized the resulting marked variation in gene expression to drive mammalian speciation, providing a plausible explanation for why mammalian species vary markedly in their imprinted gene repertoires. Read more...

Epigenetic Basis of Suicide Risk?

Not all multigenerational effects are transmitted through the germ line. Elegant studies in rats demonstrate that generation-to-generation attainment of the nurturing behaviors of pup licking and grooming and arch-back nursing are not germline inherited. Rather, they are passed on to the offspring directly from the mother during the first week of postnatal life through the induction of DNA methylation and histone alterations in the hippocampus (Weaver et al. 2004). Moreover, the inherent plasticity of the epigenome allows for the reversal of these modifications in adulthood by exposure to epigenetic therapeutic agents (Weaver et al. 2006). Read more...

Genome-wide Mapping of Human Imprinted Genes

Genomic imprinting is an epigenetic form of gene regulation that results in only the copy inherited from the mother or father to function (Jirtle and Weidman 2007). The phenomenon of imprinting evolved about 150 M years ago in a common ancester to mammals that have live birth - the Therian mammals (Marsupials and Eutherians) (Killian et al. 2000). Read more...