These Little Piggies!
23 November 2009: 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.
In the recent issue of Biology of Reproduction (Bischoff et al. 2009), the most comprehensive analysis of imprinted genes in pigs to date was published. In addition to identifying 25 imprinted genes, this study showed that the pattern of genes imprinted in pigs is more similar to that in humans than in mice. Thus, pigs may be a better model than mice for human developmental disorders and diseases that result primarily from the epigenetic deregulation of imprinted genes. Or Maybe, The proper study of mankind is man., as was so prophetically stated by the English poet Alexander Pope in the early 18th century.