Epigenetic modification of DNA, mostly methylation, is the way which ensures lineage specity in mammalian organization and propagation of cell types. It is inherited while cells multiply.
In Nature this week (doi:10.1038/nature13648) Reik and Kelsey describe two article (et al. Nature 511, 606–610 (2014) and et al. Nature 511, 611–615 (2014)) where the methylation patterns in egg, sperm, fertilized eggs and blastocysts are analyzed. As has been found in mice before, blastocysts lose most of their methylation. Later in development the DNA gets remethylated again. This has been suggested but formal proof was lacking. The imprinting – methylated gene regions due to maternal or paternal origin – is not as much removed for maternal genes, but for paternal ones.
Whether these papers will improve human stem cell research is to be seen.
Two reviews in Trends in Endocrinology and Metabolism (DOI: http://dx.doi.org/10.1016/j.tem.2014.05.001 and DOI: http://dx.doi.org/10.1016/j.tem.2014.03.013) address the development and the pathogenesis of pancreatic β-cells. Conrad, Stein and Hunter describe the transcription factors in mice and man which lead to β-cell genesis while Thomsem and Gloyn focus their attention to malfunction leading diabetes mellitus. Both reviews together show the actual status in β-cell research.
There is an very interesting paper in Nature (doi:10.1038/nature12961) about the Neanderthal genom part in modern men. It shows an a chromosome by chromosome demonstration how much of the Neanderthal ancestry is found in the autosomes and in the sex chromosome: about 1 % in autosome and considerable less in sex chromomes. In the Y-chromosome it is barely found.
When the two populations first encounterd some 50000 years ago (as a paper form PLOS suggested: DOI: 10.1371/journal.pgen.1002947) we can envisage how this was done: there was war and the Neanderthal female were raped after the man were killed. Whether this was a singular event or repeatingly done in the clash of general war betweem the two species is not documented, but when the progeny e.g. was selected for the “African” phenotyp then the Neatherthal would be not maintained in the Y chromosome.
Very suggestive! And much has not changed till modern times