It is estimated that 9 percent of the human genome of is viral origin. For decades scientists have thought that this genetic material is useless junk DNA. However, recent research has demonstrated many of these sequences are not always inactive. One of these so-called “endogenous retroviruses,” called HERVK, is seemingly expressed in human embryos. Importantly, HERVK appears to play critical roles in viral defense and early development.
Discussing what this appears to mean, Joanna Wysocka of Stanford University told New Scientist of the three-day-old embryos she and her colleagues investigated. Wysocka said: “The cells were full of viral [HERVK] protein products, some of which had assembled to form viral-like particles.”
The initial studies suggest that the viral products included a protein that prevented other viruses, such as influenza, from penetrating the embryo and coordinated the translation of certain host RNAs.
It would seem HERVK took up residence in the human genome just 200,000 years ago. Such viruses are present very early on in the embryo, and could be involved in some critical developmental programs. This finding could herald an exciting area of viral research.
The findings have been published in the science journal Nature. The study is titled “Intrinsic retroviral reactivation in human preimplantation embryos and pluripotent cells.”
