#Pseudogenes that might have saved us!
http://www.sciencedaily.com/releases/2012/06/120604155554.htm?fb_ref=.T829TjfxGmI.like&fb_source=home_oneline Interesting link to infectious disease for pseudo-siglecs 13 & 17
“”In a small, restricted population, a single mutation can have a big effect, a rare allele can get to high frequency,” said senior author Ajit Varki, MD, professor of medicine and cellular and molecular medicine and co-director of the Center for Academic Research and Training in Anthropogeny at UC San Diego. “We’ve found two genes that are non-functional in humans, but not in related primates, which could have been targets for bacterial pathogens particularly lethal to newborns and infants. Killing the very young can have a major impact upon reproductive fitness. Species survival can then depend upon either resisting the pathogen or on eliminating the target proteins it uses to gain the upper hand.”
In this case, Varki, who is also director of the UC San Diego Glycobiology Research and Training Center, and colleagues in the United States, Japan and Italy, propose that the latter occurred. Specifically, they point to inactivation of two sialic acid-recognized signaling receptors (siglecs) that modulate immune responses and are part of a larger family of genes believed to have been very active in human evolution.
Working with Victor Nizet, MD, professor of pediatrics and pharmacy, Varki’s group had previously shown that some pathogens can exploit siglecs to alter the host immune responses in favor of the microbe. In the latest study, the scientists found that the gene for Siglec-13 was no longer part of the modern human genome, though it remains intact and functional in chimpanzees, our closest evolutionary cousins. The other siglec gene — for Siglec-17 — was still expressed in humans, but it had been slightly tweaked to make a short, inactive protein of no use to invasive pathogens.”