A new study published in Journal of Biological Chemistry aimed to investigate the assembly of a protein molecule that helps the immune system identify threats and invaders. What initially sounds like quite a specialist biology/chemistry topic turned out to be of wider evolutionary relevance since they concluded that the receptor might have been inherited from local Neanderthal populations.
The human leukocyte antigen (HLA) system scans cells to identify if they are a threat to the body or not, and helps to protect from local diseases. A collaborative team recently discovered a fourth receptor that can perform this task and investigated how the gene sequences that control this receptor are assembled. They compared this gene sequence with several databases, including the recently mapped Neanderthal genome, and came to some interesting conclusions.
The study found that the K69/GGPM84-87 motif, which is essential for the formation of this receptor, is present in both Neanderthals and modern humans. Moreover, the DPB1*0401 allele which contains the K/GGPM motif is present only in 11 % of Sub-Saharan African populations whereas 68 % of the European population carry this allele. Recently, it was already discovered that some HLA class I alleles in the European population were from ancient origin and presumably transmitted by resident Neanderthals to immigrating humans and this study gives further weight to this idea.
The findings suggest that a Neanderthal gene was introduced into the Homo sapiens genome by admixture of the two human species. It is assumed that the resident Neanderthals had immune systems adapted to local pathogens in Europe. This HLA class II peptide receptor may have then evolved further in ancient Homo sapiens to a novel DP family in modern humans. If this interpretation is substantiated it may indicate that the adoption of this Neanderthal allele provided a selective advantage to these early modern human populations.
Reference: Sebastian Temme, Martin Zacharias, Jürgen Neumann, Sebastian Wohlfromm, Angelika König, Nadine Temme, Sebastian Springer, John Trowsdale and Norbert Koch. A novel family of human lymphocyte antigen class II receptors may have its origin in archaic human species, Journal of Biological Chemistry, DOI: 10.1074/jbc.M113.515767