Around two to five percent of modern European DNA contains Neanderthal genes, thought to be the result of humans-Neanderthal interbreeding some 50,000 years ago. Now scientists at the University of Washington have found evidence that this Neanderthal DNA affects genetic expression related to certain traits and disease susceptibility.
'Hybridisation wasn't just something that happened 50,000 years ago that we don't have to worry about anymore,' said Joshua Akey of the University of Washington, who led the study, to the IB Times. 'Those little bits and pieces, our Neanderthal relics, are influencing gene expression in pervasive and important ways.'
The Neanderthal genome was mapped in 2008. Previous studies have found links between Neanderthal genes and certain traits, yet working out how these genes functioned compared to modern human counterparts has been challenging.
The scientists used data from the Genotype Tissue Expression Project, which indicates levels of gene activity in individual human tissues. They compared individuals with one human and one Neanderthal copy of any given gene to individuals with two human alleles of the same gene. They analysed differences in gene expression in 52 types of human tissue from 214 individuals of European heritage. Differences were found in a quarter of tissues.
The researchers say this shows Neanderthal genes still affect a diverse range of tissue functions in the body, including dictating which variants of protein are produced. For example Neanderthal DNA was shown to control one such gene, ADAMTSL3, in a way that would reduce the risk of schizophrenia and increase height.
Tissues showing the lowest levels of Neanderthal gene expression included the testes, and brain regions involved in fine motor control, perception and language processing.
'The finding that these Neanderthal variants tend to have lower activity in brains and testes is intriguing, as it offers hints on which aspects of biology diverged most rapidly between Neanderthals and us,' said Sriram Sankararaman of the University of California, who was not involved in the study.
The authors suggest that a loss of control by Neanderthal DNA over gamete formation coincided with the decline in human-Neanderthal interbreeding.
The group may next investigate whether interbreeding with other species of hominins has contributed to gene expression in modern humans. They say their technique could also be used to compare gene expression differences between modern human alleles.