Our Neanderthal genes are active

Alleles inherited from the Ice Age cousin influence the activity of modern gene variants

We Europeans carry genes from the Neanderthals in us. © Thinkstock, AquilaGib / CC-by-sa 3.0
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Active Heritage: The Neanderthal genes in us are still active today - and even measurably influence the expression of modern genes, a study reveals. If there is a gene in our genome of a Neanderthal and a modern variant, then depending on the tissue and gene, sometimes the other one read more strongly. Striking: The brain and testes are dominated by the modern alleles almost throughout, as the researchers report in the journal "Cell".

Even if the Neanderthal extinct about 40, 000 years ago, a part of him lives on in us. Because on their way to Europe, some Homo sapiens crossed with the ice age people and begat hybrids. We Europeans therefore carry around two percent of Neanderthal DNA in us - and this to our advantage:

The genes inherited from our prehistoric cousin help us lose weight, strengthen our immune system and give our fair skin - theoretically. But whether these Neanderthal genes are ever active in our genome, was previously unknown.

An allele of Neanderthal man, one of modern man

To find this out, Rajiv McCoy of the University of Washington and his colleagues first sought in a global database of gene expression for participants who have a Neanderthal allele and a Homo sapiens allele of any gene. Each human received one version of each gene from the father and one from the mother.

For their study, the researchers then tested how much each of these two alleles in different body tissues is read. This is recognizable by the amount of RNA produced by these gene segments. The more active the allele, the more RNA is produced and the more blueprints for the corresponding protein the cell can then implement. display

This is how the Neanderthal alleles in our genome Cell

Influence each other

The result: "Even 50, 000 years after the last mating of Neanderthals and humans, we can still detect measurable effects on gene expression, " says co-author Joshua Akey of the University of Washington. The Neanderthal alleles are not only still active today, they also influence how strongly certain modern genes and gene variants are read from us.

As the researchers found, there are striking differences in which of the two alleles is more active. "At about 25 percent of the loci we tested, we can see a difference in gene expression between both alleles, " says McCoy. In some genes, the Neanderthal variant was more active, including in a gene for the immune messenger interleukin-18. In other cases, modern gene copy inhibited the activity of the Neanderthal allele.

Brain and testicles as extremes

Particularly striking was the discrepancy in the cells of the brain and in the male testicular tissue. "The extent to which the Neanderthal alleles in the brain were down-regulated is amazing, " say McCoy and his colleagues. Especially in the cerebellum and the basal ganglia, the gene variant inherited from our ice age cousin is very effectively suppressed. This could explain why, for example, the cerebellum is significantly larger in Homo sapiens than in the Neanderthal.

In testicular tissue, inhibition of Neanderthal alleles involved, among other things, genes important for sperm motility. It was also striking that all genes that are particularly active in the testes, no longer have Neanderthal variants, as the scientists report.

On the one hand, this confirms the recent discovery of extensive deletion of Neanderthal genes from our genetic material in the course of our further development. At the same time, the particular impoverishment of Neanderthal relics in the testes may indicate that male descendants of a cross between both human species may have been infertile.

Proud to this day

"The crossing of Neanderthals and modern humans was not just something that happened fifty thousand years ago and that is none of our business today, " says Akey. "Instead, the gene clippings of our Neanderthal heritage still influence our gene expression in a meaningful and important way today."

The genes inherited from our extinct cousin did not just help in the past to make us what we are today. They still affect our biology now. (Cell, 2017; doi: 10.1016 / j.cell.2017.01.038)

(Cell Press, 24.02.2017 - NPO)