A group of geneticists from Berkeley Lab, UC Davis, UC Santa Cruz, and UC Berkeley are unraveling new details about human evolution by studying the uniquely regulated portion of our chromosomes that surround the centromeres. These stretches of DNA – termed centromere-proximal regions (CPRs) – are largely composed of highly repetitive, mostly non-gene-coding sequences that are protected from sequence shuffling during reproductive cell division.
Hypothesizing that these protected genomic regions might generate large haplotypes (groups of neighboring genes and sequences that are inherited as a single unit from generation to generation), Berkeley Lab researcher Sasha Langley and her co-authors used a database of diverse modern human genomes to investigate variation in CPRs. Their analysis, published in eLife, revealed that centromere haplotypes – or “cenhaps” – are indeed present. Like other parts of the genome, cenhaps harbor genetic material, including functional genes, that were introduced when our ancestors hybridized with other hominin species; yet these sequences are surprisingly massive compared with other archaic genetic remnants.
“Interestingly, one of the Neanderthal cenhaps contains a lot of unique variation in genes that shape our sense of smell,” said Langley. “And in some individuals, we found evidence of an even more ancient cenhap that appears to be derived from a previously unknown early hominin relative.”
The authors conclude that cenhaps provide a great tool for exploring the history of early hominins, even when available fossils contain limited intact DNA.