The human Y chromosome has been shrinking. Over hundreds of millions of years, it has shed about 97 percent of its original genes. Could the loss of a few more genes tip it into extinction? Not according to HHMI Investigator David Page of the Whitehead Institute for Biomedical Research. He believes that the jettisoning of genes has stopped.
In an April 24, 2014, Nature paper, Page and his colleagues compared the sequences of Y chromosomes from eight mammals, including humans, to reconstruct that chromosome’s evolution. Their results showed that, although there was a period of rapid degeneration and gene loss during the early days of its evolution, the Y chromosome retained a subset of ancestral genes that have remained remarkably stable for the past 25 million years.
Moreover, the nature of the surviving genes hints that a Y chromosome may do more than just dictate the gender of its owner. Most of the genes have little to do with sex determination or sperm production. Instead, they play roles in protein synthesis, RNA splicing, and gene regulation. What’s more, they are expressed in the heart, lungs, and other tissues throughout the body. Page thinks these genes could be contributing to the ways in which disease affects men and women differently.
“This paper tells us not only that the Y chromosome is here to stay, but that we need to take it seriously—and not just in the reproductive tract,” says Page.