Strict evolutionary conservation followed rapid gene loss on human and rhesus Y chromosomes
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Author(s)
Hughes, Jennifer F.
Skaletsky, Helen
Brown, Laura G.
Pyntikova, Tatyana
Graves, Tina
Fulton, Robert S.
Dugan, Shannon
Ding, Yan
Buhay, Christian J.
Kremitzki, Colin
Date Issued
February 2012
Journal
Nature
Publisher
Nature Publishing Group
Citation
Hughes, Jennifer F. et al. “Strict Evolutionary Conservation Followed Rapid Gene Loss on Human and Rhesus Y Chromosomes.” Nature 483.7387 (2012): 82–86.
Version
Author's final manuscript
Abstract
The human X and Y chromosomes evolved from an ordinary pair of autosomes during the past 200–300 million years[superscript 1, 2, 3]. The human MSY (male-specific region of Y chromosome) retains only three percent of the ancestral autosomes’ genes owing to genetic decay[superscript 4, 5]. This evolutionary decay was driven by a series of five ‘stratification’ events. Each event suppressed X–Y crossing over within a chromosome segment or ‘stratum’, incorporated that segment into the MSY and subjected its genes to the erosive forces that attend the absence of crossing over[superscript 2, 6]. The last of these events occurred 30 million years ago, 5 million years before the human and Old World monkey lineages diverged. Although speculation abounds regarding ongoing decay and looming extinction of the human Y chromosome[superscript 7, 8, 9, 10], remarkably little is known about how many MSY genes were lost in the human lineage in the 25 million years that have followed its separation from the Old World monkey lineage. To investigate this question, we sequenced the MSY of the rhesus macaque, an Old World monkey, and compared it to the human MSY. We discovered that during the last 25 million years MSY gene loss in the human lineage was limited to the youngest stratum (stratum 5), which comprises three percent of the human MSY. In the older strata, which collectively comprise the bulk of the human MSY, gene loss evidently ceased more than 25 million years ago. Likewise, the rhesus MSY has not lost any older genes (from strata 1–4) during the past 25 million years, despite its major structural differences to the human MSY. The rhesus MSY is simpler, with few amplified gene families or palindromes that might enable intrachromosomal recombination and repair. We present an empirical reconstruction of human MSY evolution in which each stratum transitioned from rapid, exponential loss of ancestral genes to strict conservation through purifying selection.
MIT Department
Massachusetts Institute of Technology. Department of Biology
Whitehead Institute for Biomedical Research
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DOI of Published Version
https://doi.org/10.1038/nature10843
