Mammalian Y chromosomes retain widely expressed dosage-sensitive regulators
Abstract
The human X and Y chromosomes evolved from an ordinary pair
of autosomes, but millions of years ago genetic decay ravaged the Y
chromosome, and only three per cent of its ancestral genes survived. We
reconstructed the evolution of the Y chromosome across eight mammals to
identify biases in gene content and the selective pressures that
preserved the surviving ancestral genes. Our findings indicate that
survival was nonrandom, and in two cases, convergent across placental
and marsupial mammals. We conclude that the gene content of the Y
chromosome became specialized through selection to maintain the
ancestral dosage of homologous X–Y gene pairs that function as broadly
expressed regulators of transcription, translation and protein
stability. We propose that beyond its roles in testis determination and
spermatogenesis, the Y chromosome is essential for male viability, and
has unappreciated roles in Turner’s syndrome and in phenotypic
differences between the sexes in health and disease.
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