Origins and functional evolution of Y chromosomes across mammals

Nature. 2014 Apr 24;508(7497):488-93. doi: 10.1038/nature13151.


Y chromosomes underlie sex determination in mammals, but their repeat-rich nature has hampered sequencing and associated evolutionary studies. Here we trace Y evolution across 15 representative mammals on the basis of high-throughput genome and transcriptome sequencing. We uncover three independent sex chromosome originations in mammals and birds (the outgroup). The original placental and marsupial (therian) Y, containing the sex-determining gene SRY, emerged in the therian ancestor approximately 180 million years ago, in parallel with the first of five monotreme Y chromosomes, carrying the probable sex-determining gene AMH. The avian W chromosome arose approximately 140 million years ago in the bird ancestor. The small Y/W gene repertoires, enriched in regulatory functions, were rapidly defined following stratification (recombination arrest) and erosion events and have remained considerably stable. Despite expression decreases in therians, Y/W genes show notable conservation of proto-sex chromosome expression patterns, although various Y genes evolved testis-specificities through differential regulatory decay. Thus, although some genes evolved novel functions through spatial/temporal expression shifts, most Y genes probably endured, at least initially, because of dosage constraints.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Birds / genetics
  • Conserved Sequence / genetics
  • Evolution, Molecular*
  • Female
  • Gene Dosage / genetics
  • Genes, sry / genetics
  • Genomics
  • High-Throughput Nucleotide Sequencing
  • Male
  • Mammals / genetics*
  • Marsupialia / genetics
  • Receptors, Peptide / genetics
  • Receptors, Transforming Growth Factor beta / genetics
  • Selection, Genetic / genetics
  • Sex Chromosomes / genetics
  • Spatio-Temporal Analysis
  • Spermatogenesis / genetics
  • Testis / metabolism
  • Transcriptome / genetics
  • Y Chromosome / genetics*


  • Receptors, Peptide
  • Receptors, Transforming Growth Factor beta
  • anti-Mullerian hormone receptor

Associated data

  • GEO/GSE50747
  • SRA/SRP026469
  • SRA/SRP029216