Dosage compensation of the active X chromosome in mammals

Nat Genet. 2006 Jan;38(1):47-53. doi: 10.1038/ng1705. Epub 2005 Dec 11.

Abstract

Monosomy of the X chromosome owing to divergence between the sex chromosomes leads to dosage compensation mechanisms to restore balanced expression between the X and the autosomes. In Drosophila melanogaster, upregulation of the male X leads to dosage compensation. It has been hypothesized that mammals likewise upregulate their active X chromosome. Together with X inactivation, this mechanism would maintain balanced expression between the X chromosome and autosomes and between the sexes. Here, we show that doubling of the global expression level of the X chromosome leads to dosage compensation in somatic tissues from several mammalian species. X-linked genes are highly expressed in brain tissues, consistent with a role in cognitive functions. Furthermore, the X chromosome is expressed but not upregulated in spermatids and secondary oocytes, preserving balanced expression of the genome in these haploid cells. Upon fertilization, upregulation of the active X must occur to achieve the observed dosage compensation in early embryos.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Brain / physiology
  • Dosage Compensation, Genetic*
  • Drosophila / genetics
  • Embryonic Development / genetics
  • Female
  • Gene Expression Regulation, Developmental
  • Humans
  • Male
  • Mammals / genetics*
  • Mice
  • Oocytes / physiology
  • Spermatids / physiology
  • Up-Regulation
  • X Chromosome / genetics*
  • X Chromosome Inactivation