Dosage compensation of the active X chromosome in mammals.

TLDR: It is shown that doubling of the global expression level of the X chromosome leads to dosage compensation in somatic tissues from several mammalian species.

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