Lessons from comparative analysis of X-chromosome inactivation in mammals.
In most mammals, X-chromosome inactivation is used as the strategy to achieve dosage compensation between XX females and XY males. This process is developmentally regulated, resulting in the differential treatment of the two X chromosomes in the same nucleus and mitotic heritability of the silent state. A lack of dosage compensation in an XX embryo is believed to result in early lethality, at least in eutherians. Given its fundamental importance, X-chromosome inactivation would be predicted to be a highly conserved process in mammals. However, recent studies have revealed major mechanistic differences in X inactivation between eutherians and marsupials, suggesting that the evolution of the X chromosome as well as developmental differences between mammals have led to diverse evolutionary strategies for dosage compensation.
Mammalian Developmental Epigenetics Group, Institut Curie, CNRS UMR3215 INSERM U934, 26 rue d'Ulm, 75248 Paris Cedex 05, France. ikuhiro.Okamoto@curie.fr
Ikuhiro
I
Okamoto
Edith
E
Heard
D000818:Animals; D005075:Biological Evolution; D044127:Epigenesis, Genetic; D005260:Female; D020868:Gene Silencing; D006801:Humans; D008297:Male; D008322:Mammals / Q000235:genetics*; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics; D049951:X Chromosome Inactivation
D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; C077885:XIST non-coding RNA