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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
Evolution from XIST-independent to XIST-controlled X-chromosome inactivation: Epigenetic modifications in distantly related mammals
PLoS ONE, Volume 6, No. 4, Article e19040, Year 2011
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Description
X chromosome inactivation (XCI) is the transcriptional silencing of one X in female mammals, balancing expression of X genes between females (XX) and males (XY). In placental mammals non-coding XIST RNA triggers silencing of one X (Xi) and recruits a characteristic suite of epigenetic modifications, including the histone mark H3K27me3. In marsupials, where XIST is missing, H3K27me3 association seems to have different degrees of stability, depending on cell-types and species. However, the complete suite of histone marks associated with the Xi and their stability throughout cell cycle remain a mystery, as does the evolution of an ancient mammal XCI system. Our extensive immunofluorescence analysis (using antibodies against specific histone modifications) in nuclei of mammals distantly related to human and mouse, revealed a general absence from the mammalian Xi territory of transcription machinery and histone modifications associated with active chromatin. Specific repressive modifications associated with XCI in human and mouse were also observed in elephant (a distantly related placental mammal), as was accumulation of XIST RNA. However, in two marsupial species the Xi either lacked these modifications (H4K20me1), or they were restricted to specific windows of the cell cycle (H3K27me3, H3K9me2). Surprisingly, the marsupial Xi was stably enriched for modifications associated with constitutive heterochromatin in all eukaryotes (H4K20me3, H3K9me3). We propose that marsupial XCI is comparable to a system that evolved in the common therian (marsupial and placental) ancestor. Silent chromatin of the early inactive X was exapted from neighbouring constitutive heterochromatin and, in early placental evolution, was augmented by the rise of XIST and the stable recruitment of specific histone modifications now classically associated with XCI. © 2011 Chaumeil et al.
Authors & Co-Authors
Chaumeil, Julie
Australia, Canberra
Anu Research School of Biology
United States, New York
Nyu Grossman School of Medicine
Waters, Paul D.
Australia, Canberra
Anu Research School of Biology
Koina, Edda
Australia, Canberra
Anu Research School of Biology
Gilbert, Clément
South Africa, Stellenbosch
Stellenbosch University
United States, Arlington
The University of Texas at Arlington
Robinson, Terence J.
South Africa, Stellenbosch
Stellenbosch University
Graves, Jennifer A.Marshall
Australia, Canberra
Anu Research School of Biology
Statistics
Citations: 64
Authors: 6
Affiliations: 4
Identifiers
Doi:
10.1371/journal.pone.0019040
e-ISSN:
19326203
Participants Gender
Female