Specific patterns of histone marks accompany X chromosome inactivation in a marsupial |
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Authors: | Edda Koina Julie Chaumeil Ian K. Greaves David J. Tremethick Jennifer A. Marshall Graves |
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Affiliation: | (1) Research School of Biological Sciences, The Australian National University, Canberra, ACT, 0200, Australia;(2) The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, 0200, Australia |
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Abstract: | The inactivation of one of the two X chromosomes in female placental mammals represents a remarkable example of epigenetic silencing. X inactivation occurs also in marsupial mammals, but is phenotypically different, being incomplete, tissue-specific and paternal. Paternal X inactivation occurs also in the extraembryonic cells of rodents, suggesting that imprinted X inactivation represents a simpler ancestral mechanism. This evolved into a complex and random process in placental mammals under the control of the XIST gene, involving notably variant and modified histones. Molecular mechanisms of X inactivation in marsupials are poorly known, but occur in the absence of an XIST homologue. We analysed the specific pattern of histone modifications using immunofluorescence on metaphasic chromosomes of a model kangaroo, the tammar wallaby. We found that all active marks are excluded from the inactive X in marsupials, as in placental mammals, so this represents a common feature of X inactivation throughout mammals. However, we were unable to demonstrate the accumulation of inactive histone marks, suggesting some fundamental differences in the molecular mechanism of X inactivation between marsupial and placental mammals. A better understanding of the epigenetic mechanisms underlying X inactivation in marsupials will provide important insights into the evolution of this complex process. Edda Koina and Julie Chaumeil contributed equally to this work. |
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Keywords: | dosage compensation epigenetic silencing tammar wallaby Macropus eugenii X inactivation |
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