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Sex chromosome silencing in the marsupial male germ line

Year: 2007

Type: article

Abstract: In marsupials, dosage compensation involves silencing of the father's X-chromosome. Because no XIST orthologue has been found, how imprinted X-inactivation occurs is unknown. In eutherians, the X is subject to meiotic sex chromosome inactivation (MSCI) in the paternal germ line and persists thereafter as postmeiotic sex chromatin (PMSC). One hypothesis proposes that the paternal X is inherited by the eutherian zygote as a preinactive X and raises the possibility of a similar process in the marsupial germ line. Here we demonstrate that MSCI and PMSC occur in the opossum. Surprisingly, silencing occurs before X-Y association. After MSCI, the X and Y fuse through a dense plate without obvious synapsis. Significantly, sex chromosome silencing continues after meiosis, with the opossum PMSC sharing features of eutherian PMSC. These results reveal a common gametogenic program in two diverse clades of mammals and support the idea that male germ-line silencing may have provided an ancestral form of mammalian dosage compensation.

Source: Proceedings of the National Academy of Sciences

DOI: 10.1073/pnas.0700323104

Authors: Satoshi H. Namekawa, John L. VandeBerg, John R. McCarrey, Jeannie T. Lee

Institutions: Howard Hughes Medical Institute, Harvard University, Massachusetts General Hospital, Texas Biomedical Research Institute, The University of Texas at San Antonio

Language: English

Topic: Genetic and Clinical Aspects of Sex Determination and Chromosomal Abnormalities

Subfield: Genetics

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

Open Access status: green