Genes flanking Xist in mouse and human are separated on the X chromosome in American marsupialsReportar como inadecuado

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Chromosome Research

, 15:127

First Online: 05 March 2007Received: 27 October 2006Revised: 13 December 2006Accepted: 13 December 2006


X inactivation, the transcriptional silencing of one of the two X chromosomes in female mammals, achieves dosage compensation of X-linked genes relative to XY males. In eutherian mammals X inactivation is regulated by the X-inactive specific transcript Xist, a cis-acting non-coding RNA that triggers silencing of the chromosome from which it is transcribed. Marsupial mammals also undergo X inactivation but the mechanism is relatively poorly understood. We set out to analyse the X chromosome in Monodelphis domestica and Didelphis virginiana, focusing on characterizing the interval defined by the Chic1 and Slc16a2 genes that in eutherians flank the Xist locus. The synteny of this region is retained on chicken chromosome 4 where other loci belonging to the evolutionarily ancient stratum of the human X chromosome, the so-called X conserved region XCR, are also located. We show that in both M. domestica and D. virginiana an evolutionary breakpoint has separated the Chic1 and Slc16a2 loci. Detailed analysis of opossum genomic sequences revealed linkage of Chic1 with the Lnx3 gene, recently proposed to be the evolutionary precursor of Xist, and Fip1, the evolutionary precursor of Tsx, a gene located immediately downstream of Xist in eutherians. We discuss these findings in relation to the evolution of Xist and X inactivation in mammals.

Key wordsDidelphis virginiana marsupial Monodelphis domestica opossum X chromosome X inactivation Xist  Download fulltext PDF

Autor: Alexander I. Shevchenko - Irina S. Zakharova - Eugeny A. Elisaphenko - Nicolay N. Kolesnikov - Siobhan Whitehead - Christ


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