Comparative FISH mapping of bovid X chromosomes reveals homologies and divergences between the subfamilies Bovinae and Caprinae

Comparative FISH mapping of river buffalo (Bubalus bubalis, BBU), sheep (Ov is aries, OAR), and cattle (Bos taurus, BTA) X chromosomes revealed homolog ies and divergences between the X chromosomes in the subfamilies Bovinae an d Caprinae, Twenty-four and 17 loci were assigned for the first time to BBU X and OAR X, respectively, noticeably extending the physical map in these two species. Seventeen loci (four of which for the first time) were also FI SH mapped to BTA X and used for comparative mapping studies on the three sp ecies, which show three morphologically different X chromosomes: an acrocen tric (BBU X), an acrocentric with distinct short arms (OAR X), and a submet acentric (BTA X). The same order of loci were found on BTA X and BBU X, sug gesting that a centromere transposition, with loss (cattle) or acquisition (river buffalo) of constitutive heterochromatin, differentiated the X chrom osomes of these two bovids. Comparison of bovine (cattle and river buffalo) and caprine (sheep)X chromosomes revealed at least five common chromosome segments, suggesting that multiple transpositions, with retention or loss o f constitutive heterochromatin, had occurred during their karyotypic evolut ion. Copyright (C) 2000 S. Karger AG, Basel.