Veyrunes F, Perez J, Borremans B, Gryseels S, Richards LR, Duran A, Chevret P, Robinson TJ, Britton-Davidian J. A new cytotype of the African pygmy mouse Mus minutoides in Eastern Africa. Implications for the evolution of sex-autosome translocations.
Chromosome Res 2014;
22:533-43. [PMID:
25159220 DOI:
10.1007/s10577-014-9440-x]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 07/31/2014] [Accepted: 08/17/2014] [Indexed: 11/27/2022]
Abstract
The African pygmy mice (genus Mus, subgenus Nannomys) are recognized for their highly conserved morphology but extensive chromosomal diversity, particularly involving sex-autosome translocations, one of the rarest chromosomal rearrangements among mammals. It has been shown that in the absence of unambiguous diagnostic morphological traits, sex-autosome translocations offer accurate taxonomic markers. For example, in Mus minutoides, irrespective of the diploid number (which ranges from 2n = 18 to 34), all specimens possess the sex-autosome translocations (X.1) and (Y.1) that are unique to this species. In this study, we describe a new cytotype that challenges this view. Males are characterized by the translocation (Y.1) only, while females carry no sex-autosome translocation, the X chromosome being acrocentric. Hence, although sex-autosome translocations (X.1) and (Y.1) are still diagnostic when one or both are present, their absence does not rule out M. minutoides. This cytotype has a large distribution, with specimens found in Tanzania and in the eastern part of South Africa. The nonpervasive distribution of Rb(X.1) provides an opportunity to investigate different evolutionary scenarios of sex-autosome translocations using a phylogenetic framework and the distribution of telomeric repeats. The results tend to support a scenario involving a reversal event, i.e., fusion then fission of Rb(X.1), and highlighted the existence of a new X1X1X2X2/X1X2Y sex chromosome system, confirming the remarkable diversity of neo-sex chromosomes and sex determination systems in the African pygmy mice.
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