title: A new cytotype of the African pygmy mouse Mus minutoides in Eastern Africa. Implications for the evolution of sex-autosome translocations.
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.
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2, UMR CNRS 5554, Montpellier, France, frederic.veyrunes@univ-montp2.fr.
authors.forename: F
authors.initials: F
authors.lastname: Veyrunes
authors.forename: J
authors.initials: J
authors.lastname: Perez
authors.forename: B
authors.initials: B
authors.lastname: Borremans
authors.forename: S
authors.initials: S
authors.lastname: Gryseels
authors.forename: L R
authors.initials: LR
authors.lastname: Richards
authors.forename: A
authors.initials: A
authors.lastname: Duran
authors.forename: P
authors.initials: P
authors.lastname: Chevret
authors.forename: T J
authors.initials: TJ
authors.lastname: Robinson
authors.forename: J
authors.initials: J
authors.lastname: Britton-Davidian
mesh_terms: D000351:Africa, Eastern; D000818:Animals; D005075:Biological Evolution; D002869:Chromosome Aberrations; D033481:Chromosomes, Mammalian; D005260:Female; D007621:Karyotyping; D008297:Male; D051379:Mice; D010802:Phylogeny; D014178:Translocation, Genetic / Q000235:genetics*; D014960:X Chromosome / Q000235:genetics*