Chromosomal aspects and inheritance of the XY female condition in Akodon azarae (Rodentia, Sigmodontinae)

Abstract

The populations of several species of Akodon present, besides XX females, a variable proportion of fertile XY females. In Akodon azarae, a correspondence exists between the X-chromosome C-banding pattern and the sexual phenotype of XY individuals: males carry a determinate X-chromosome type, defined by its C-banding pattern, and XY females, any of two others. To confirm the relation between X-chromosome type and the XY female condition and to investigate the hereditary transmission of these different X-chromosomes, we analyzed 50 animals captured in the field and 95 individuals corresponding to the F 1 and F 2 offspring of 16 crosses.It was seen that the correlation between X type and the sexual phenotype of XY animals is retained, and that the three X types are transmitted to the progeny. It was also observed that the male offspring of XY females receive the X-chromosome from their male parents and the Y from their mothers. These results strongly support the causal role of an X-borne mutation in A. azarae XY sex reversal, and discard a mutation of the Y-chromosome as the sole basis of this phenomenon.

A novel sex determination system in a close relative of the house mouse

“…It is noteworthy that similar, atypical sex determination systems have been described in three other rodent genera (see §1). The genetic bases of these modifications are all unknown, but are associated with an X-linked mutation in Myopus (deletion of Xp 21 -23 ; Liu et al 1998), and possibly so too in Dicrostonyx and Akodon (Fredga 1988;Ortiz et al 2009). Although these mutations have appeared independently in the four different lineages (even the two lemmings are not closely related; Buzan et al 2008), they are all X-linked, and may therefore involve the same gene(s).…”

“…So far, these unusual sex-determining systems have been unambiguously identified by molecular or cytogenomic methods in seven genera, all rodents, which group in four categories: (i) XX or XY females and XY males in the lemmings Myopus schisticolor and Dicrostonyx torquatus (Fredga et al 1976;Fredga 1983Fredga , 1988Fredga , 1994, as well as several species of the South-American field mouse Akodon sp. (Hoekstra & Edwards 2000;Bianchi 2002;Ortiz et al 2009); (ii) XO females (only one X) and XY males in the vole Microtus oregoni (Ohno et al 1963(Ohno et al , 1966Fredga 1983); (iii) females and males with an identical XO karyotype (loss of the second X chromosome in females and of the Y in males) in the Japanese spiny rats Tokudaia osimensis and Tokudaia tokunoshimensis (Soullier et al 1998;Sutou et al 2001;Arakawa et al 2002), and the mole vole Ellobius lutescens (Matthey 1953;Just et al 1995Just et al , 2007, and finally; (iv) XX males and females in two other species of Ellobius, E. tancrei and E. talpinus (Just et al 1995(Just et al , 2007. Categories (iii) and (iv) are remarkable since sex determination occurs in the absence of a Y chromosome, and even without the Sry gene.…”

Sexual dimorphism in prophase I of meiosis in the Northern mole vole (Ellobius talpinus Pallas, 1770) with isomorphic (XX) chromosomes in males and females

“…There are at least four types of deviations (Veyrunes et al, 2010): (1) typical XY males and different females with XX and XY in Myopus schisticolor Lilljeborg, 1844, Dicrostonyx torquatus Pallas, 1778, Akodon sp. (Fredga, 1983(Fredga, , 1994Hoekstra, Edwards 2000;Ortiz et al, 2009); (2) typical XY males and deviant XO females (single X) in Microtus oregoni Bachman, 1839 (Ohno et al, 1966;Fredga, 1983); (3) females and males with XO karyotypes in Tokudaia osimensis Abe, 1933, T. tokunoshimensis Endo et Tsuchiya, 2006(Arakawa et al, 2002 and Ellobius lutescens Thomas, 1897 (Matthey 1953;Just et al, 1995); (4) males and females with identical isomorphic XX in three sibling species of Ellobius, E. tancrei Blasius, 1884, E. talpinus Pallas, 1770 and E. alaicus Vorontsov et al, 1969(Vorontsov et al, 1980Bakloushinskaya, Lyapunova, 1990;Just et al, 2007;Romanenko et al, 2007).…”

No Differences in the Sry Gene between Males and XY Females in Akodon (Rodentia, Cricetidae)

“…Three C-banding patterns of the X chromosome can be seen in this species [Ortiz et al, 1998]: Males always have an X 1 type, whereas XY females have any of the other two (X 2 or X 3 ); XX females present an X 1 gonosome, the other being of any of the types. On this basis, recent evidence about the hereditary transmission of the various X types points to an X chromosome mutation as being the origin of this condition [Ortiz et al, 2009]. In the current study, we have sequenced the Sry gene of A. azarae and A. boliviensis , including the complete ORF, and found no significant differences between males and XY females, which rules out the possibility of a Sry mutation being the sole cause of the XY female phenotype.…”