RESUMO
In a Brazilian population of the neotropical rodent Akodon montensis we found five sex-reversed XY females. These animals were cytogenetically analyzed by chromosome painting using species-specific DNA probes from the Y chromosome, generated by chromosomal microdissection and subsequent use of the degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR). The results showed a chromosome complement with an apparently normal Y chromosome and an X chromosome carrying a translocation that encompasses a large portion of the Y chromosome (seemingly the entire Y). Ovarian histology suggested that these females are fertile. Amplification of the SRY HMG box sequence by PCR shows that at least one copy of the Sry gene is present in the A. montensis XY females. Based on our findings, we suggest that the breakpoint of the X;Y translocation probably altered an X-linked sex-determining locus (or loci), blocking testicular organogenesis in the XY females. Further studies are necessary to determine the precise location and role of this putative sex-determining chromosomal region. Genetic mechanisms of XY sex reversal in A. montensis populations are discussed.
Assuntos
Coloração Cromossômica , Fertilidade/genética , Muridae/genética , Proteínas Nucleares , Fatores de Transcrição , Translocação Genética/genética , Cromossomo X/genética , Cromossomo Y/genética , Motivos de Aminoácidos , Animais , Brasil , Bandeamento Cromossômico , Quebra Cromossômica/genética , Sondas de DNA/genética , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Diploide , Transtornos do Desenvolvimento Sexual , Feminino , Dosagem de Genes , Heterocromatina/genética , Cariotipagem , Masculino , Ovário/patologia , Reação em Cadeia da Polimerase , Processos de Determinação Sexual , Proteína da Região Y Determinante do SexoRESUMO
The neotropical rodents Akodon cursor (2n = 14, 15, and 16) and A. montensis (2n = 24 and 25), two closely related and morphologically indistinguishable species, have been compared by G-banding and chromosome painting. In situ hybridization of a biotinylated DOP-PCR product obtained from a microdissected chromosome of A. cursor onto A. montensis chromosomes was performed in combination with localization of telomeric sequences using a (TTAGGG)n oligomer as a FISH probe. The results provide evidence of the complex chromosomal rearrangements suggested by GTG-banding analysis, indicating the origin of one A. cursor autosome from three different A. montensis autosomes. Furthermore, the complete cytogenetic homeology between the A. cursor and A. montensis karyotypes was determined, along with the occurrence of tandem fusions and pericentric inversions and the loss of telomeres, centromeres, and chromosome arms. Evidence for the ancestral origin of the A. cursor karyotype is also provided.