Y-Autosome Translocation Interferes with Meiotic Sex Inactivation and Expression of Autosomal Genes: A Case Study in the Pig
Laboratoire de Génétique Cellulaire, UMR 444, Institut National de la Recherche Agronomique, Université de Toulouse, Toulouse, France. Sexual Development
(Impact Factor: 2.29).
09/2011; 6(1-3):143-50. DOI: 10.1159/000331477
Y-autosome translocations are rare in humans and pigs. In both species, these rearrangements can be responsible for meiotic arrest and subsequent infertility. Chromosome pairing abnormalities on the SSCX, SSCY and SSC1 chromatin domains were identified by analyzing pachytene spermatocytes from a boar carrying a (Y;1) translocation by immunolocalization of specific meiotic protein combined with FISH. Disturbance of the meiotic sex chromosome inactivation (MSCI) was observed by Cot-RNA-FISH and analysis of ZFY gene expression by sequential RNA- and DNA-FISH on spermatocytes. We hypothesized that the meiotic arrest observed in this boar might be due to the silencing of critical autosomal genes and/or the reactivation of some sex chromosome genes.
Available from: Katarina Siviková
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ABSTRACT: A 9-month-old Yorkshire terrier was admitted to the clinic because of abnormal sexual behaviour and clitoral hypertrophy. External examination confirmed standard development of caudal genital organs: vagina, vulva and cervix uteri. Serum profile of gonadotropin hormones 17 β-estradiol (<10.0 pg.ml(-1)) and testosterone (9.1 ng.ml(-1)) revealed the presence of testicular tissue. A midline laparotomy was performed to detect the cranial parts of the genital system. Gonads resembling testicles, structures indicating epididymis and rudimentary deferent ducts were resected, along with adherent part of the uterus. Cytogenetic analysis showed a male chromosomal complement 78, XY in all metaphases of the studied Yorkshire terrier dog. The chromosomal constitution was confirmed by fluorescence in situ hybridisation (FISH) with whole-chromosome painting probes specific for chromosomes X and Y, as well as by polymerase chain reaction (PCR) amplification of the 271-bp Y-linked fragment of SRY (the sex-determining region on the Y chromosome) gene. Sequencing of the dog's SRY gene coding region did not reveal any mutation. To search for potential mutation in the SOX9 gene (Sry-box containing gene 9), which is considered to be one of the key genes involved in the sex determination process, the PCR fragments of exons 1, 2 and 3 originating from the canine patient were sequenced in order to compare with both male and female healthy control dogs. In the analysed regions of the SOX9 gene, no mutation was found.
Available from: Benny Borremans
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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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