Cytomolecular analysis of chromosome X fragility in subfertile sheep

B. Danielak-Czech, U. Kaczor M. Sharan

Chromosomal fragility is thought to be involved in etiology chromosome aberrations and karyotype evolution and fragile X underlay severe clinical pathology in mammals. The most studied fragile site, observed in cells exposed to mutagens/clastogens such as aphidicolin or folate-deficient conditions, is human FRAXA (co-expressed in Xq27.3 locus with trinicleotide CGG repeat expansion of FRM1 gene) associated with hereditary defects and reproductive dysfunction. In view of that clinical effects of such phenomenon in farm animals are not enough explained we performed cytomolecular analysis of spontaneous and in vitro induced chromosome X instability in sheep with reproductive problems. The studies in subfertile ewes resulted in pointing out chromosome Xq31, Xq33 and Xq22 regions as especially predisposed to structural defects. The latter, OAR Xq22 region comprising fragment of FRM1 gene, with fluorescence in situ labeled, trinucleotide CGG repeats was revealed to be the most unstable in infertile ewes. The results obtained suggest that fertility impairment in sheep may be a consequence of chromosome X fragility in regions comprising loci determining reproductive traits.

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