Molecular mechanism of meiotic control : Studies byusing hybrid-sterile organisms.

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Most of hybrid animals are sterile in both male and female due to the meiotic failure in pairing of homologous chromosomes and the recombination. However, the hyburid between yak and cattle shows only male-sterile. The chromosomes, probably the genes also, in both male and female are apparently identical except the sex chromosomes. Thus, we have speculated that the difference in fertility in sex will come from the process for germ cells. Our study indicated (1) in sterile testes, meiotic degradation at pachytene was evident. (2) expression of meiosis specific genes, LIM 9,10,13,15,18, occured even in these degrading meiotic cells, studied by both westem method and in situ FISH method using the antibodies raised against the proteins prepared in E.coli. (3) Optical and electron microscopic studies indicated the presence of normal synaptonema complex except a few segmentations. These results indicate that meiosis proceeds until later half of pachytene normally but then fragmentation of chromosomal DNA,like ones observed in X-autosomal translocation male mice, may be induced. It is interesting to find that as male-sterility recovered by generations, F1, F2, F3 and F4 (noraml fertility) through females, parallels with the percent of normal meiotic cells present in testes and the size of the testes. The molecular mechanisms for male specific failure of meiosis remains to be studied. Nevertheles, this study made a contribution to mongolian breeding research and the basic research for meiosis.