Meiotic inactivation of chromatin in spermatocytes of interspecific hybrids of mole-voles Ellobius

Abstract

Aims: Аnalysis of synapsis and meiotic inactivation of chromosomes in the prophase I nuclei of spermatocytes of sterile interspecific hybrids of mole-voles. Methods. We used a surface-spreading and immunocytochemical techniques to visualize the process of chromosome synapsis with antibodies to protein SCP3 and for analysis of MSUC (meiotic silencing of unsynapsed chromatin) with antibodies to γH2AX. Results. The meiotic chromosome synapsis and silencing of unsynapsed chromatin of autosomes and sex chromosomes have been examined in spermatocytes of interspecific hybrid E. talpinus (2n=NF=54) and E. tancrei (2n=32; NF=56), heterozygous for eleven Robertsonian (Rb) translocations. The pachytene spermatocytes had normal bivalents; open and close SC trivalents, chains of chromosomes with lengthy unsynapsed regions. Chromatin of unsynapsed regions associated with extensive clouds of γH2AX. However, they are not eliminated during pachytene and most of them proceed into diplotene. The sex bivalent formed sex body in many nucleus and associated with γH2AX. So, synapsis defects in most pachytene cells did not trigger a pachytene arrest. Analysis of suspension of testicular cell and histological study of testicular tissue hasn't revealed any spermatids or spermatozoids. Conclusions. The spermatocytes heterozygous for eleven Robertsonian translocations overcame pachytene and were exposed to arrest at later stages of spermatogenesis. These results serve as one more explanation of a wide circulation of Rb-translocations in populations of many animal species.

Key words: Rb translocation, Ellobius, synaptonemal complex, γH2AX, interspecific hybrids, sterility.