Genetic mechanism in hybrid sterility of the mouse

在我们1992年的初步研究中，我们观察到不育（C57BL/6 X m.s prretus） F_1雄性在减数分裂初期（MI）出现了高频率的X/ Y分离（X//Y），并且在回交后代中，X//Y性状作为单个基因分离，该基因与X染色体远端位点Amg相连。为了研究假常染色体区（PAR）在X-Y配对和雄性不育中的作用，我们将携带C57BL/6 （B6）或B6 PAR相反背景的spreus PAR的同源系转移到spreus宿主上。X//Y高、睾丸小或X//Y低、睾丸大的后代在各回交代中分离率几乎为1∶1，其双峰分布与远端X染色体基因标记TeloXY的分离完全相关。此外，在种间杂交雄性中发现了低X/ Y和PAR型纯合子的可育后代，这表明PAR的遗传分化是造成雄性不育的主要原因。在（B6 X m.m ichonicus） F_1雄性中，精子发生在初级精子细胞的早期阶段被阻止，没有观察到任何第一次减数分裂中期。为了探讨C57BL/10杂种雄性不育的遗传机制，我们研究了可育F1雌性与C57BL/10杂交的X-Y解离和回交雄性的不育性。无心肌梗死且睾丸尺寸小、X-Y分离度高且睾丸尺寸小、X-Y分离度低且睾丸尺寸大的三种子代。这一结果表明，除了假常染色体区域外，还有一个或两个常染色体因素控制杂交不育。采用主卫星DNA探针（pMR196）对80例（B6 X M.spretus） F_1 X M.spretus后代和70例（B6 X M.spretus） F_1 X B6后代进行染色体分离分析。结果表明，种间杂交雌性减数分裂过程中不存在随机组合的初始偏差，因为几乎所有的190对配对比较都没有偏离预期，并且在相同（C57BL/6 X M.spretus） F_1杂交雌性的反向回交后代中，相同染色体的偏差没有一致的模式。少

In our initial sutdies (1992) we observed high frequency of X-Y dissociation (X//Y) at first meiotic metaphase (MI) in sterile (C57BL/6 X M.spretus) F_1 males, and that in the backcross progeny the X//Y trait segregated as a single gene which was linked to a distal locus on the X chromosome, Amg. To examine the role of pseudoautosomal region (PAR) in X-Y pairing and male feritility we produced congenic lines that carried the spretus PAR on the C57BL/6 (B6) background or the converse of B6 PAR onto the spretus host. The progeny with either high X//Y and small testis size or low X//Y and large testis size segregated almost 1 : 1 in each succeeding backcross generation, and the bimodal distribution was completely correlated with the segregation of the distal X chromosome gene marker, TeloXY.Furthermore, fertile progeny with low X//Y and homozygous PAR-type were found in mating M.spretus males with female miece of the congenic line, this result showing that the genetic divergence of PAR is … More a major contribution to the male sterility observed in interspecific hybrid males.Spermatogenesis is arrested in earlier stage of primary spermatocytes and any first meiotic metaphase are not observed in (B6 X M.macedonicus) F_1 males. To examine genetic mechanism of male sterility in the hybrid, we examined X-Y dissociation and sterility in backcross males from fertile F1 females crossed with C57BL/10. Three types of progeny were found as follows : progeny with no MI and small testis size, high X-Y dissociation and small testis size, and low X-Y dissociation and large testis size. This result indicates that there are one or two autosomal factors, which controls hybrid sterility, in addition to the pseudoautosomal region.Chromosomal segregation was analyzed in 80 (B6 X M.spretus) F_1 X M.spretus progeny and 70 (B6 X M.spretus) F_1 X B6 progeny using FISH analysis with a major satellite DNA probe (pMR196). The results suggested that there was not primary deviation from random assortment during meiosis in the interspecific hybrid female, because nearly all of the 190 pair-wise comparisons did not deviate from expected and because there was no consistent pattern of deviation of the same chromosomes in the reciprocal backcross progeny from similar (C57BL/6 X M.spretus) F_1 hybrid females. Less