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.spretus)F_1在减数分裂中期(MI)的X-Y解离(X//Y)频率很高，而在回交后代中，X//Y性状分离为单基因，该基因与X染色体上的一个远端基因AMG连锁。为了研究伪常染色体区域(PAR)在X-Y配对和雄性育性中的作用，我们建立了在C57BL/6(B6)背景上携带Spretus PAR的同源系，或在Spretus宿主上携带B6 PAR的同源系。高X//Y和小精巢或低X//Y和大X/Y的后代在每个回交世代中的分离比例几乎为1：1，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，在与同源系雌性后代交配的Spretus中发现了可育的低X//Y和纯合子Par类型的后代，这表明PAR的遗传分化是…在(B6×M.macedonicus)F_1雄性中，精子发生受阻于初级精母细胞的早期，没有观察到第一次减数分裂中期。为了探讨杂交种雄性不育的遗传机制，我们对C57BL/10与可育F_1代杂交后代的X-Y分离和不育进行了检测。结果表明，有三种类型的后代：无MI且睾丸较小的后代，X-Y分离较高且睾丸较小的后代，以及X-Y分离较低且睾丸较大的后代。对80个(B6×M.spretus)F1×M.spretus子代和70个(B6×M.spretus)F1×B6子代的染色体分离进行了FISH分析。结果表明，在种间杂种雌体减数分裂过程中，几乎所有的190对配对比较都没有偏离预期，并且与相似的(C57BL/6×M.spretus)F_1代的正反交后代没有一致的染色体偏离模式，因此在减数分裂过程中没有初步偏离随机分类。较少

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