|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1994 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1993 : ¥1,200,000 (Direct Cost : ¥1,200,000)
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
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