Ohsako Takashi, Hirai Kazuyuki, Yamamoto Masa-Toshi
Drosophila Genetic Resource Center, Kyoto Institute of Technology, Saga Ippongi-cho, Ukyo-ku, Kyoto 816-8354, Japan.
Genes Genet Syst. 2003 Jun;78(3):253-66. doi: 10.1266/ggs.78.253.
The male sterile mutation, misfire (mfr), of Drosophila melanogaster is a novel paternal effect, fertilization defective mutant that effects sperm head decondensation. mfr sperm were motile, appeared normal morphologically and were transferred to the female during copulation. However, less than 0.1% of eggs laid by females mated to mfr males hatched. Although mfr sperm entered eggs at a high frequency (93%), 99% of the inseminated eggs did not initiate the first nuclear division. Unlike wild type fertilizing sperm, the position and shape of mfr sperm tails within the egg were not constant, but varied in a seemingly random manner. The heads of inseminating mutant sperm were always located near the surface of eggs just underlying the egg plasma membrane, and maintained their needle-like shape indicating the failure of nuclear decondensation. Further observations revealed that plasma membrane of inseminating sperm appeared intact, including the head region. These phenotypes were equivalent to those of sneaky (snky), another fertilization defective male sterile mutation. Our observations strongly suggest that mfr mutant males are sterile because their inseminating sperm fail to form a male pronucleus due to the inability of the sperm to properly respond to egg factors responsible for the breakdown of the plasma membrane. Although mfr and snky mutations were phenotypically identical, they mapped to cytologically distinct genetic loci and no genetic interactions were observed, suggesting that at least two distinct paternal gene products are involved in the early stages of pronuclear formation.
黑腹果蝇的雄性不育突变体“misfire”（mfr）是一种新型的父本效应、受精缺陷型突变体，它会影响精子头部去浓缩。mfr精子具有运动能力，形态上看似正常，并且在交配时会转移到雌蝇体内。然而，与mfr雄蝇交配的雌蝇所产的卵中，孵化出的不到0.1%。尽管mfr精子以较高频率（93%）进入卵子，但99%的受精卵子并未启动第一次核分裂。与野生型受精精子不同，mfr精子尾部在卵子内的位置和形状并不恒定，而是以一种看似随机的方式变化。授精突变精子的头部总是位于卵子质膜下方的卵表面附近，并保持其针状形态，这表明核去浓缩失败。进一步观察发现，授精精子的质膜，包括头部区域，看起来是完整的。这些表型与另一种受精缺陷型雄性不育突变体“sneaky”（snky）的表型相同。我们的观察结果强烈表明，mfr突变雄蝇不育是因为它们的授精精子由于无法对负责质膜破裂的卵子因子做出适当反应而未能形成雄原核。尽管mfr和snky突变在表型上相同，但它们定位于细胞学上不同的基因座，并且未观察到遗传相互作用，这表明至少有两种不同的父本基因产物参与原核形成的早期阶段。
