Rübsam R, Hollmann M, Simmerl E, Lammermann U, Schäfer M A, Büning J, Schäfer U
Zoologisches Institut I, Universität Erlangen, Staudtstr. 5, D-91058, Erlangen, Germany.
Mech Dev. 1998 Mar;72(1-2):131-40. doi: 10.1016/s0925-4773(98)00023-9.
Oogenesis in Drosophila is a useful model for studying cell differentiation. We have analyzed the role of the egh gene in these processes with the aid of a newly isolated viable but female sterile allele. This mutation results in diverse variable defects in oogenesis. The most frequent defect being follicles that have either more or less than the normal number of 16 germ cells. This is caused by erroneous splitting and/or fusion of correct clusters of 16 cystocytes. The entire follicle has a rather flexible structure in this allele, most obvious by a highly variable position of the oocyte within the follicle. Moreover, a second oocyte can also develop in egh clusters. This is exclusively observed in aberrant follicles that are generated by the aforementioned splitting/fusion process. Surprisingly, even a germ cell which is distinct from the two pro-oocytes can differentiate into an oocyte under these circumstances. Hence, determination of the oocyte is definitely not fixed when germ cell clusters are enveloped by prefollicular cells, and interactions between follicle cells and germ cells must play an important role in oocyte specification. Molecular analysis proves that the oocyte-specific transcript of the egh gene is drastically reduced in this viable allele.
果蝇的卵子发生是研究细胞分化的一个有用模型。我们借助新分离出的一个可存活但雌性不育的等位基因，分析了egh基因在这些过程中的作用。这种突变在卵子发生过程中导致了多种不同的缺陷。最常见的缺陷是卵泡中生殖细胞的数量多于或少于正常的16个。这是由16个囊细胞的正确簇错误分裂和/或融合引起的。在这个等位基因中，整个卵泡结构相当灵活，最明显的表现是卵泡内卵母细胞的位置高度可变。此外，在egh簇中也会发育出第二个卵母细胞。这仅在由上述分裂/融合过程产生的异常卵泡中观察到。令人惊讶的是，在这种情况下，即使是与两个前卵母细胞不同的生殖细胞也能分化为卵母细胞。因此，当生殖细胞簇被卵泡前体细胞包裹时，卵母细胞的决定显然不是固定的，卵泡细胞和生殖细胞之间的相互作用必定在卵母细胞特化中起重要作用。分子分析证明，在这个可存活的等位基因中，egh基因的卵母细胞特异性转录本大幅减少。
