McKearin D, Christerson L
Department of Biochemistry, University of Texas-Southwestern Medical Center, Dallas 75235-9038.
Ciba Found Symp. 1994;182:210-9; discussion 219-22. doi: 10.1002/9780470514573.ch12.
Germ cells frequently develop in syncytial clusters. We are using molecular genetic approaches to the formation of these clusters in Drosophila as a paradigm for cellular differentiation. The genes described in this paper act during an initial step of cluster formation (bag-of-marbles gene [bam]) and near the end of syncytial divisions (orb gene). The results presented suggest that the bam gene product is required for the four incomplete cytokineses that characterize the initial stages of cluster formation. The orb gene, previously identified as an ovarian-specific cDNA which predicts a new member of the RNA-recognition motif family of RNA-binding proteins, is required for both early and late stages of oogenesis. Strong orb alleles arrest egg development at the time of nurse cell-oocyte cyst formation; weak alleles disrupt formation of the anteroposterior and dorsoventral axes within the oocyte during late oogenesis. We postulate that Orb is a constituent of cytoplasmic multiprotein complexes which deliver RNA molecules to specific addresses within the oocyte.
生殖细胞常常在合胞体簇中发育。我们正在利用分子遗传学方法研究果蝇中这些簇的形成，以此作为细胞分化的范例。本文中描述的基因在簇形成的初始步骤（大理石袋基因[bam]）以及合胞体分裂接近尾声时（orb基因）发挥作用。所呈现的结果表明，bam基因产物是簇形成初始阶段所特有的四次不完全胞质分裂所必需的。orb基因先前被鉴定为一种卵巢特异性cDNA，它预测了RNA结合蛋白的RNA识别基序家族的一个新成员，在卵子发生的早期和晚期阶段均是必需的。强orb等位基因在滋养细胞 - 卵母细胞囊肿形成时阻止卵子发育；弱等位基因在卵子发生后期破坏卵母细胞内前后轴和背腹轴的形成。我们推测Orb是细胞质多蛋白复合物的一个组成部分，该复合物将RNA分子递送到卵母细胞内的特定位置。
