Larkin M K, Holder K, Yost C, Giniger E, Ruohola-Baker H
Department of Biochemistry, University of Washington, Seattle 98195-7350, USA.
Development. 1996 Nov;122(11):3639-50. doi: 10.1242/dev.122.11.3639.
During early development, there are numerous instances where a bipotent progenitor divides to give rise to two progeny cells with different fates. The Notch gene of Drosophila and its homologues in other metazoans have been implicated in many of these cell fate decisions. It has been argued that the role of Notch in such instances may be to maintain cells in a precursor state susceptible to specific differentiating signals. This has been difficult to prove, however, due to a lack of definitive markers for precursor identity. We here perform molecular and morphological analyses of the roles of Notch in ovarian follicle cells during Drosophila oogenesis. These studies show directly that constitutively active Notch arrests cells at a precursor stage, while the loss of Notch function eliminates this stage. Expression of moderate levels of activated Notch leads to partial transformation of cell fates, as found in other systems, and we show that this milder phenotype correlates with a prolonged, but still transient, precursor stage. We also find that expression of constitutively active Notch in follicle cells at later stages leads to a defect in the anterior-posterior axis of the oocyte.
在早期发育过程中，有许多双能祖细胞分裂产生两个命运不同的子代细胞的例子。果蝇的Notch基因及其在其他后生动物中的同源物与许多此类细胞命运决定有关。有人认为，Notch在这些情况下的作用可能是使细胞维持在前体状态，易于接受特定的分化信号。然而，由于缺乏前体身份的确切标记，这一点很难得到证实。我们在此对果蝇卵子发生过程中Notch在卵巢滤泡细胞中的作用进行了分子和形态学分析。这些研究直接表明，组成型激活的Notch使细胞停滞在前体阶段，而Notch功能的丧失则消除了这个阶段。适度水平的激活Notch的表达会导致细胞命运的部分转变，正如在其他系统中所发现的那样，并且我们表明这种较温和的表型与延长但仍然短暂的前体阶段相关。我们还发现，在后期滤泡细胞中组成型激活的Notch的表达会导致卵母细胞前后轴出现缺陷。
