Hawkins N C, Thorpe J, Schüpbach T
Department of Molecular Biology, Howard Hughes Medical Institute, Princeton University, New Jersey 08544, USA.
Development. 1996 Jan;122(1):281-90. doi: 10.1242/dev.122.1.281.
During Drosophila oogenesis, a stem cell daughter undergoes precisely four rounds of mitosis to generate a cyst of 16 cells interconnected by cytoplasmic bridges. One of the cells becomes the oocyte while the remaining 15 cells differentiate as nurse cells. We hve identified a gene, encore, that is involved both in regulating the number of germline mitoses and in the process of oocyte differentation. Mutations in encore result in exactly one extra round of mitosis in the germline. Genetic and molecular studies indicate that this mitotic defect may be mediated through the gene bag-of-marbles. The isolation and characterization of multiple alleles of encore revealed that they were all temperature sensitive for this phenotype. Mutations in encore also affect the process of oocyte differentiation. Egg chambers are produced in which the oocyte nucleus has undergone endoreplication often resulting in the formation of 16 nurse cells. We argue that these two phenotypes produced by mutations in encore represent two independent requirements for encore during oogenesis.
在果蝇卵子发生过程中，干细胞的一个子代细胞精确地经历四轮有丝分裂，形成一个由细胞质桥相连的16细胞囊肿。其中一个细胞成为卵母细胞，其余15个细胞分化为滋养细胞。我们鉴定出一个基因encore，它既参与调节生殖系有丝分裂的次数，也参与卵母细胞分化过程。encore基因的突变会导致生殖系中恰好额外进行一轮有丝分裂。遗传学和分子学研究表明，这种有丝分裂缺陷可能是通过基因bag-of-marbles介导的。encore多个等位基因的分离和表征显示，它们对这种表型均为温度敏感型。encore基因的突变也会影响卵母细胞的分化过程。所产生的卵室中，卵母细胞核会进行核内复制，常常导致形成16个滋养细胞。我们认为，encore基因突变产生的这两种表型代表了卵子发生过程中对encore的两种独立需求。
