Abstract
Mutations in supernova, previously shown to uncouple chromosome replication from segregation during cleavage in Drosophila embryos, also sanctions extra divisions of cystoblasts and spermatoblasts. This leads either to the formation of egg chambers which contain more than fifteen nurse cells or testes which have an excess of spermatocytes. In maturing egg chambers two potential oocytes may be specified in which case they are often ectopically located and connected with surrounding nurse cells by four ring canals. However, a typical oocyte nucleus is not always present and these chambers usually become necrotic and degenerate. The nurse cells are of variable size, but are still interconnected by a system of ring canals. They all possess a polyploid nucleus. Sequestering of maternal mRNA's from the nurse cells into the potential oocyte(s) takes place but there is no localization of this maternal information within the oocyte probably because of defective microtubule assembly. Many spermatocytes fail to complete meiosis so that bundles of spermatids are reduced in size and the males have reduced fertility. It is proposed that this gene is indirectly involved in regulating the timing of mitotic divisions in both cystoblasts and spermatoblasts through its interference with microtubule assembly which is consistent with its role during embryogenesis.
