ASYMMETRIC SEGREGATION OF THE HOMEODOMAIN PROTEIN PROSPERO DURING DROSOPHILA DEVELOPMENT

ASYMMETRIC divisions that produce two distinct cells play fundamental roles in generating different cell types during development(1,2). In t he Drosophila central nervous system, neural stem cells called neurobl asts divide unequally into another neuroblast and a ganglion mother ce ll which is Subsequently cleaved into neurons. Correct gene expression of ganglion mother tells requires the transcription factor Prospero(3 -5). Here we demonstrate the asymmetric segregation of Prospero on neu roblast division, Prospero synthesized in neuroblasts is retained in t he cytoplasm and at mitosis is exclusively partitioned to ganglion mot her cells, in which it is translocated to the nucleus, Differential se gregation of Prospero was also found in the endoderm. We have identifi ed a region in Prospero that is responsible for this event, The region shares a common motif with Numb(6), which also shows unequal segregat ion(7). We propose that asymmetric segregation of transcription factor s is an intrinsic mechanism for establishing asymmetry in gene express ion between sibling cells.