NR5A Nuclear Receptor Hr39 Controls Three-Cell Secretory Unit Formation in Drosophila Female Reproductive Glands

SummaryBackgroundSecretions within the adult female reproductive tract mediate sperm survival, storage, activation, and selection. Drosophila female reproductive gland secretory cells reside within the adult spermathecae and parovaria, but their development remains poorly characterized.ResultsWith cell-lineage tracing, we found that precursor cells downregulate lozenge and divide stereotypically to generate three-cell secretory units during pupal development. The NR5A-class nuclear hormone receptor Hr39 is essential for precursor cell division and secretory unit formation. Moreover, ectopic Hr39 in multiple tissues generates reproductive gland-like primordia. Rarely, in male genital discs these primordia can develop into sperm-filled testicular spermathecae.ConclusionDrosophila spermathecae provide a powerful model for studying gland development. Hr39 functions as a master regulator of a program that may have been conserved throughout animal evolution for the production of female reproductive glands and other secretory tissues

Searching Chromatin for Stem Cell Identity

Stem cells encapsulate the fundamental problem of metazoan biology in miniature: How do cells establish and maintain their fates? Increasing evidence indicates that stem cell chromatin activates proliferation genes and represses differentiation genes. Understanding how these configurations are stabilized by Polycomb group proteins will advance our understanding of embryonic development, tissue homeostasis, regeneration, aging, and oncogenesis

Stem Cells and Niches: Mechanisms That Promote Stem Cell Maintenance throughout Life

Niches are local tissue microenvironments that maintain and regulate stem cells. Long-predicted from mammalian studies, these structures have recently been characterized within several invertebrate tissues using methods that reliably identify individual stem cells and their functional requirements. Although similar single-cell resolution has usually not been achieved in mammalian tissues, principles likely to govern the behavior of niches in diverse organisms are emerging. Considerable progress has been made in elucidating how the microenvironment promotes stem cell maintenance. Mechanisms of stem cell maintenance are key to the regulation of homeostasis and likely contribute to aging and tumorigenesis when altered during adulthood

The expression profile of purified Drosophila germline stem cells

AbstractWe developed a method to highly purify germline stem cells (GSCs) from the Drosophila ovary, one of the best understood types of adult stem cell. GSCs express variant isoforms of general transcriptional components, translation initiation factors, and several variant ribosomal proteins, including RpL22, a protein enriched in several mammalian stem cells. These novel isoforms may help regulate stem cell gene expression because a reversion assay indicated that at least four were specific for GSCs. By comparative analysis, we identify additional genes enriched in GSCs, including Psc, the Drosophila homolog of the Bmi-1 Polycomb group gene, as well as genes that may delay cytokinesis in pre-meiotic germ cells. By comparing GSCs arrested by BMP over-expression and bam mutation, we hypothesize that mRNA utilization is modulated in differentiating GSC daughters. Our findings suggest that Drosophila and mammalian stem cells utilize at least two regulatory mechanisms in common

Drosophila Eggshell Production: Identification of New Genes and Coordination by Pxt

Drosophila ovarian follicles complete development using a spatially and temporally controlled maturation process in which they resume meiosis and secrete a multi-layered, protective eggshell before undergoing arrest and/or ovulation. Microarray analysis revealed more than 150 genes that are expressed in a stage-specific manner during the last 24 hours of follicle development. These include all 30 previously known eggshell genes, as well as 19 new candidate chorion genes and 100 other genes likely to participate in maturation. Mutations in pxt, encoding a putative Drosophila cyclooxygenase, cause many transcripts to begin expression prematurely, and are associated with eggshell defects. Somatic activity of Pxt is required, as RNAi knockdown of pxt in the follicle cells recapitulates both the temporal expression and eggshell defects. One of the temporally regulated genes, cyp18a1, which encodes a cytochromome P450 protein mediating ecdysone turnover, is downregulated in pxt mutant follicles, and cyp18a1 mutation itself alters eggshell gene expression. These studies further define the molecular program of Drosophila follicle maturation and support the idea that it is coordinated by lipid and steroid hormonal signals

The Drosophila P68 RNA helicase regulates transcriptional deactivation by promoting RNA release from chromatin

Terminating a gene’s activity requires that pre-existing transcripts be matured or destroyed and that the local chromatin structure be returned to an inactive configuration. Here we show that the Drosophila homolog of the mammalian P68 RNA helicase plays a novel role in RNA export and gene deactivation. p68 mutations phenotypically resemble mutations in small bristles (sbr), the Drosophila homolog of the human mRNA export factor NXF1. Full-length hsp70 mRNA accumulates in the nucleus near its sites of transcription following heat shock of p68 homozygotes, and hsp70 gene shutdown is delayed. Unstressed mutant larvae show similar defects in transcript accumulation and gene repression at diverse loci, and we find that p68 mutations are allelic to Lighten-up, a known suppressor of position effect variegation. Our observations reveal a strong connection between transcript clearance and gene repression. P68 may be needed to rapidly remove transcripts from a gene before its activity can be shut down and its chromatin reset to an inactive state