Bradysia (Sciara) coprophila larvae up-regulate DNA repair pathways and down-regulate developmental regulators in response to ionizing radiation.

The level of resistance to radiation and the developmental and molecular responses can vary between species, and even between developmental stages of one species. For flies (order: Diptera), prior studies concluded that the fungus gnat Bradysia (Sciara) coprophila (sub-order: Nematocera) is more resistant to irradiation-induced mutations that cause visible phenotypes than the fruit fly Drosophila melanogaster (sub-order: Brachycera). Therefore, we characterized the effects of and level of resistance to ionizing radiation on B.

Recent Evolution of a Maternally Acting Sex-Determining Supergene in a Fly with Single-Sex Broods.

Sex determination is a key developmental process, yet it is remarkably variable across the tree of life. The dipteran family Sciaridae exhibits one of the most unusual sex determination systems in which mothers control offspring sex through selective elimination of paternal X chromosomes. Whereas in some members of the family females produce mixed-sex broods, others such as the dark-winged fungus gnat Bradysia coprophila are monogenic, with females producing single-sex broods.

Aliens in the CYPome of the black fungus gnat, Bradysia coprophila.

The diverse cytochrome P450 enzymes of insects play essential physiological roles and also play important roles in the metabolism of environmental chemicals such as insecticides. We manually curated the complement of P450 (CYP) genes, or CYPome, of the black fungus gnat, Bradysia (Sciara) coprophila (Diptera, Sciaroidea), a species with a variable number of chromosomes. This CYPome carries two types of "alien" P450 genes.

FMRP-dependent production of large dosage-sensitive proteins is highly conserved.

Mutations in FMR1 are the most common heritable cause of autism spectrum disorder. FMR1 encodes an RNA-binding protein, FMRP, which binds to long, autism-relevant transcripts and is essential for normal neuronal and ovarian development. In contrast to the prevailing model that FMRP acts to block translation elongation, we previously found that FMRP activates the translation initiation of large proteins in Drosophila oocytes.

Mouse oocytes develop in cysts with the help of nurse cells.

Mouse germline cysts, on average, develop into six oocytes supported by 24 nurse cells that transfer cytoplasm and organelles to generate a Balbiani body. We showed that between E14.5 and P5, cysts periodically activate some nurse cells to begin cytoplasmic transfer, which causes them to shrink and turnover within 2 days.

High contiguity de novo genome assembly and DNA modification analyses for the fungus fly, Sciara coprophila, using single-molecule sequencing.

Background: The lower Dipteran fungus fly, Sciara coprophila, has many unique biological features that challenge the rule of genome DNA constancy. For example, Sciara undergoes paternal chromosome elimination and maternal X chromosome nondisjunction during spermatogenesis, paternal X elimination during embryogenesis, intrachromosomal DNA amplification of DNA puff loci during larval development, and germline-limited chromosome elimination from all somatic cells. Paternal chromosome elimination in Sciara was the first observation of imprinting, though the mechanism remains a mystery.

Differentiating female germ cells initiate Polycomb silencing by regulating PRC2-interacting proteins.

Polycomb silencing represses gene expression and provides a molecular memory of chromatin state that is essential for animal development. We show that female germline stem cells (GSCs) provide a powerful system for studying Polycomb silencing. GSCs have a non-canonical distribution of PRC2 activity and lack silenced chromatin like embryonic progenitors.

An abundant quiescent stem cell population in Malpighian tubules protects principal cells from kidney stones.

Adult Malpighian tubules have low rates of cell turnover but are vulnerable to damage caused by stones, like their mammalian counterparts, kidneys. We show that renal stem cells (RSCs) in the ureter and lower tubules comprise a unique, unipotent regenerative compartment. RSCs respond only to loss of nearby principal cells (PCs), cells critical for maintaining ionic balance.

Prolonged ovarian storage of mature oocytes dramatically increases meiotic spindle instability.

Human oocytes frequently generate aneuploid embryos that subsequently miscarry. In contrast, oocytes from outbred laboratory stocks develop fully regardless of maternal age. Since mature oocytes are not extensively stored in the ovary under laboratory conditions like they are in the wild, we developed a system to investigate how storage affects oocyte quality.

Dietary Lipids Modulate Notch Signaling and Influence Adult Intestinal Development and Metabolism in Drosophila.

Tissue homeostasis involves a complex balance of developmental signals and environmental cues that dictate stem cell function. We found that dietary lipids control enteroendocrine cell production from Drosophila posterior midgut stem cells. Dietary cholesterol influences new intestinal cell differentiation in an Hr96-dependent manner by altering the level and duration of Notch signaling.

Fragile X mental retardation 1 gene enhances the translation of large autism-related proteins.

Mutations in the fragile X mental retardation 1 gene () cause the most common inherited human autism spectrum disorder. FMR1 influences messenger RNA (mRNA) translation, but identifying functional targets has been difficult. We analyzed quiescent oocytes, which, like neural synapses, depend heavily on translating stored mRNA.

Identification of Genes Mediating Drosophila Follicle Cell Progenitor Differentiation by Screening for Modifiers of GAL4::UAS Variegation.

The Drosophila melanogaster ovarian follicle cell lineage provides a powerful system for investigating how epigenetic changes contribute to differentiation. Downstream from an epithelial stem cell, follicle progenitors undergo nine mitotic cell cycles before transitioning to the endocycle and initiating differentiation. During their proliferative phase, follicle progenitors experience Lsd1-dependent changes in epigenetic stability that can be monitored using GAL4::UAS variegation.

Mouse oocytes differentiate through organelle enrichment from sister cyst germ cells.

Oocytes differentiate in diverse species by receiving organelles and cytoplasm from sister germ cells while joined in germline cysts or syncytia. Mouse primordial germ cells form germline cysts, but the role of cysts in oogenesis is unknown. We find that mouse germ cells receive organelles from neighboring cyst cells and build a Balbiani body to become oocytes, whereas nurselike germ cells die.

Matrix metalloproteinase 2 is required for ovulation and corpus luteum formation in Drosophila.

Ovulation is critical for successful reproduction and correlates with ovarian cancer risk, yet genetic studies of ovulation have been limited. It has long been thought that the mechanism controlling ovulation is highly divergent due to speciation and fast evolution. Using genetic tools available in Drosophila, we now report that ovulation in Drosophila strongly resembles mammalian ovulation at both the cellular and molecular levels.

The progenitor state is maintained by lysine-specific demethylase 1-mediated epigenetic plasticity during Drosophila follicle cell development.

Progenitors are early lineage cells that proliferate before the onset of terminal differentiation. Although widespread, the epigenetic mechanisms that control the progenitor state and the onset of differentiation remain elusive. By studying Drosophila ovarian follicle cell progenitors, we identified lysine-specific demethylase 1 (lsd1) and CoRest as differentiation regulators using a GAL4∷GFP variegation assay.

Female mice lack adult germ-line stem cells but sustain oogenesis using stable primordial follicles.

Whether or not mammalian females generate new oocytes during adulthood from germ-line stem cells to sustain the ovarian follicle pool has recently generated controversy. We used a sensitive lineage-labeling system to determine whether stem cells are needed in female adult mice to compensate for follicular losses and to directly identify active germ-line stem cells. Primordial follicles generated during fetal life are highly stable, with a half-life during adulthood of 10 mo, and thus are sufficient to sustain adult oogenesis without a source of renewal.

Mouse primordial germ cells produce cysts that partially fragment prior to meiosis.

Mammalian germ cells divide mitotically and form nests of associated cells just prior to entering meiosis. At least some nests contain germline cysts that arise by synchronous, incomplete mitotic divisions, but others may form by aggregation. To systematically investigate early murine germ cell development, we lineage marked the progeny of individual, newly arrived primordial germ cells in the E10.

Making the cut: intramembrane cleavage by a rhomboid protease promotes ERAD.

Endoplasmic reticulum–associated degradation (ERAD) is a cellular protein quality-control process that disposes of proteasomal substrates from the early secretory pathway. Recent work shows that the endoplasmic reticulum–resident rhomboid protease RHBDL4 facilitates ERAD by recognizing and cleaving integral membrane substrates. The work indicates that intramembrane proteolysis may have a general role in the extraction of misfolded membrane proteins from the endoplasmic reticulum.

NR5A nuclear receptor Hr39 controls three-cell secretory unit formation in Drosophila female reproductive glands.

Background: Secretions 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.

Results: With cell-lineage tracing, we found that precursor cells downregulate lozenge and divide stereotypically to generate three-cell secretory units during pupal development.

Germline stem cells.

Sperm and egg production requires a robust stem cell system that balances self-renewal with differentiation. Self-renewal at the expense of differentiation can cause tumorigenesis, whereas differentiation at the expense of self-renewal can cause germ cell depletion and infertility. In most organisms, and sometimes in both sexes, germline stem cells (GSCs) often reside in a defined anatomical niche.

Drosophila stem cell niches: a decade of discovery suggests a unified view of stem cell regulation.

The past decade of research on Drosophila stem cells and niches has provided key insights. Fly stem cells do not occupy a special "state" based on novel "stem cell genes" but resemble transiently arrested tissue progenitors. Moreover, individual stem cells and downstream progenitors are highly dynamic and dispensable, not tissue bulwarks.

Error-prone polyploid mitosis during normal Drosophila development.

Endopolyploidy arises during normal development in many species when cells undergo endocycles-variant cell cycles in which DNA replicates but daughter cells do not form. Normally, polyploid cells do not divide mitotically after initiating endocycles; hence, little is known about their mitotic competence. However, polyploid cells are found in many tumors, and the enhanced chromosomal instability of polyploid cells in culture suggests that such cells contribute to tumor aneuploidy.

Epigenetic stability increases extensively during Drosophila follicle stem cell differentiation.

Stem and embryonic cells facilitate programming toward multiple daughter cell fates, whereas differentiated cells resist reprogramming and oncogenic transformation. How alterations in the chromatin-based machinery of epigenetic inheritance contribute to these differences remains poorly known. We observed random, heritable changes in GAL4/UAS transgene programming during Drosophila ovarian follicle stem cell differentiation and used them to measure the stage-specific epigenetic stability of gene programming.