ECM-Regulator timp Is Required for Stem Cell Niche Organization and Cyst Production in the Drosophila Ovary

Matrix metalloproteinase 2 degrades collagen I to regulate ovarian development by association with an insulin-like peptide

The ovary generally undergoes tissue remodeling during larval to pupal transition, which includes membrane degeneration and ovariole growth. At the same time, the hormones produced by insects significantly change during metamorphosis. However, the regulatory mechanism for ovarian development and hormones is not fully understood in insects. Herein, we found that matrix metalloproteinase 2 (MMP2) was highly expressed in the ovarian capsules and ovarioles, and the development was abnormal after knocking out MMP2 in Bombyx mori. The process of abnormal degradation of collagen I due to MMP2 deletion, which resulted in abnormal development of ovarioles and eggs, was analyzed in detail. The proteomics of ovaries in the MMP2-knock out and wild type strains showed a critically significant difference in the expression of a protein, insulin-like peptide (ILP). Additional analysis revealed significant alteration of ILP during ovarian development, and abnormal expression of ILP significantly affected ovarian development in vivo and MMP2 expression in vitro and in vivo. These results showed that MMP2 regulation of ovarian tissue remodeling is closely related to ILP expression. Our study provides new insights into the regulatory mechanism of MMP2 and ovarian development in B. mori.

Microplastic exposure disturbs sleep structure, reduces lifespan, and decreases ovary size in Drosophila melanogaster

The organ-specific toxicity resulting from microplastic (MP) exposure has been extensively explored, particularly concerning the gut, liver, testis, and lung. However, under natural conditions, these effects are not restricted to specific organs or tissues. Investigating whether MP exposure presents a systemic threat to an entire organism, impacting factors such as lifespan, sleep, and fecundity, is essential. In this study, we investigated the effects of dietary exposure to two different doses of MPs (1-5 μm) using the terrestrial model organism Drosophila melanogaster. Results indicated that the particles caused gut damage and remained within the digestive system. Continuous MP exposure significantly shortened the lifespan of adult flies. Even short-term exposure disrupted sleep patterns, increasing the length of daytime sleep episodes. Additionally, one week of MP exposure reduced ovary size, with a trend towards decreased egg-laying in mated females. Although MPs did not penetrate the brain or ovaries, transcriptome analysis revealed altered gene expression in these tissues. In the ovary, Gene Ontology (GO) analysis indicated genotoxic effects impacting inflammation, circadian regulation, and metabolic processes, with significant impacts on extracellular structure-related pathways. In the brain, GO analysis identified changes in pathways associated with proteolysis and carbohydrate metabolism. Overall, this study provides compelling evidence of the systemic negative effects of MP exposure, highlighting the urgent need to address and mitigate environmental MP pollution.

Chondroitin sulfate is required for follicle epithelial integrity and organ shape maintenance in Drosophila

Heparan sulfate (HS) and chondroitin sulfate (CS) are evolutionarily conserved glycosaminoglycans that are found in most animal species, including the genetically tractable model organism Drosophila. In contrast to extensive in vivo studies elucidating co-receptor functions of Drosophila HS proteoglycans (PGs), only a limited number of studies have been conducted for those of CSPGs. To investigate the global function of CS in development, we generated mutants for Chondroitin sulfate synthase (Chsy), which encodes the Drosophila homolog of mammalian chondroitin synthase 1, a crucial CS biosynthetic enzyme. Our characterizations of the Chsy mutants indicated that a fraction survive to adult stage, which allowed us to analyze the morphology of the adult organs. In the ovary, Chsy mutants exhibited altered stiffness of the basement membrane and muscle dysfunction, leading to a gradual degradation of the gross organ structure as mutant animals aged. Our observations show that normal CS function is required for the maintenance of the structural integrity of the ECM and gross organ architecture.

TIMP3 promotes the maintenance of neural stem-progenitor cells in the mouse subventricular zone

Adult neural stem cells (NSCs) in the mouse subventricular zone (SVZ) serve as a lifelong reservoir for newborn olfactory bulb neurons. Recent studies have identified a slowly dividing subpopulation of embryonic neural stem-progenitor cells (NPCs) as the embryonic origin of adult NSCs. Yet, little is known about how these slowly dividing embryonic NPCs are maintained until adulthood while other NPCs are extinguished by the completion of brain development. The extracellular matrix (ECM) is an essential component of stem cell niches and thus a key determinant of stem cell fate. Here we investigated tissue inhibitors of metalloproteinases (TIMPs)-regulators of ECM remodeling-for their potential roles in the establishment of adult NSCs. We found that Timp2, Timp3, and Timp4 were expressed at high levels in slowly dividing NPCs compared to rapidly dividing NPCs. Deletion of TIMP3 reduced the number of adult NSCs and neuroblasts in the lateral SVZ. In addition, overexpression of TIMP3 in the embryonic NPCs suppressed neuronal differentiation and upregulated the expression levels of Notch signaling relating genes. These results thus suggest that TIMP3 keeps the undifferentiated state of embryonic NPCs, leading to the establishment and maintenance of adult NSCs.

Decellularized Extracellular Matrix for Remodeling Bioengineering Organoid's Microenvironment

Over the past decade, stem cell- and tumor-derived organoids are the most promising models in developmental biology and disease modeling, respectively. The matrix is one of three main elements in the construction of an organoid and the most important module of its extracellular microenvironment. However, the source of the currently available commercial matrix, Matrigel, limits the application of organoids in clinical medicine. It is worth investigating whether the original decellularized extracellular matrix (dECM) can be exploited as the matrix of organoids and improving organoid construction are very important. In this review, tissue decellularization protocols and the characteristics of decellularization methods, the mechanical support and biological cues of extraccellular matrix (ECM), methods for construction of multifunctional dECM and responsive dECM hydrogel, and the potential applications of functional dECM are summarized. In addition, some expectations are provided for dECM as the matrix of organoids in clinical applications.

Integrins control epithelial stem cell proliferation in the Drosophila ovary by modulating the Notch pathway

Cell proliferation and differentiation show a remarkable inverse relationship. The temporal coupling between cell cycle withdrawal and differentiation of stem cells (SCs) is crucial for epithelial tissue growth, homeostasis and regeneration. Proliferation vs. differentiation SC decisions are often controlled by the surrounding microenvironment, of which the basement membrane (BM; a specialized form of extracellular matrix surrounding cells and tissues), is one of its main constituents. Years of research have shown that integrin-mediated SC-BM interactions regulate many aspects of SC biology, including the proliferation-to-differentiation switch. However, these studies have also demonstrated that the SC responses to interactions with the BM are extremely diverse and depend on the cell type and state and on the repertoire of BM components and integrins involved. Here, we show that eliminating integrins from the follicle stem cells (FSCs) of the Drosophila ovary and their undifferentiated progeny increases their proliferation capacity. This results in an excess of various differentiated follicle cell types, demonstrating that cell fate determination can occur in the absence of integrins. Because these phenotypes are similar to those found in ovaries with decreased laminin levels, our results point to a role for the integrin-mediated cell-BM interactions in the control of epithelial cell division and subsequent differentiation. Finally, we show that integrins regulate proliferation by restraining the activity of the Notch/Delta pathway during early oogenesis. Our work increases our knowledge of the effects of cell-BM interactions in different SC types and should help improve our understanding of the biology of SCs and exploit their therapeutic potential.

Focal adhesion-mediated cell anchoring and migration: from in vitro to in vivo

Cell-extracellular matrix interactions have been studied extensively using cells cultured in vitro. These studies indicate that focal adhesion (FA)-based cell-extracellular matrix interactions are essential for cell anchoring and cell migration. Whether FAs play a similarly important role in vivo is less clear. Here, we summarize the formation and function of FAs in cultured cells and review how FAs transmit and sense force in vitro. Using examples from animal studies, we also describe the role of FAs in cell anchoring during morphogenetic movements and cell migration in vivo. Finally, we conclude by discussing similarities and differences in how FAs function in vitro and in vivo.

Metalloproteases in gonad formation and ovulation

Changes in expression or activation of various metalloproteases including matrix metalloproteases (Mmp), a disintegrin and metalloprotease (Adam) and a disintegrin and metalloprotease with thrombospondin motif (Adamts), and their endogenous inhibitors (tissue inhibitors of metalloproteases, Timp), have been shown to be critical for ovulation in various species from studies in past decades. Some of these metalloproteases such as Adamts1, Adamts9, Mmp2, and Mmp9 have also been shown to be regulated by luteinizing hormone (LH) and/or progestin, which are essential triggers for ovulation in all vertebrate species. Most of these metalloproteases also express broadly in various tissues and cells including germ cells and somatic gonad cells. Thus, metalloproteases likely play roles in gonad formation processes comprising primordial germ cell (PGC) migration, development of germ and somatic cells, and sex determination. However, our knowledge on the functions and mechanisms of metalloproteases in these processes in vertebrates is still lacking. This review will summarize our current knowledge on the metalloproteases in ovulation and gonad formation with emphasis on PGC migration and germ cell development.

Stem cell niche organization in the Drosophila ovary requires the ECM component Perlecan

Stem cells reside in specialized microenvironments or niches that balance stem cell proliferation and differentiation.^1,2 The extracellular matrix (ECM) is an essential component of most niches, because it controls niche homeostasis, provides physical support, and conveys extracellular signals.3, 4, 5, 6, 7, 8, 9, 10, 11 Basement membranes (BMs) are thin ECM sheets that are constituted mainly by Laminins, Perlecan, Collagen IV, and Entactin/Nidogen and surround epithelia and other tissues.¹² Perlecans are secreted proteoglycans that interact with ECM proteins, ligands, receptors, and growth factors such as FGF, PDGF, VEGF, Hedgehog, and Wingless.13, 14, 15, 16, 17, 18 Thus, Perlecans have structural and signaling functions through the binding, storage, or sequestering of specific ligands. We have used the Drosophila ovary to assess the importance of Perlecan in the functioning of a stem cell niche. Ovarioles in the adult ovary are enveloped by an ECM sheath and possess a tapered structure at their anterior apex termed the germarium. The anterior tip of the germarium hosts the germline niche, where two to four germline stem cells (GSCs) reside together with a few somatic cells: terminal filament cells (TFCs), cap cells (CpCs), and escort cells (ECs).¹⁹ We report that niche architecture in the developing gonad requires trol, that niche cells secrete an isoform-specific Perlecan-rich interstitial matrix, and that DE-cadherin-dependent stem cell-niche adhesion necessitates trol. Hence, we provide evidence to support a structural role for Perlecan in germline niche establishment during larval stages and in the maintenance of a normal pool of stem cells in the adult niche.

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The Drosophila ovarian niche contains a Perlecan-rich interstitial matrix

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Niche cells express and secrete specific Perlecan isoforms

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Absence of trol results in aberrant niches containing fewer niche and stem cells

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trol regulates DE-cadherin levels in larval and adult niche cells

Fibronectin-based nanomechanical biosensors to map 3D surface strains in live cells and tissue

Mechanical forces are integral to cellular migration, differentiation and tissue morphogenesis; however, it has proved challenging to directly measure strain at high spatial resolution with minimal perturbation in living sytems. Here, we fabricate, calibrate, and test a fibronectin (FN)-based nanomechanical biosensor (NMBS) that can be applied to the surface of cells and tissues to measure the magnitude, direction, and strain dynamics from subcellular to tissue length-scales. The NMBS is a fluorescently-labeled, ultra-thin FN lattice-mesh with spatial resolution tailored by adjusting the width and spacing of the lattice from 2-100 µm. Time-lapse 3D confocal imaging of the NMBS demonstrates 2D and 3D surface strain tracking during mechanical deformation of known materials and is validated with finite element modeling. Analysis of the NMBS applied to single cells, cell monolayers, and Drosophila ovarioles highlights the NMBS's ability to dynamically track microscopic tensile and compressive strains across diverse biological systems where forces guide structure and function.

Neuronal octopamine signaling regulates mating-induced germline stem cell increase in female Drosophila melanogaster

Stem cells fuel the development and maintenance of tissues. Many studies have addressed how local signals from neighboring niche cells regulate stem cell identity and their proliferative potential. However, the regulation of stem cells by tissue-extrinsic signals in response to environmental cues remains poorly understood. Here we report that efferent octopaminergic neurons projecting to the ovary are essential for germline stem cell (GSC) increase in response to mating in female Drosophila. The neuronal activity of the octopaminergic neurons is required for mating-induced GSC increase as they relay the mating signal from sex peptide receptor-positive cholinergic neurons. Octopamine and its receptor Oamb are also required for mating-induced GSC increase via intracellular Ca²⁺ signaling. Moreover, we identified Matrix metalloproteinase-2 as a downstream component of the octopamine-Ca²⁺ signaling to induce GSC increase. Our study provides a mechanism describing how neuronal system couples stem cell behavior to environmental cues through stem cell niche signaling.

Metalloproteinases and Their Inhibitors: Potential for the Development of New Therapeutics

The metalloproteinase (MP) family of zinc-dependent proteases, including matrix metalloproteinases (MMPs), a disintegrin and metalloproteases (ADAMs), and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs) plays a crucial role in the extracellular matrix (ECM) remodeling and degradation activities. A wide range of substrates of the MP family includes ECM components, chemokines, cell receptors, and growth factors. Metalloproteinases activities are tightly regulated by proteolytic activation and inhibition via their natural inhibitors, tissue inhibitors of metalloproteinases (TIMPs), and the imbalance of the activation and inhibition is responsible in progression or inhibition of several diseases, e.g., cancer, neurological disorders, and cardiovascular diseases. We provide an overview of the structure, function, and the multifaceted role of MMPs, ADAMs, and TIMPs in several diseases via their cellular functions such as proteolysis of other cell signaling factors, degradation and remodeling of the ECM, and other essential protease-independent interactions in the ECM. The significance of MP inhibitors targeting specific MMP or ADAMs with high selectivity is also discussed. Recent advances and techniques used in developing novel MP inhibitors and MP responsive drug delivery tools are also reviewed.

The expression, purification, and substrate analysis of matrix metalloproteinases in Drosophila melanogaster

Matrix metalloproteinases (MMPs) are evolutionarily conserved extracellular matrix proteinases. Genetic analysis of the Drosophila MMPs, Mmp1 and Mmp2, in vivo reveal that they play vital roles in tissue remodeling. Although the catalytic domain (CD) undertakes most MMP functions, few studies have sought to demonstrate the biochemical properties of the CDs of fly MMPs. Here, we identified the overexpression, purification, and refolding of the CDs of Drosophila Mmp1 and Mmp2 for biochemical studies. Zymography assays and substrate degradation analysis showed that both Mmp1-CD and Mmp2-CD were able to digest casein, gelatin, fibronectin, collagen (types I, IV, and V), while Mmp2-CD showed much higher degradation activity compared with Mmp1-CD. Moreover, human collagen III could be degraded by Mmp1-CD but not Mmp2-CD, and rat collagen I and laminin could be degraded by Mmp2-CD but not Mmp1-CD, suggesting that Drosophila Mmp1 and Mmp2 might have overlapping yet distinct substrate specificity. Using synthetic fluorescent substrates, we further demonstrated that the enzymatic activity of Mmp1-CD and Mmp2-CD could be inhibited by human tissue inhibitors of metalloproteinases (TIMPs). These results reveal the context of the cooperative yet distinct roles of Mmp1 and Mmp2 in tissue remodeling.

Adamts9 is necessary for ovarian development in zebrafish

Expression of adamts9 (A disintegrin and metalloprotease with thrombospondin type-1 motif, member 9) increases dramatically in the somatic cells surrounding oocytes during ovulation in vertebrates from zebrafish to human. However, the function of Adamts9 during ovulation has not been determined due to the embryonic lethality of knockouts in mice and Drosophila. To identify the role of Adamts9 during ovulation we generated knockout (adamts9^-/-) zebrafish using CRISPR/Cas9 and characterized the effects of the mutation. From 1047 fish generated by crossing adamts9^+/- pairs, we found significantly fewer adult adamts9^-/- fish (4%) than predicted by Mendelian ratios (25%). Of the mutants found, there was a significant male bias (82%). Only 3 female mutants were identified (7%), and they had small ovaries with few stage III and IV oocytes compared to wildtype (wt) counterparts of comparable size and age. Astoundingly, the remaining mutants (11%) did not appear to have normal testis or ovaries. Instead there was a pair of transparent, ovarian-like membranous shells that filled the abdominal cavity. Histological examination confirmed that shells were largely empty with no internal structure. Surprisingly, seminiferous tubules and various spermatocytes including mature spermatozoa were observed on the periphery of these transparent shells. No female or female like knockouts were observed to release eggs, and no ovulated oocytes were observed in histological sections. To our knowledge, this is the first report of an adamts9 global knockout model in any adult vertebrates and the first description of how gonadal sex and structure are affected- highlighting the importance of Adamts9 during gonadal development and the value of zebrafish as a model organism.

The Role of Tissue Inhibitors of Metalloproteinases in Organ Development and Regulation of ADAMTS Family Metalloproteinases in Caenorhabditis elegans

Remodeling of the extracellular matrix supports tissue and organ development, by regulating cellular morphology and tissue integrity. However, proper extracellular matrix remodeling requires spatiotemporal regulation of extracellular metalloproteinase activity. Members of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) family, including MIG-17 and GON-1, are evolutionarily conserved, secreted, zinc-requiring metalloproteinases. Although these proteases are required for extracellular matrix remodeling during gonadogenesis in Caenorhabditis elegans, their in vivo regulatory mechanisms remain to be delineated. Therefore, we focused on the C. elegans tissue inhibitors of metalloproteinases (TIMPs), TIMP-1 and CRI-2 Analysis of the transcription and translation products for GFP/Venus fusions, with TIMP-1 or CRI-2, indicated that these inhibitors were secreted and localized to the basement membrane of gonads and the plasma membrane of germ cells. A timp-1 deletion mutant exhibited gonadal growth defects and sterility, and the phenotypes of this mutant were fully rescued by a TIMP-1::Venus construct, but not by a TIMP-1(C21S)::Venus mutant construct, in which the inhibitor coding sequence had been mutated. Moreover, genetic data suggested that TIMP-1 negatively regulates proteolysis of the α1 chain of type IV collagen. We also found that the loss-of-function observed for the mutants timp-1 and cri-2 involves a partial suppression of gonadal defects found for the mutants mig-17/ADAMTS and gon-1/ADAMTS, and that this suppression was canceled upon overexpression of gon-1 or mig-17, respectively. Based on these results, we propose that both TIMP-1 and CRI-2 act as inhibitors of MIG-17 and GON-1 ADAMTSs to regulate gonad development in a noncell-autonomous manner.

Gene expression profiling of ovary identified eggshell proteins regulated by 20-hydroxyecdysone in Bactrocera dorsalis

The oriental fruit fly, Bactrocera dorsalis, is one of the most destructive pests worldwide. The frequent use of chemical insecticides has led B. dorsalis to develop resistance to many insecticides in recent decades. New high-throughput-sequenced transcriptomes, as well as genomes, have revealed a large number of reference genes for functional target identification. Here, we performed digital gene expression profiling of ovary and testis of B. dorsalis adults. Various genes were identified to be highly expressed in B. dorsalis ovary. The genes encoding components of eggshell, vitelline membrane proteins (Vmps) and chorion-related proteins, were identified to be tissue-specifically expressed in ovary. Five cytochrome P450 genes were also identified to be highly expressed in ovary. Three of them were ecdysone synthesis pathway genes indicating the ovary as a potential synthesis site of female. The up-regulated expression of Vmps by exogenous 20-hydroxyecdysone implied the hormonal regulation of eggshell formation during ovarian development. Many other genes with potential functions in ovarian development were also identified, including vitellogenin receptor, insulin receptor, NASP protein, and odorant binding protein. These findings should promote our understanding of the regulation of vitellogenesis and eggshell formation and enable exploration of potentially novel pest control targets.

Morphology of ovary and spermathecae of the parasitoid Eibesfeldtphora tonhascai Brown (Diptera: Phoridae)

Eibesfeldtphora tonhascai (Diptera: Phoridae) is a parasitoid of leaf-cutting ants and a potential biological control agent against these insect pests. This study describes the morphology of the ovary and spermatheca of E. tonhascai. The female reproductive tract of this parasitoid has a pair of meroistic polytrophic ovaries, two lateral oviducts that open into a common oviduct, an elongated accessory gland, and two spermathecae. Young oocytes are small and spherical, and their size increases as yolk is stored in the cytoplasm. This process is followed by chorion production by follicular cells. Mature oocytes are elliptical or torpedo-shaped. The reservoir wall of the spermatheca has type III glandular cells with cytoplasm rich in free ribosomes, rough endoplasmic reticulum, and secretory vesicles. The apical surface of these cells has microvilli associated with mitochondria. The reservoir lumen is lined by a cuticle and filled with spermatozoa. This is the first report of the ovary and spermatheca morphology of E. tonhascai and contributes to the comprehension of the reproductive biology of this parasitoid of leaf-cutting ants.

Multiple Pools of Nuclear Actin

While nuclear actin was reported ~50 years ago, it's in vivo prevalence and structure remain largely unknown. Here, we use Drosophila oogenesis, that is, follicle development, to characterize nuclear actin. We find that three different reagents-DNase I, anti-actin C4, and anti-actin AC15-recognize distinct pools of nuclear actin. DNase I labels monomeric or G-actin, and, during follicle development, G-actin is present in the nucleus of every cell. Some G-actin is recognized by the C4 antibody. In particular, C4 nuclear actin colocalizes with DNase I to the nucleolus in anterior escort cells, follicle stem cells, some mitotic follicle cells, and a subset of nurse cells during early oogenesis. C4 also labels polymeric nuclear actin in the nucleoplasm of the germline stem cells, early cystoblasts, and oocytes. The AC15 antibody labels a completely distinct pool of nuclear actin from that of DNase I and C4. Specifically, AC15 nuclear actin localizes to the chromatin in the nurse and follicle cells during mid-to-late oogenesis. Within the oocyte, AC15 nuclear actin progresses from localizing to puncta surrounding the DNA, to forming a filamentous cage around the chromosomes. Together these findings reveal that nuclear actin is highly prevalent in vivo, and multiple pools of nuclear actin exist and can be recognized using different reagents. Additionally, our localization studies suggest that nuclear actin may regulate stemness, nucleolar structure and function, transcription, and nuclear structure. Such findings call for further studies to explore the prevalence, diversity, and functions of nuclear actin across tissues and organisms. Anat Rec, 301:2014-2036, 2018. © 2018 Wiley Periodicals, Inc.

De novo transcriptome analysis to search for sex-differentiation genes in the Siberian sturgeon

The sturgeon family includes many species that are lucrative for commercial caviar production, some of which face critical conservation problems. The purpose of this study was to identify genes involved in gonadal sex differentiation in sturgeons, contributing to our understanding of the biological cycle of this valuable species. A high-quality de novo Siberian sturgeon gonadal transcriptome was built for this study using gonadal samples from undifferentiated fish at 3, 5, and 6 months of age; recently sex-differentiated fish at 9 months of age; and immature males and females at 14-17 months of age. Undifferentiated fish were sexed after validation of forkhead box L2 (foxl2) and cytochrome P450, family 19, subfamily A, and polypeptide 1a (cyp19a1a) as sex markers, and the transcriptomes of the 3-month-old undifferentiated fish, 5-6-month-old future females, and 5-6-month-old putative males were compared. The ovarian program was associated with strong activation of genes involved in estrogen synthesis (cyp19a1, foxl2, and estradiol 17-beta-dehydrogenase 1), stem-cell niche building and regulation, and sex-specific nerve cell development. The genes related to the stem-cell niche were: (1) the family of iroquois-class homeodomain proteins 3, 4, and 5 (irx3, irx4, irx5-1, irx5-2, and irx5-3), which are essential for somatic-germ cell interaction; (2) extracellular matrix remodeling genes, such as collagen type XXVIII alpha 1 chain and collagen type II alpha 1 chain, matrix metalloproteinases 24-1 and 24-2, and NADPH oxidase organizer 1, which, along with the somatic cells, provide architectural support for the stem-cell niche; and (3) mitogenic factors, such as lim homeobox 2, amphiregulin, G2/M phase-specific E3 ubiquitin-protein ligase, and connector enhancer of kinase suppressor of ras 2, which are up regulated in conjunction with the anti-apoptotic gene G2/M phase-specific E3 ubiquitin-protein ligase suggesting a potential involvement in regulating the number of germ cells. Genes related to sex-specific nerve cell developments were: the neurofilament medium polypeptides, the gene coding for serotonin receptor 7, 5-hydroxytryptamine receptor 7; neurotensin, isoform CRA-a, the neuron-specific transmembrane protein Delta/Notch-like epidermal growth factor-related receptor; and insulinoma-associated protein 1. The putative testicular program was poorly characterized by elements of the immune response. The classic markers of maleness were not specifically activated, indicating that testicular differentiation occurs at a later stage. In sum, the ovarian program, but not the testicular program, is in place by 5-6 months of age in the Siberian sturgeon. The female program is characterized by estrogen-related genes with well-established roles in gonadal differentiation, but also by several genes with no previously-described function in the ovarian development of fish. These newly-reported genes are involved in stem-cell niche building and regulation as well as sex-specific nerve development.

Research advances in the regulation of the putative ovarian germline stem cell niche on female germline stem cells

Stem cells are ideal seeding cells, which have the potential for self-renewal and multiple differentiation, and they play a fundamental role in maintaining homeostasis and regenerating and repairing tissue. The discovery of female germline stem cells (FGSCs) brings much hope for the postnatal renewal of oocytes and solving some female infertility problems. Ovarian function declines with increasing female age. Moreover, ovarian germline stem cell niche-aging could be the main cause of ovarian senescence, which ultimately leads to decreased follicle generation, declining female fertility, and age-related diseases, such as osteoporosis and ovarian cancer. The ovarian germline stem cell niche is the surrounding microenvironment in which FGSCs live, and it helps control the biological characteristics of FGSCs in many ways, such as nutritional supply and immunological cytokine secretion. This paper reviews the knowledge about the ovarian germline stem cell niche and its probable regulatory mechanisms on FGSCs, which provides valuable scientific information and scope for the prevention and treatment of ovarian senescence. Abbreviations: BMP: bone morphogenetic protein; Dpp: decapentaplegic; FGSC: female germline stem cell; IL, interleukin; OGSC: ovarian germline stem cells; ROS: reactive oxygen species; TGF, transforming growth factor; TNF, tumor necrosis factor.

JAK/STAT signaling prevents excessive apoptosis to ensure maintenance of the interfollicular stalk critical for Drosophila oogenesis

Apoptosis not only eliminates cells that are damaged or dangerous but also cells whose function during development in patterning or organogenesis is complete. The successful formation of germ cells is essential for the perpetuation of a species. The production of an oocyte often depends on signaling between germline and somatic cells, but also between specialized types of somatic cells. In Drosophila, each developing egg chamber is separated from the next by a single file of interfollicular somatic cells. Little is known about the function of the interfollicular stalk, although its presumed role in separating egg chambers is to ensure that patterning cues from one egg chamber do not impact or disrupt the development of adjacent egg chambers. We found that cells comprising the stalk undergo a progressive decrease in number during oogenesis through an apoptotic-dependent loss. The extent of programmed cell death is restricted by JAK/STAT signaling in a cell-autonomous manner to ensure that the stalk is maintained. Both a failure to undergo the normal reduction in stalk cell number, or to prevent excessive stalk cell apoptosis results in a decrease in fecundity. Thus, activation of JAK/STAT signaling in the Drosophila interfollicular stalk emerges as a model to study the tight regulation of signaling-dependent apoptosis.

Juvenile hormone and 20-hydroxyecdysone coordinately control the developmental timing of matrix metalloproteinase-induced fat body cell dissociation

Tissue remodeling is a crucial process in animal development and disease progression. Coordinately controlled by the two main insect hormones, juvenile hormone (JH) and 20-hydroxyecdysone (20E), tissues are remodeled context-specifically during insect metamorphosis. We previously discovered that two matrix metalloproteinases (Mmps) cooperatively induce fat body cell dissociation in Drosophila However, the molecular events involved in this Mmp-mediated dissociation are unclear. Here we report that JH and 20E coordinately and precisely control the developmental timing of Mmp-induced fat body cell dissociation. We found that during the larval-prepupal transition, the anti-metamorphic factor Kr-h1 transduces JH signaling, which directly inhibited Mmp expression and activated expression of tissue inhibitor of metalloproteinases (timp) and thereby suppressed Mmp-induced fat body cell dissociation. We also noted that upon a decline in the JH titer, a prepupal peak of 20E suppresses Mmp-induced fat body cell dissociation through the 20E primary-response genes, E75 and Blimp-1, which inhibited expression of the nuclear receptor and competence factor βftz-F1 Moreover, upon a decline in the 20E titer, βftz-F1 expression was induced by the 20E early-late response gene DHR3, and then βftz-F1 directly activated Mmp expression and inhibited timp expression, causing Mmp-induced fat body cell dissociation during 6-12 h after puparium formation. In conclusion, coordinated signaling via JH and 20E finely tunes the developmental timing of Mmp-induced fat body cell dissociation. Our findings shed critical light on hormonal regulation of insect metamorphosis.

Variations in basement membrane mechanics are linked to epithelial morphogenesis

The regulation of morphogenesis by the basement membrane (BM) may rely on changes in its mechanical properties. To test this, we developed an atomic force microscopy-based method to measure BM mechanical stiffness during two key processes in Drosophila ovarian follicle development. First, follicle elongation depends on epithelial cells that collectively migrate, secreting BM fibrils perpendicularly to the anteroposterior axis. Our data show that BM stiffness increases during this migration and that fibril incorporation enhances BM stiffness. In addition, stiffness heterogeneity, due to oriented fibrils, is important for egg elongation. Second, epithelial cells change their shape from cuboidal to either squamous or columnar. We prove that BM softens around the squamous cells and that this softening depends on the TGFβ pathway. We also demonstrate that interactions between BM constituents are necessary for cell flattening. Altogether, these results show that BM mechanical properties are modified during development and that, in turn, such mechanical modifications influence both cell and tissue shapes.

The repertoire of epithelial morphogenesis on display: Progressive elaboration of Drosophila egg structure

Epithelial structures are foundational for tissue organization in all metazoans. Sheets of epithelial cells form lateral adhesive junctions and acquire apico-basal polarity perpendicular to the surface of the sheet. Genetic analyses in the insect model, Drosophila melanogaster, have greatly advanced our understanding of how epithelial organization is established, and how it is modulated during tissue morphogenesis. Major insights into collective cell migrations have come from analyses of morphogenetic movements within the adult follicular epithelium that cooperates with female germ cells to build a mature egg. Epithelial follicle cells progress through tightly choreographed phases of proliferation, patterning, reorganization and migrations, before they differentiate to form the elaborate structures of the eggshell. Distinct structural domains are organized by differential adhesion, within which lateral junctions are remodeled to further shape the organized epithelia. During collective cell migrations, adhesive interactions mediate supracellular organization of planar polarized macromolecules, and facilitate crawling over the basement membrane or traction against adjacent cell surfaces. Comparative studies with other insects are revealing the diversification of morphogenetic movements for elaboration of epithelial structures. This review surveys the repertoire of follicle cell morphogenesis, to highlight the coordination of epithelial plasticity with progressive differentiation of a secretory epithelium. Technological advances will keep this tissue at the leading edge for interrogating the precise spatiotemporal regulation of normal epithelial reorganization events, and provide a framework for understanding pathological tissue dysplasia.

TIMPs: versatile extracellular regulators in cancer

A compelling long-term goal of cancer biology is to understand the crucial players during tumorigenesis in order to develop new interventions. Here, we review how the four non-redundant tissue inhibitors of metalloproteinases (TIMPs) regulate the pericellular proteolysis of a vast range of matrix and cell surface proteins, generating simultaneous effects on tumour architecture and cell signalling. Experimental studies demonstrate the contribution of TIMPs to the majority of cancer hallmarks, and human cancers invariably show TIMP deregulation in the tumour or stroma. Of the four TIMPs, TIMP1 overexpression or TIMP3 silencing is consistently associated with cancer progression or poor patient prognosis. Future efforts will align mouse model systems with changes in TIMPs in patients, will delineate protease-independent TIMP function, will pinpoint therapeutic targets within the TIMP-metalloproteinase-substrate network and will use TIMPs in liquid biopsy samples as biomarkers for cancer prognosis.

Minireview: Syndecans and their crucial roles during tissue regeneration

Syndecans are transmembrane heparan sulfate proteoglycans, with roles in development, tumorigenesis and inflammation, and growing evidence for involvement in tissue regeneration. This is a fast developing field with the prospect of utilizing tissue engineering and biomaterials in novel therapies. Syndecan receptors are not only ubiquitous in mammalian tissues, regulating cell adhesion, migration, proliferation, and differentiation through independent signaling but also working alongside other receptors. Their importance is highlighted by an ability to interact with a diverse array of ligands, including extracellular matrix glycoproteins, growth factors, morphogens, and cytokines that are important regulators of regeneration. We also discuss the potential for syndecans to regulate stem cell properties, and suggest that understanding these proteoglycans is relevant to exploiting cell, tissue, and materials technologies.