RESUMO
Obesity is linked to reduced fertility in various species, from Drosophila to humans. Considering that obesity is often induced by changes in diet or eating behavior, it remains unclear whether obesity, diet, or both reduce fertility. Here, we show that Drosophila females on a high-sugar diet become rapidly obese and less fertile as a result of increased death of early germline cysts and vitellogenic egg chambers (or follicles). They also have high glycogen, glucose and trehalose levels and develop insulin resistance in their fat bodies (but not ovaries). By contrast, females with adipocyte-specific knockdown of the anti-obesity genes brummer or adipose are obese but have normal fertility. Remarkably, females on a high-sugar diet supplemented with a separate source of water have mostly normal fertility and glucose levels, despite persistent obesity, high glycogen and trehalose levels, and fat body insulin resistance. These findings demonstrate that a high-sugar diet affects specific processes in oogenesis independently of insulin resistance, that high glucose levels correlate with reduced fertility on a high-sugar diet, and that obesity alone does not impair fertility.
Assuntos
Drosophila melanogaster , Resistência à Insulina , Animais , Humanos , Feminino , Drosophila melanogaster/genética , Trealose , Obesidade/etiologia , Dieta , Drosophila , Fertilidade , Glucose , GlicogênioRESUMO
Despite their medical and economic relevance, it remains largely unknown how suboptimal temperatures affect adult insect reproduction. Here, we report an in-depth analysis of how chronic adult exposure to suboptimal temperatures affects oogenesis using the model insect Drosophila melanogaster. In adult females maintained at 18°C (cold) or 29°C (warm), relative to females at the 25°C control temperature, egg production was reduced through distinct cellular mechanisms. Chronic 18°C exposure improved germline stem cell maintenance, survival of early germline cysts and oocyte quality, but reduced follicle growth with no obvious effect on vitellogenesis. By contrast, in females at 29°C, germline stem cell numbers and follicle growth were similar to those at 25°C, while early germline cyst death and degeneration of vitellogenic follicles were markedly increased and oocyte quality plummeted over time. Finally, we also show that these effects are largely independent of diet, male factors or canonical temperature sensors. These findings are relevant not only to cold-blooded organisms, which have limited thermoregulation, but also potentially to warm-blooded organisms, which are susceptible to hypothermia, heatstroke and fever.
Assuntos
Linhagem da Célula/fisiologia , Drosophila melanogaster/fisiologia , Células Germinativas/fisiologia , Oogênese/fisiologia , Células-Tronco/fisiologia , Animais , Temperatura Baixa , Feminino , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Masculino , Oócitos/fisiologia , Folículo Ovariano/fisiologia , Ovário/fisiologia , Transdução de Sinais/fisiologia , Vitelogênese/fisiologiaRESUMO
The conserved nuclear receptor superfamily has crucial roles in many processes, including reproduction. Nuclear receptors with known roles in oogenesis have been studied mostly in the context of their ovary-intrinsic requirement. Recent studies in Drosophila, however, have begun to reveal new roles of nuclear receptor signaling in peripheral tissues in controlling reproduction. Here, we identified Hormone receptor 4 (Hr4) as an oogenesis regulator required in the ovary and muscles. Global Hr4 knockdown leads to increased germline stem cell (GSC) loss, reduced GSC proliferation, early germline cyst death, slowed follicle growth and vitellogenic follicle degeneration. Tissue-specific knockdown experiments uncovered ovary-intrinsic and peripheral tissue requirements for Hr4 In the ovary, Hr4 is required in the niche for GSC proliferation and in the germline for GSC maintenance. Hr4 functions in muscles to promote GSC maintenance and follicle growth. The specific tissues that require Hr4 for survival of early germline cysts and vitellogenic follicles remain unidentified. These results add to the few examples of muscles controlling gametogenesis and expand our understanding of the complexity of nuclear receptor regulation of various aspects of oogenesis.
Assuntos
Proteínas de Drosophila/metabolismo , Drosophila/metabolismo , Músculos/metabolismo , Oogênese/genética , Ovário/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Animais , Animais Geneticamente Modificados/metabolismo , Proliferação de Células , Drosophila/crescimento & desenvolvimento , Proteínas de Drosophila/antagonistas & inibidores , Proteínas de Drosophila/genética , Feminino , Células Germinativas/citologia , Células Germinativas/metabolismo , Músculos/citologia , Folículo Ovariano/crescimento & desenvolvimento , Folículo Ovariano/metabolismo , Ovário/citologia , Óvulo/crescimento & desenvolvimento , Óvulo/metabolismo , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Receptores Citoplasmáticos e Nucleares/antagonistas & inibidores , Receptores Citoplasmáticos e Nucleares/genéticaRESUMO
Developmental biologists have frequently pushed the frontiers of modern biomedical research. From the discovery and characterization of novel signal transduction pathways to exploring the molecular underpinnings of genetic inheritance, transcription, the cell cycle, cell death and stem cell biology, studies of metazoan development have historically opened new fields of study and consistently revealed previously unforeseen avenues of clinical therapies. From this perspective, it is not surprising that our community is now an integral part of the current renaissance in metabolic research. Amidst the global rise in metabolic syndrome, the discovery of novel signaling roles for metabolites, and the increasing links between altered metabolism and many human diseases, we as developmental biologists can contribute skills and expertise that are uniquely suited for investigating the mechanisms underpinning human metabolic health and disease. Here, we summarize the opportunities and challenges that our community faces, and discuss how developmental biologists can make unique and valuable contributions to the field of metabolism and physiology.
Assuntos
Biologia do Desenvolvimento , Doenças Metabólicas/metabolismo , Animais , Drosophila/crescimento & desenvolvimento , Drosophila/metabolismo , Humanos , Doenças Metabólicas/patologia , Neoplasias/metabolismo , Neoplasias/patologia , Oogênese , Ouriços-do-Mar/crescimento & desenvolvimento , Ouriços-do-Mar/metabolismo , Transdução de SinaisRESUMO
Reproduction is intimately linked to the physiology of an organism. Nuclear receptors are widely expressed transcription factors that mediate the effects of many circulating molecules on physiology and reproduction. While multiple studies have focused on the roles of nuclear receptors intrinsically in the ovary, it remains largely unknown how the actions of nuclear receptors in peripheral tissues influence oogenesis. We identified the nuclear receptor encoded by svp as a novel regulator of oogenesis in adult Drosophila. Global somatic knockdown of svp reduces egg production by increasing GSC loss, death of early germline cysts, and degeneration of vitellogenic follicles. Tissue-specific knockdown experiments revealed that svp remotely controls these different steps of oogenesis through separate mechanisms involving distinct tissues. Specifically, adipocyte-specific svp knockdown impairs GSC maintenance and early germline cyst survival, whereas oenocyte-specific svp knockdown increases the death of vitellogenic follicles without any effects on GSCs or early cysts. These results illustrate that nuclear receptors can control reproduction through a variety of mechanisms involving peripheral tissues.
Assuntos
Adipócitos/metabolismo , Proteínas de Ligação a DNA/metabolismo , Oogênese/fisiologia , Receptores de Esteroides/metabolismo , Adipócitos/fisiologia , Animais , Proteínas de Ligação a DNA/fisiologia , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Feminino , Regulação da Expressão Gênica no Desenvolvimento/genética , Células Germinativas/metabolismo , Ovário/metabolismo , Receptores Citoplasmáticos e Nucleares , Receptores de Esteroides/fisiologia , Transdução de Sinais/fisiologia , Fatores de TranscriçãoRESUMO
Tissue-specific stem cells are tied to the nutritional and physiological environment of adult organisms. Adipocytes have key endocrine and nutrient-sensing roles and have emerged as major players in relaying dietary information to regulate other organs. For example, previous studies in Drosophila melanogaster revealed that amino acid sensing as well as diet-dependent metabolic pathways function in adipocytes to influence the maintenance of female germline stem cells (GSCs). How nutrient-sensing pathways acting within adipocytes influence adult stem cell lineages, however, is just beginning to be elucidated. Here, we report that insulin/insulin-like growth factor signaling in adipocytes promotes GSC maintenance, early germline cyst survival, and vitellogenesis. Further, adipocytes use distinct mechanisms downstream of insulin receptor activation to control these aspects of oogenesis, all of which are independent of FOXO. We find that GSC maintenance is modulated by Akt1 through GSK-3ß, early germline cyst survival is downstream of adipocyte Akt1 but independent of GSK-3ß, and vitellogenesis is regulated through an Akt1-independent pathway in adipocytes. These results indicate that, in addition to employing different types of nutrient sensing, adipocytes can use distinct axes of a single nutrient-sensing pathway to regulate multiple stages of the GSC lineage in the ovary.
Assuntos
Adipócitos/fisiologia , Células-Tronco Germinativas Adultas/fisiologia , Glicogênio Sintase Quinase 3 beta/metabolismo , Adipócitos/metabolismo , Células-Tronco Germinativas Adultas/metabolismo , Animais , Contagem de Células , Proliferação de Células , Drosophila/metabolismo , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/fisiologia , Feminino , Fatores de Transcrição Forkhead/metabolismo , Fatores de Transcrição Forkhead/fisiologia , Células Germinativas/citologia , Glicogênio Sintase Quinase 3 beta/fisiologia , Insulina/metabolismo , Masculino , Oogênese/fisiologia , Ovário/citologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais/fisiologia , Células-Tronco/citologiaRESUMO
Multiple aspects of organismal physiology influence the number and activity of stem cells and their progeny, including nutritional status. Previous studies demonstrated that Drosophila germline stem cells (GSCs), follicle stem cells (FSCs), and their progeny sense and respond to diet via complex mechanisms involving many systemic and local signals. AMP-activated protein kinase, or AMPK, is a highly conserved regulator of energy homeostasis known to be activated under low cellular energy conditions; however, its role in the ovarian response to diet has not been investigated. Here, we describe nutrient-dependent and -independent requirements for AMPK in Drosophila oogenesis. We found that AMPK is cell autonomously required for the slow down in GSC and follicle cell proliferation that occurs on a poor diet. Similarly, AMPK activity is necessary in the germline for the degeneration of vitellogenic stages in response to nutrient deprivation. In contrast, AMPK activity is not required within the germline to modulate its growth. Instead, AMPK acts in follicle cells to negatively regulate their growth and proliferation, thereby indirectly limiting the size of the underlying germline cyst within developing follicles. Paradoxically, AMPK is required for GSC maintenance in well-fed flies (when AMPK activity is presumably at its lowest), suggesting potentially important roles for basal AMPK activity in specific cell types. Finally, we identified a nutrient-independent, developmental role for AMPK in cyst encapsulation by follicle cells. These results uncover specific AMPK requirements in multiple cell types in the ovary and suggest that AMPK can function outside of its canonical nutrient-sensing role in specific developmental contexts.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Dieta , Drosophila melanogaster/metabolismo , Oogênese , Animais , Proliferação de Células , Tamanho Celular , Regulação para Baixo , Endorreduplicação , Comportamento Alimentar , Feminino , Células Germinativas/citologia , Mitose , Folículo Ovariano/citologia , Folículo Ovariano/metabolismo , Células-Tronco/citologia , Células-Tronco/metabolismo , Vitelogeninas/metabolismoRESUMO
How adipocytes contribute to the physiological control of stem cells is a critical question towards understanding the link between obesity and multiple diseases, including cancers. Previous studies have revealed that adult stem cells are influenced by whole-body physiology through multiple diet-dependent factors. For example, nutrient-dependent pathways acting within the Drosophila ovary control the number and proliferation of germline stem cells (GSCs). The potential role of nutrient sensing by adipocytes in modulating stem cells in other organs, however, remains largely unexplored. Here, we report that amino acid sensing by adult adipocytes specifically modulates the maintenance of GSCs through a Target of Rapamycin-independent mechanism. Instead, reduced amino acid levels and the consequent increase in uncoupled tRNAs trigger activation of the GCN2-dependent amino acid response pathway within adipocytes, causing increased rates of GSC loss. These studies reveal a new step in adipocyte-stem cell crosstalk.
Assuntos
Adipócitos/fisiologia , Células-Tronco Adultas/fisiologia , Aminoácidos/metabolismo , Drosophila/fisiologia , Transdução de Sinais/fisiologia , Adipócitos/metabolismo , Animais , Proteínas de Drosophila/metabolismo , Feminino , Microscopia de Fluorescência , Ovário/citologia , Proteínas Quinases/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Serina-Treonina Quinases TOR/metabolismoRESUMO
Adipocytes have key endocrine roles, mediated in large part by secreted protein hormones termed adipokines. The adipokine adiponectin is well known for its role in sensitizing peripheral tissues to insulin, and several lines of evidence suggest that adiponectin might also modulate stem cells/precursors. It remains unclear, however, how adiponectin signaling controls stem cells and whether this role is secondary to its insulin-sensitizing effects or distinct. Drosophila adipocytes also function as an endocrine organ and, although no obvious adiponectin homolog has been identified, Drosophila AdipoR encodes a well-conserved homolog of mammalian adiponectin receptors. Here, we generate a null AdipoR allele and use clonal analysis to demonstrate an intrinsic requirement for AdipoR in germline stem cell (GSC) maintenance in the Drosophila ovary. AdipoR null GSCs are not fully responsive to bone morphogenetic protein ligands from the niche and have a slight reduction in E-cadherin levels at the GSC-niche junction. Conversely, germline-specific overexpression of AdipoR inhibits natural GSC loss, suggesting that reduction in adiponectin signaling might contribute to the normal decline in GSC numbers observed over time in wild-type females. Surprisingly, AdipoR is not required for insulin sensitization of the germline, leading us to speculate that insulin sensitization is a more recently acquired function than stem cell regulation in the evolutionary history of adiponectin signaling. Our findings establish Drosophila female GSCs as a new system for future studies addressing the molecular mechanisms whereby adiponectin receptor signaling modulates stem cell fate.
Assuntos
Adipócitos/fisiologia , Proteínas de Drosophila/metabolismo , Drosophila/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Células Germinativas/citologia , Receptores de Adiponectina/metabolismo , Transdução de Sinais/fisiologia , Células-Tronco/fisiologia , Animais , Animais Geneticamente Modificados , Clonagem Molecular , Primers do DNA/genética , Drosophila/citologia , Proteínas de Drosophila/genética , Feminino , Processamento de Imagem Assistida por Computador , Insulina/metabolismo , Microscopia de Fluorescência , Ovário/citologia , Ovário/metabolismo , Receptores de Adiponectina/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Nuclear hormone receptors have emerged as important regulators of mammalian and Drosophila adult physiology, affecting such seemingly diverse processes as adipogenesis, carbohydrate metabolism, circadian rhythm, stem cell function, and gamete production. Although nuclear hormone receptors Ecdysone Receptor (EcR) and Ultraspiracle (Usp) have multiple known roles in Drosophila development and regulate key processes during oogenesis, the adult function of the majority of nuclear hormone receptors remains largely undescribed. Ecdysone-induced protein 78C (E78), a nuclear hormone receptor closely related to Drosophila E75 and to mammalian Rev-Erb and Peroxisome Proliferator Activated Receptors, was originally identified as an early ecdysone target; however, it has remained unclear whether E78 significantly contributes to adult physiology or reproductive function. To further explore the biological function of E78 in oogenesis, we used available E78 reporters and created a new E78 loss-of-function allele. We found that E78 is expressed throughout the germline during oogenesis, and is important for proper egg production and for the maternal control of early embryogenesis. We showed that E78 is required during development to establish the somatic germline stem cell (GSC) niche, and that E78 function in the germline promotes the survival of developing follicles. Consistent with its initial discovery as an ecdysone-induced target, we also found significant genetic interactions between E78 and components of the ecdysone-signaling pathway. Taken together with the previously described roles of EcR, Usp, and E75, our results suggest that nuclear hormone receptors are critical for the broad transcriptional control of a wide variety of cellular processes during oogenesis.
Assuntos
Proteínas de Drosophila/metabolismo , Drosophila/embriologia , Células-Tronco Embrionárias/fisiologia , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Células Germinativas/fisiologia , Oogênese/fisiologia , Folículo Ovariano/fisiologia , Receptores Citoplasmáticos e Nucleares/metabolismo , Animais , Primers do DNA/genética , Proteínas de Ligação a DNA/metabolismo , Feminino , Galactosídeos , Indóis , Microscopia de Fluorescência , Interferência de RNA , Transdução de Sinais/fisiologia , Fatores de Transcrição/metabolismoRESUMO
Stem cells must proliferate while maintaining 'stemness'; however, much remains to be learned about how factors that control the division of stem cells influence their identity. Multiple stem cell types display cell cycles with short G1 phases, thought to minimize susceptibility to differentiation factors. Drosophila female germline stem cells (GSCs) have short G1 and long G2 phases, and diet-dependent systemic factors often modulate G2. We previously observed that Cyclin E (CycE), a known G1/S regulator, is atypically expressed in GSCs during G2/M; however, it remained unclear whether CycE has cell cycle-independent roles in GSCs or whether it acts exclusively by modulating the cell cycle. In this study, we detected CycE activity during G2/M, reflecting its altered expression pattern, and showed that CycE and its canonical partner, Cyclin-dependent kinase 2 (Cdk2), are required not only for GSC proliferation, but also for GSC maintenance. In genetic mosaics, CycE- and Cdk2-deficient GSCs are rapidly lost from the niche, remain arrested in a G1-like state, and undergo excessive growth and incomplete differentiation. However, we found that CycE controls GSC maintenance independently of its role in the cell cycle; GSCs harboring specific hypomorphic CycE mutations are not efficiently maintained despite normal proliferation rates. Finally, CycE-deficient GSCs have an impaired response to niche bone morphogenetic protein signals that are required for GSC self-renewal, suggesting that CycE modulates niche-GSC communication. Taken together, these results show unequivocally that the roles of CycE/Cdk2 in GSC division cycle regulation and GSC maintenance are separable, and thus potentially involve distinct sets of phosphorylation targets.
Assuntos
Proliferação de Células , Ciclina E/metabolismo , Drosophila/citologia , Nicho de Células-Tronco , Células-Tronco/citologia , Alelos , Animais , Apoptose , Divisão Celular , Ciclina B/genética , Ciclina B/metabolismo , Ciclina E/genética , Quinase 2 Dependente de Ciclina/genética , Quinase 2 Dependente de Ciclina/metabolismo , Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Feminino , Fase G2 , Células Germinativas/citologia , Células Germinativas/metabolismo , Proteínas de Fluorescência Verde/metabolismo , Junções Intercelulares/genética , Junções Intercelulares/metabolismo , Mutação , Fenótipo , Transdução de Sinais , Células-Tronco/metabolismoRESUMO
Stem cells depend on intrinsic and local factors to maintain their identity and activity, but they also sense and respond to changing external conditions. We previously showed that germline stem cells (GSCs) and follicle stem cells (FSCs) in the Drosophila ovary respond to diet via insulin signals. Insulin signals directly modulate the GSC cell cycle at the G2 phase, but additional unknown dietary mediators control both G1 and G2. Target of rapamycin, or TOR, is part of a highly conserved nutrient-sensing pathway affecting growth, proliferation, survival and fertility. Here, we show that optimal TOR activity maintains GSCs but does not play a major role in FSC maintenance, suggesting differential regulation of GSCs versus FSCs. TOR promotes GSC proliferation via G2 but independently of insulin signaling, and TOR is required for the proliferation, growth and survival of differentiating germ cells. We also report that TOR controls the proliferation of FSCs but not of their differentiating progeny. Instead, TOR controls follicle cell number by promoting survival, independently of either the apoptotic or autophagic pathways. These results uncover specific TOR functions in the control of stem cells versus their differentiating progeny, and reveal parallels between Drosophila and mammalian follicle growth.
Assuntos
Proteínas de Drosophila/metabolismo , Proteínas Quinases/metabolismo , Células-Tronco/metabolismo , Animais , Proliferação de Células , Drosophila melanogaster/metabolismo , Feminino , Insulina/metabolismo , Ovário/citologia , Transdução de Sinais , Serina-Treonina Quinases TORRESUMO
Temperature influences male fertility across organisms; however, how suboptimal temperatures affect adult spermatogenesis remains understudied. In a recent study on Drosophila melanogaster oogenesis, we observed a drastic reduction in the fertility of adult males exposed to warm temperature (29 °C). Here, we show that males become infertile at 29 °C because of low sperm abundance and quality. The low sperm abundance at 29 °C does not stem from reduced germline stem cell or spermatid numbers, as those numbers remain comparable between 29 °C and control 25 °C. Notably, males at cold 18 °C and 29 °C had similarly increased frequencies of spermatid elongation and individualization defects which, considering the high sperm abundance and male fertility measured at 18 °C, indicate that spermatogenesis has a high tolerance for elongation and individualization defects. Interestingly, the abundance of sperm at 29 °C decreases abruptly and with no evidence of apoptosis as they transition into the seminal vesicle near the end of spermatogenesis, pointing to sperm elimination through an unknown mechanism. Finally, sperm from males at 29 °C fertilize eggs less efficiently and do not support embryos past the first stage of embryogenesis, indicating that poor sperm quality is an additional cause of male infertility at 29 °C.
Assuntos
Proteínas de Drosophila , Drosophila melanogaster , Animais , Masculino , Temperatura , Sêmen , Espermatozoides , Espermatogênese , FertilidadeRESUMO
Adult stem cells reside in specialized microenvironments, or niches, that are essential for their function in vivo. Stem cells are physically attached to the niche, which provides secreted factors that promote their self-renewal and proliferation. Despite intense research on the role of the niche in regulating stem cell function, much less is known about how the niche itself is controlled. We previously showed that insulin signals directly stimulate germline stem cell (GSC) division and indirectly promote GSC maintenance via the niche in Drosophila. Insulin-like peptides are required for maintenance of cap cells (a major component of the niche) via modulation of Notch signaling, and they also control attachment of GSCs to cap cells and E-cadherin levels at the cap cell-GSC junction. Here, we further dissect the molecular and cellular mechanisms underlying these processes. We show that insulin and Notch ligands directly stimulate cap cells to maintain their numbers and indirectly promote GSC maintenance. We also report that insulin signaling, via phosphoinositide 3-kinase and FOXO, intrinsically controls the competence of cap cells to respond to Notch ligands and thereby be maintained. Contrary to a previous report, we also find that Notch ligands originated in GSCs are not required either for Notch activation in the GSC niche, or for cap cell or GSC maintenance. Instead, the niche itself produces ligands that activate Notch signaling within cap cells, promoting stability of the GSC niche. Finally, insulin signals control cap cell-GSC attachment independently of their role in Notch signaling. These results are potentially relevant to many systems in which Notch signaling modulates stem cells and demonstrate that complex interactions between local and systemic signals are required for proper stem cell niche function.
Assuntos
Drosophila/embriologia , Insulina/farmacologia , Receptores Notch/fisiologia , Transdução de Sinais/fisiologia , Nicho de Células-Tronco/fisiologia , Animais , Proteínas de Drosophila/fisiologia , Feminino , Fatores de Transcrição Forkhead/fisiologia , Ligantes , Fosfatidilinositol 3-Quinases/fisiologia , Receptor de Insulina/fisiologiaRESUMO
Stem cell maintenance depends on local signals provided by specialized microenvironments, or niches, in which they reside. The potential role of systemic factors in stem cell maintenance, however, has remained largely unexplored. Here, we show that insulin signaling integrates the effects of diet and age on germline stem cell (GSC) maintenance through the dual regulation of cap cell number (via Notch signaling) and cap cell-GSC interaction (via E-cadherin) and that the normal process of GSC and niche cell loss that occurs with age can be suppressed by increased levels of insulin-like peptides. These results underscore the importance of systemic factors for the regulation of stem cell niches and, thereby, of stem cell numbers.
Assuntos
Drosophila melanogaster/citologia , Drosophila melanogaster/metabolismo , Insulina/metabolismo , Óvulo/citologia , Nicho de Células-Tronco/citologia , Nicho de Células-Tronco/metabolismo , Células-Tronco/citologia , Animais , Caderinas/metabolismo , Contagem de Células , Drosophila melanogaster/genética , Feminino , Genes de Insetos , Óvulo/metabolismo , Receptor de Insulina/metabolismo , Receptores Notch/metabolismo , Transdução de Sinais , Células-Tronco/metabolismoRESUMO
Reproduction is highly sensitive to changes in physiology and the external environment. Neuropeptides are evolutionarily conserved signaling molecules that regulate multiple physiological processes. However, the potential reproductive roles of many neuropeptide signaling pathways remain underexplored. Here, we describe the results of RNAi-based screens in Drosophila melanogaster to identify neuropeptides/neuropeptide receptors with potential roles in oogenesis. The screen read-outs were either the number of eggs laid per female per day over time or fluorescence microscopy analysis of dissected ovaries. We found that the orphan neuropeptide receptor encoded by moody (homologous to mammalian melatonin receptors) is likely required in somatic cells for normal egg production and proper germline stem cell maintenance. However, the egg laying screens had low signal-to-noise ratio and did not lead to the identification of additional candidates. Thus, although egg count assays might be useful for large-scale screens to identify oogenesis regulators that result in dramatic changes in oogenesis, more labor-intensive microscopy-based screen are better applicable for identifying new physiological regulators of oogenesis with more subtle phenotypes.
Assuntos
Proteínas de Drosophila/deficiência , Proteínas de Drosophila/genética , Drosophila melanogaster/citologia , Drosophila melanogaster/metabolismo , Células-Tronco de Oogônios/citologia , Interferência de RNA , Receptores Acoplados a Proteínas G/deficiência , Receptores Acoplados a Proteínas G/genética , Animais , Drosophila melanogaster/genética , Feminino , Neuropeptídeos/metabolismo , Oogênese , Células-Tronco de Oogônios/metabolismoRESUMO
The physiology of organisms depends on inter-organ communication in response to changes in the environment. Nuclear receptors are broadly expressed transcription factors that respond to circulating molecules to control many biological processes, including immunity, detoxification, and reproduction. Although the tissue-intrinsic roles of nuclear receptors in reproduction have been extensively studied, there is increasing evidence that nuclear receptor signaling in peripheral tissues can also influence oogenesis. We previously showed that the Drosophila nuclear receptor Seven up (Svp) is required in the adult fat body to regulate distinct steps of oogenesis; however, the relevant downstream targets of Svp remain unknown. Here, we took an RNA sequencing approach to identify candidate Svp targets specifically in the adult female fat body that might mediate this response. svp knockdown in the adult female fat body significantly downregulated immune genes involved in the first line of pathogen defense, suggesting a role for Svp in stimulating early immunity. In addition, we found that Svp transcriptionally regulates genes involved in each step of the xenobiotic detoxification response. Based on these findings, we propose a testable model in which Svp functions in the adult female fat body to stimulate early defense against pathogens and facilitate detoxification as part of its mechanisms to promote oogenesis.
Assuntos
Proteínas de Drosophila , Drosophila , Animais , Proteínas de Drosophila/genética , Corpo Adiposo , Feminino , Receptores Citoplasmáticos e Nucleares/genética , Fatores de Transcrição , XenobióticosRESUMO
Precise genetic manipulation of specific cell types or tissues to pinpoint gene function requirement is a critical step in studies aimed at unraveling the intricacies of organismal physiology. Drosophila researchers heavily rely on the UAS/Gal4/Gal80 system for tissue-specific manipulations; however, it is often unclear whether the reported Gal4 expression patterns are indeed specific to the tissue of interest such that experimental results are not confounded by secondary sites of Gal4 expression. Here, we surveyed the expression patterns of commonly used Gal4 drivers in adult Drosophila female tissues under optimal conditions and found that multiple drivers have unreported secondary sites of expression beyond their published cell type/tissue expression pattern. These results underscore the importance of thoroughly characterizing Gal4 tools as part of a rigorous experimental design that avoids potential misinterpretation of results as we strive for understanding how the function of a specific gene/pathway in one tissue contributes to whole-body physiology.
Assuntos
Proteínas de Drosophila , Drosophila , Animais , Drosophila/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Feminino , Técnicas Genéticas , Fatores de Transcrição/genéticaRESUMO
The external environment influences stem cells, but this process is poorly understood. Our previous work showed that germline stem cells (GSCs) respond to diet via neural insulin-like peptides (DILPs) that act directly on the germ line to upregulate stem cell division and cyst growth under a protein-rich diet in Drosophila. Here, we report that DILPs specifically control the G2 phase of the GSC cell cycle via phosphoinositide-3 kinase (PI3K) and dFOXO, and that a separate diet mediator regulates the G1 phase. Furthermore, GSC tumors, which escape the normal stem cell regulatory microenvironment, or niche, still respond to diet via both mechanisms, indicating that niche signals are not required for GSCs to sense or respond to diet. Our results document the effects of diet and insulin-like signals on the cell cycle of stem cells within an intact organism and demonstrate that the response to diet requires multiple signals. Moreover, the retained ability of GSC tumors to respond to diet parallels the long known connections between diet, insulin signaling, and cancer risk in humans.
Assuntos
Dieta , Drosophila/fisiologia , Células Germinativas/fisiologia , Insulina/fisiologia , Neoplasias Embrionárias de Células Germinativas/patologia , Células-Tronco/fisiologia , Animais , Ciclo Celular , Proliferação de Células , Ciclina E/metabolismo , Drosophila/citologia , Drosophila/genética , Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Feminino , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Fase G1 , Fase G2 , Células Germinativas/metabolismo , Células Germinativas/patologia , Imuno-Histoquímica , Insulina/metabolismo , Modelos Biológicos , Oogênese/fisiologia , Ovário/citologia , Ovário/fisiologia , Fosfatidilinositol 3-Quinases/metabolismo , Transdução de Sinais , Células-Tronco/metabolismoRESUMO
Stem cells have a fascinating biology and offer great prospects for therapeutic applications, stimulating intense research on what controls their properties and behavior. Although there have been significant advances in our understanding of how local microenvironments, or niches, control the maintenance and activity of stem cells, it is much less well understood how stem cells sense and respond to variable external, physiological, or tissue environments. This review focuses on the multidirectional interactions among stem cells, niches, tissues, and the systemic environment and on potential ideas for how changes in this network of communication may relate to the aging process.