RESUMO
Regulating the balance between self-renewal (proliferation) and differentiation is key to the long-term functioning of all stem cell pools. In the Caenorhabditis elegans germline, the primary signal controlling this balance is the conserved Notch signaling pathway. Gain-of-function mutations in the GLP-1/Notch receptor cause increased stem cell self-renewal, resulting in a tumour of proliferating germline stem cells. Notch gain-of-function mutations activate the receptor, even in the presence of little or no ligand, and have been associated with many human diseases, including cancers. We demonstrate that reduction in CUP-2 and DER-2 function, which are Derlin family proteins that function in endoplasmic reticulum-associated degradation (ERAD), suppresses the C. elegans germline over-proliferation phenotype associated with glp-1(gain-of-function) mutations. We further demonstrate that their reduction does not suppress other mutations that cause over-proliferation, suggesting that over-proliferation suppression due to loss of Derlin activity is specific to glp-1/Notch (gain-of-function) mutations. Reduction of CUP-2 Derlin activity reduces the expression of a read-out of GLP-1/Notch signaling, suggesting that the suppression of over-proliferation in Derlin loss-of-function mutants is due to a reduction in the activity of the mutated GLP-1/Notch(GF) receptor. Over-proliferation suppression in cup-2 mutants is only seen when the Unfolded Protein Response (UPR) is functioning properly, suggesting that the suppression, and reduction in GLP-1/Notch signaling levels, observed in Derlin mutants may be the result of activation of the UPR. Chemically inducing ER stress also suppress glp-1(gf) over-proliferation but not other mutations that cause over-proliferation. Therefore, ER stress and activation of the UPR may help correct for increased GLP-1/Notch signaling levels, and associated over-proliferation, in the C. elegans germline.
Assuntos
Caenorhabditis elegans/genética , Células Germinativas , Proteínas de Helminto/metabolismo , Neoplasias/metabolismo , Receptores Notch/metabolismo , Animais , Mutação , Neoplasias/patologia , Receptores Notch/genética , Transdução de SinaisRESUMO
MiRNAs post-transcriptionally regulate gene expression by recruiting the miRNA-induced silencing complex (miRISC) to target mRNAs. However, the mechanisms by which miRISC components are maintained at appropriate levels for proper function are largely unknown. Here, we demonstrate that Caenorhabditis elegans TEG-1 regulates the stability of two miRISC effectors, VIG-1 and ALG-1, which in turn affects the abundance of miRNAs in various families. We demonstrate that TEG-1 physically interacts with VIG-1, and complexes with mature let-7 miRNA. Also, loss of teg-1 in vivo phenocopies heterochronic defects observed in let-7 mutants, suggesting the association of TEG-1 with miRISC is necessary for let-7 to function properly during development. Loss of TEG-1 function also affects the abundance and function of other microRNAs, suggesting that TEG-1's role is not specific to let-7. We further demonstrate that the human orthologs of TEG-1, VIG-1 and ALG-1 (CD2BP2, SERBP1/PAI-RBP1 and AGO2) are found in a complex in HeLa cells, and knockdown of CD2BP2 results in reduced miRNA levels; therefore, TEG-1's role in affecting miRNA levels and function is likely conserved. Together, these data demonstrate that TEG-1 CD2BP2 stabilizes miRISC and mature miRNAs, maintaining them at levels necessary to properly regulate target gene expression.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , MicroRNAs/genética , MicroRNAs/metabolismo , Fatores de Processamento de RNA/genética , Fatores de Processamento de RNA/metabolismo , Complexo de Inativação Induzido por RNA/genética , Complexo de Inativação Induzido por RNA/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/antagonistas & inibidores , Animais , Proteínas Argonautas/genética , Proteínas Argonautas/metabolismo , Técnicas de Silenciamento de Genes , Células HeLa , Humanos , Modelos Biológicos , Mutação , Processamento Pós-Transcricional do RNA , Estabilidade de RNA , RNA de Helmintos/genética , RNA de Helmintos/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Ribonucleoproteínas/genética , Ribonucleoproteínas/metabolismoRESUMO
The level of stem cell proliferation must be tightly controlled for proper development and tissue homeostasis. Multiple levels of gene regulation are often employed to regulate stem cell proliferation to ensure that the amount of proliferation is aligned with the needs of the tissue. Here we focus on proteasome-mediated protein degradation as a means of regulating the activities of proteins involved in controlling the stem cell proliferative fate in the C. elegans germ line. We identify five potential E3 ubiquitin ligases, including the RFP-1 RING finger protein, as being involved in regulating proliferative fate. RFP-1 binds to MRG-1, a homologue of the mammalian chromodomain-containing protein MRG15 (MORF4L1), which has been implicated in promoting the proliferation of neural precursor cells. We find that C. elegans with reduced proteasome activity, or that lack RFP-1 expression, have increased levels of MRG-1 and a shift towards increased proliferation in sensitized genetic backgrounds. Likewise, reduction of MRG-1 partially suppresses stem cell overproliferation. MRG-1 levels are controlled independently of the spatially regulated GLP-1/Notch signalling pathway, which is the primary signal controlling the extent of stem cell proliferation in the C. elegans germ line. We propose a model in which MRG-1 levels are controlled, at least in part, by the proteasome, and that the levels of MRG-1 set a threshold upon which other spatially regulated factors act in order to control the balance between the proliferative fate and differentiation in the C. elegans germ line.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/crescimento & desenvolvimento , Diferenciação Celular/fisiologia , Proliferação de Células/fisiologia , Células Germinativas/crescimento & desenvolvimento , Complexo de Endopeptidases do Proteassoma/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Animais , Western Blotting , Caenorhabditis elegans/metabolismo , Proteínas de Transporte/metabolismo , Biologia Computacional , Células Germinativas/metabolismo , Imunoprecipitação , Interferência de RNA , Técnicas do Sistema de Duplo-HíbridoRESUMO
Stem cells are capable of both self-renewal (proliferation) and differentiation. Determining the regulatory mechanisms controlling the balance between stem cell proliferation and differentiation is not only an important biological question, but also holds the key for using stem cells as therapeutic agents. The Caenorhabditis elegans germ line has emerged as a valuable model to study the molecular mechanisms controlling stem cell behavior. In this study, we describe a large-scale RNAi screen that identified kin-10, which encodes the ß subunit of protein kinase CK2, as a novel factor regulating stem cell proliferation in the C. elegans germ line. While a loss of kin-10 in an otherwise wild-type background results in a decrease in the number of proliferative cells, loss of kin-10 in sensitized genetic backgrounds results in a germline tumor. Therefore, kin-10 is not only necessary for robust proliferation, it also inhibits the proliferative fate. We found that kin-10's regulatory role in inhibiting the proliferative fate is carried out through the CK2 holoenzyme, rather than through a holoenzyme-independent function, and that it functions downstream of GLP-1/Notch signaling. We propose that a loss of kin-10 leads to a defect in CK2 phosphorylation of its downstream targets, resulting in abnormal activity of target protein(s) that are involved in the proliferative fate vs. differentiation decision. This eventually causes a shift towards the proliferative fate in the stem cell fate decision.
Assuntos
Caenorhabditis elegans/embriologia , Caseína Quinase II/metabolismo , Diferenciação Celular/genética , Proliferação de Células , Células Germinativas/citologia , Células-Tronco/metabolismo , Sequência de Aminoácidos , Animais , Anticorpos/imunologia , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Caseína Quinase II/genética , Células Germinativas/metabolismo , Fosforilação , Interferência de RNA , RNA Interferente Pequeno , Proteínas de Ligação a RNA/genética , Receptores Notch/genética , Receptores Notch/metabolismo , Alinhamento de Sequência , Transdução de Sinais/genéticaRESUMO
Giardia duodenalis is the most common cause of parasitic diarrhea worldwide and a well-established risk factor for postinfectious irritable bowel syndrome. We hypothesized that Giardia-induced disruptions in host-microbiota interactions may play a role in the pathogenesis of giardiasis and in postgiardiasis disease. Functional changes induced by Giardia in commensal bacteria and the resulting effects on Caenorhabditis elegans were determined. Although Giardia or bacteria alone did not affect worm viability, combining commensal Escherichia coli bacteria with Giardia became lethal to C. elegans. Giardia also induced killing of C. elegans with attenuated Citrobacter rodentium espF and map mutant strains, human microbiota from a healthy donor, and microbiota from inflamed colonic sites of ulcerative colitis patient. In contrast, combinations of Giardia with microbiota from noninflamed sites of the same patient allowed for worm survival. The synergistic lethal effects of Giardia and E. coli required the presence of live bacteria and were associated with the facilitation of bacterial colonization in the C. elegans intestine. Exposure to C. elegans and/or Giardia altered the expression of 172 genes in E. coli. The genes affected by Giardia included hydrogen sulfide biosynthesis (HSB) genes, and deletion of a positive regulator of HSB genes, cysB, was sufficient to kill C. elegans even in the absence of Giardia. Our findings indicate that Giardia induces functional changes in commensal bacteria, possibly making them opportunistic pathogens, and alters host-microbe homeostatic interactions. This report describes the use of a novel in vivo model to assess the toxicity of human microbiota.
Assuntos
Caenorhabditis elegans/microbiologia , Citrobacter rodentium/patogenicidade , Escherichia coli/patogenicidade , Giardia lamblia/patogenicidade , Intestinos/microbiologia , Microbiota , Animais , Estudos de Casos e Controles , Citrobacter rodentium/genética , Citrobacter rodentium/metabolismo , Colite Ulcerativa/microbiologia , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Regulação Bacteriana da Expressão Gênica , Giardia lamblia/metabolismo , Interações Hospedeiro-Patógeno , Humanos , Viabilidade Microbiana , Simbiose , Fatores de Tempo , VirulênciaRESUMO
The C. elegans germ line has emerged as an important model for -understanding how a stem cell population is maintained throughout the life of the animal while still producing the gametes necessary for propagation of the species. The stem cell population in the adult hermaphrodite is relatively large, with stem cells giving rise to daughters that appear intrinsically equivalent; however, some of the daughters retain the proliferative fate while others enter meiotic prophase. While machinery exists for cells to progress through the mitotic cell cycle and machinery exists for cells to progress through meiotic prophase, central to understanding germ line development is identifying the genes and regulatory processes that determine whether the mitotic cell cycle or meiotic prophase machinery will be utilized; in other words, the genes that regulate the switch of germ cells from the proliferative stem cell fate to the meiotic development fate. Whether a germ cell self-renews or enters meiotic prophase is largely determined by its proximity to the distal tip cell (DTC), which is the somatic niche cell that caps the distal end of the gonad. Germ cells close to the DTC have high levels of GLP-1 Notch signaling, which promotes the proliferative fate, while cells further from the DTC have high activity levels of the GLD-1 and GLD-2 redundant RNA regulatory pathways, as well as a third uncharacterized pathway, each of which direct cells to enter meiotic prophase. Other factors and pathways modulate this core genetic pathway, or work in parallel to it, presumably to ensure that a tight balance is maintained between proliferation and meiotic entry.
Assuntos
Caenorhabditis elegans/citologia , Proliferação de Células , Meiose/fisiologia , Células-Tronco/citologia , Animais , Caenorhabditis elegans/crescimento & desenvolvimentoRESUMO
BACKGROUND: For a stem cell population to exist over an extended period, a balance must be maintained between self-renewing (proliferating) and differentiating daughter cells. Within the Caenorhabditis elegans germ line, this balance is controlled by a genetic regulatory pathway, which includes the canonical Notch signaling pathway. RESULTS: Genetic screens identified the gene teg-1 as being involved in regulating the proliferation versus differentiation decision in the C. elegans germ line. Cloning of TEG-1 revealed that it is a homolog of mammalian CD2BP2, which has been implicated in a number of cellular processes, including in U4/U6.U5 tri-snRNP formation in the pre-mRNA splicing reaction. The position of teg-1 in the genetic pathway regulating the proliferation versus differentiation decision, its single mutant phenotype, and its enrichment in nuclei, all suggest TEG-1 also functions as a splicing factor. TEG-1, as well as its human homolog, CD2BP2, directly bind to UAF-1 U2AF65, a component of the U2 auxiliary factor. CONCLUSIONS: TEG-1 functions as a splicing factor and acts to regulate the proliferation versus meiosis decision. The interaction of TEG-1 CD2BP2 with UAF-1 U2AF65, combined with its previously described function in U4/U6.U5 tri-snRNP, suggests that TEG-1 CD2BP2 functions in two distinct locations in the splicing cascade.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/embriologia , Proteínas de Transporte/metabolismo , Proliferação de Células , Células Germinativas/crescimento & desenvolvimento , Ribonucleoproteínas/metabolismo , Processos de Determinação Sexual , Células-Tronco/fisiologia , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Alelos , Processamento Alternativo , Sequência de Aminoácidos , Animais , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Transporte/genética , Diferenciação Celular/genética , Núcleo Celular/metabolismo , Feminino , Células Germinativas/metabolismo , Humanos , Masculino , Meiose/genética , Dados de Sequência Molecular , Mutação , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Fatores de Processamento de RNA , Ribonucleoproteínas/genética , Fator de Processamento U2AF , Células-Tronco/citologiaRESUMO
The constant, ever-increasing antibiotic resistance crisis leads to the announcement of "urgent, novel antibiotics needed" by the World Health Organization. Our previous works showed a promising synergistic antibacterial activity of silver nitrate with potassium tellurite out of thousands of other metal/metalloid-based antibacterial combinations. The silver-tellurite combined treatment not only is more effective than common antibiotics but also prevents bacterial recovery, decreases the risk of future resistance chance, and decreases the effective concentrations. We demonstrate that the silver-tellurite combination is effective against clinical isolates. Further, this study was conducted to address knowledge gaps in the available data on the antibacterial mechanism of both silver and tellurite, as well as to give insight into how the mixture provides synergism as a combination. Here, we defined the differentially expressed gene profile of Pseudomonas aeruginosa under silver, tellurite, and silver-tellurite combination stress using an RNA sequencing approach to examine the global transcriptional changes in the challenged cultures grown in simulated wound fluid. The study was complemented with metabolomics and biochemistry assays. Both metal ions mainly affected four cellular processes, including sulfur homeostasis, reactive oxygen species response, energy pathways, and the bacterial cell membrane (for silver). Using a Caenorhabditis elegans animal model we showed silver-tellurite has reduced toxicity over individual metal/metalloid salts and provides increased antioxidant properties to the host. This work demonstrates that the addition of tellurite would improve the efficacy of silver in biomedical applications. IMPORTANCE Metals and/or metalloids could represent antimicrobial alternatives for industrial and clinical applications (e.g., surface coatings, livestock, and topical infection control) because of their great properties, such as good stability and long half-life. Silver is the most common antimicrobial metal, but resistance prevalence is high, and it can be toxic to the host above a certain concentration. We found that a silver-tellurite composition has antibacterial synergistic effect and that the combination is beneficial to the host. So, the efficacy and application of silver could increase by adding tellurite in the recommended concentration(s). We used different methods to evaluate the mechanism for how this combination can be so incredibly synergistic, leading to efficacy against antibiotic- and silver-resistant isolates. Our two main findings are that (i) both silver and tellurite mostly target the same pathways and (ii) the coapplication of silver with tellurite tends not to target new pathways but targets the same pathways with an amplified change.
Assuntos
Anti-Infecciosos , Metaloides , Animais , Nitrato de Prata/farmacologia , Nitrato de Prata/metabolismo , Pseudomonas aeruginosa/metabolismo , Antibacterianos/química , Anti-Infecciosos/metabolismo , Metaloides/metabolismo , Testes de Sensibilidade MicrobianaRESUMO
The proper production of gametes over an extended portion of the life of an organism is essential for a high level of fitness. The balance between germline stem cell (GSC) proliferation (self-renewal) and differentiation (production of gametes) must be tightly regulated to ensure proper gamete production and overall fitness. Therefore, organisms have evolved robust regulatory systems to control this balance. Here we discuss the redundancy in the regulatory system that controls the proliferation vs. differentiation balance in the C. elegans hermaphrodite germline, and how this redundancy may contribute to robustness. We focus on the various types of redundancy utilized to regulate this balance, as well as the approaches that have enabled these redundant mechanisms to be uncovered.
RESUMO
Plant-based natural compounds (PBCs) are comparatively explored in this study to identify the most effective and safe antibacterial agent/s against six World Health Organization concern pathogens. Based on a contained systematic review, 11 of the most potent PBCs as antibacterial agents are included in this study. The antibacterial and antibiofilm efficacy of the included PBCs are compared with each other as well as common antibiotics (ciprofloxacin and gentamicin). The whole plants of two different strains of Cannabis sativa are extracted to compare the results with sourced ultrapure components. Out of 15 PBCs, tetrahydrocannabinol, cannabidiol, cinnamaldehyde, and carvacrol show promising antibacterial and antibiofilm efficacy. The most common antibacterial mechanisms are explored, and all of our selected PBCs utilize the same pathway for their antibacterial effects. They mostly target the bacterial cell membrane in the initial step rather than the other mechanisms. Reactive oxygen species production and targeting [Fe-S] centres in the respiratory enzymes are not found to be significant, which could be part of the explanation as to why they are not toxic to eukaryotic cells. Toxicity and antioxidant tests show that they are not only nontoxic but also have antioxidant properties in Caenorhabditis elegans as an animal model.
RESUMO
The formation of a fully developed gamete from an undifferentiated germ cell requires progression through numerous developmental stages and cell fate decisions. The precise timing and level of gene expression guides cells through these stages. Translational regulation is highly utilized in the germ line of many species, including Caenorhabditis elegans, to regulate gene expression and ensure the proper formation of gametes. In this review, we discuss some of the developmental stages and cell fate decisions involved in the formation of functional gametes in the C. elegans germ line in which translational control has been implicated. These stages include the mitosis versus meiosis decision, the sperm/oocyte decision, and gamete maturation. We also discuss some of the techniques used to identify mRNA targets; the identification of these targets is necessary to clearly understand the role each RNA-binding protein plays in these decisions. Relatively few mRNA targets have been identified, thus providing a major focus for future research. Finally, we propose some reasons why translational control may be utilized so heavily in the germ line. Given that many species have this substantial reliance on translational regulation for the control of gene expression in the germ line, an understanding of translational regulation in the C. elegans germ line is likely to increase our understanding of gamete formation in general.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/genética , Células Germinativas/metabolismo , Biossíntese de Proteínas , Regiões 3' não Traduzidas/genética , Animais , Proteínas de Caenorhabditis elegans/genética , Transtornos do Desenvolvimento Sexual/genética , Genes de Helmintos , RNA Mensageiro/genética , Proteínas de Ligação a RNA/genéticaRESUMO
BACKGROUND: Germ cells must progress through elaborate developmental stages from an undifferentiated germ cell to a fully differentiated gamete. Some of these stages include exiting mitosis and entering meiosis, progressing through the various stages of meiotic prophase, adopting either a male (sperm) or female (oocyte) fate, and completing meiosis. Additionally, many of the factors needed to drive embryogenesis are synthesized in the germ line. To increase our understanding of the genes that might be necessary for the formation and function of the germ line, we have constructed a SAGE library from hand dissected C. elegans hermaphrodite gonads. RESULTS: We found that 4699 genes, roughly 21% of all known C. elegans genes, are expressed in the adult hermaphrodite germ line. Ribosomal genes are highly expressed in the germ line; roughly four fold above their expression levels in the soma. We further found that 1063 of the germline-expressed genes have enriched expression in the germ line as compared to the soma. A comparison of these 1063 germline-enriched genes with a similar list of genes prepared using microarrays revealed an overlap of 460 genes, mutually reinforcing the two lists. Additionally, we identified 603 germline-enriched genes, supported by in situ expression data, which were not previously identified. We also found >4 fold enrichment for RNA binding proteins in the germ line as compared to the soma. CONCLUSION: Using multiple technological platforms provides a more complete picture of global gene expression patterns. Genes involved in RNA metabolism are expressed at a significantly higher level in the germ line than the soma, suggesting a stronger reliance on RNA metabolism for control of the expression of genes in the germ line. Additionally, the number and expression level of germ line expressed genes on the X chromosome is lower than expected based on a random distribution.
Assuntos
Caenorhabditis elegans/genética , Perfilação da Expressão Gênica/métodos , Genes de Helmintos , Células Germinativas/metabolismo , Animais , Transtornos do Desenvolvimento Sexual/genética , Biblioteca Gênica , Análise de Sequência com Séries de Oligonucleotídeos , RNA de Helmintos/metabolismo , Proteínas de Ligação a RNA/genéticaRESUMO
Reproductive fitness in many animals relies upon a tight balance between the number of cells that proliferate in the germ line and the number of cells that enter meiosis and differentiate as gametes. In the Caenorhabditis elegans germ line, the GLP-1/Notch signaling pathway controls this balance between proliferation and meiotic entry. Here we describe the identification of the proteasome as an additional regulator of this balance. We show that a decrease in proteasome activity, through either genetic mutation or RNAi to core components of the proteasome, shifts this balance toward excess germ-line proliferation. We further demonstrate that there are likely two or more proteasome targets that contribute to excess germ-line proliferation when proteasome activity is reduced. One of these targets is likely a component or regulator of the Notch-signaling pathway, while the other functions on one of the two major redundant genetic pathways downstream of GLP-1/Notch signaling. We propose a model in which the proteasome degrades proteins that are necessary for proliferation as cells switch from proliferation to meiotic entry.
Assuntos
Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proliferação de Células , Gônadas/crescimento & desenvolvimento , Meiose , Complexo de Endopeptidases do Proteassoma/metabolismo , Sequência de Aminoácidos , Animais , Caenorhabditis elegans/enzimologia , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Células Germinativas , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Modelos Biológicos , Dados de Sequência Molecular , Polinucleotídeo Adenililtransferase/genética , Polinucleotídeo Adenililtransferase/metabolismo , Receptores Notch/genética , Receptores Notch/metabolismo , Transdução de SinaisRESUMO
A major event in germline development is the transition from stem/progenitor cells to entry into meiosis and gametogenesis. This transition requires downregulation of mitotic cell cycle activity and upregulation of processes associated with meiosis. We identify the Caenorhabditis elegans SCFPROM-1 E3 ubiquitin-ligase complex as functioning to downregulate mitotic cell cycle protein levels including cyclin E, WAPL-1, and KNL-2 at meiotic entry and, independently, promoting homologous chromosome pairing as a positive regulator of the CHK-2 kinase. SCFPROM-1 is thus a novel regulator of meiotic entry, coordinating downregulation of mitotic cell cycle proteins and promoting homolog pairing. We further show that SCFPROM-1 functions redundantly, in parallel to the previously described GLD-1 and GLD-2 meiotic entry pathways, downstream of and inhibited by GLP-1 Notch signaling, which specifies the stem cell fate. Accordingly, C. elegans employs three post-transcriptional pathways, SCFPROM-1-mediated protein degradation, GLD-1-mediated translational repression, and GLD-2-mediated translational activation, to control and coordinate the initiation of meiotic development.
Assuntos
Caenorhabditis elegans/fisiologia , Redes Reguladoras de Genes , Meiose , Transdução de Sinais , Animais , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/genética , Proteínas de Ciclo Celular/genética , Quinase do Ponto de Checagem 2/genética , Proteínas de Drosophila/genética , Proteínas F-Box/genética , Gametogênese , Regulação da Expressão Gênica , Polinucleotídeo Adenililtransferase/genética , Biossíntese de Proteínas , Proteólise , Receptores Notch/genéticaRESUMO
In many animals, reproductive fitness is dependent upon the production of large numbers of gametes over an extended period of time. This level of gamete production is possible due to the continued presence of germ line stem cells. These cells can produce two types of daughter cells, self-renewing daughter cells that will maintain the stem cell population and differentiating daughter cells that will become gametes. A balance must be maintained between the proliferating self-renewing cells and those that differentiate for long-term gamete production to be maintained. Too little proliferation can result in depletion of the stem cell population, while too little differentiation can lead to a lack of gamete formation and possible tumor formation. In this chapter, we discuss our current understanding of how the balance between proliferation and differentiation is achieved in three well-studied germ line model systems: the Drosophila female, the mouse male, and the C. elegans hermaphrodite. While these three systems have significant differences in how this balance is regulated, including differences in stem cell population size, signaling pathways utilized, and the use of symmetric and/or asymmetric cell divisions, there are also similarities found between them. These similarities include the reliance on a predominant signaling pathway to promote proliferation, negative feedback loops to rapidly shutoff proliferation-promoting cues, close association of the germ line stem cells with a somatic niche, cytoplasmic connections between cells, projections emanating from the niche cell, and multiple mechanisms to limit the spatial influence of the niche. A comparison between different systems may help to identify elements that are essential for a proper balance between proliferation and differentiation to be achieved and elements that may be achieved through various mechanisms.
Assuntos
Diferenciação Celular/fisiologia , Proliferação de Células/fisiologia , Células Germinativas/citologia , Animais , Caenorhabditis elegans , Drosophila , Feminino , Masculino , CamundongosRESUMO
SAVSBPM18 is an engineered streptavidin for affinity purification of both biotinylated biomolecules and recombinant proteins tagged with streptavidin binding peptide (SBP) tags. To develop a user-friendly approach for the preparation of the SAVSBPM18-based affinity matrices, a designer fusion protein containing SAVSBPM18 and a galactose binding domain was engineered. The galactose binding domain derived from the earthworm lectin EW29 was genetically modified to eliminate a proteolytic cleavage site located at the beginning of the domain. This domain was fused to the C-terminal end of SAVSBPM18. It allows the SAVSBPM18 fusions to bind reversibly to agarose and can serve as an affinity handle for purification of the fusion. Fluorescently labeled SAVSBPM18 fusions were found to be stably immobilized on Sepharose 6B-CL. The enhanced immobilization capability of the fusion to the agarose beads results from the avidity effect mediated by the tetrameric nature of SAVSBPM18. This approach allows the consolidation of purification and immobilization of SAVSBPM18 fusions to Sepharose 6B-CL in one step for affinity matrix preparation. The resulting affinity matrix has been successfully applied to purify both SBP tagged ß-lactamase and biotinylated proteins. No significant reduction in binding capacity of the column was observed for at least six months.
Assuntos
Cromatografia de Afinidade/métodos , Sefarose/análogos & derivados , Estreptavidina/metabolismo , Animais , Biotinilação , Escherichia coli/metabolismo , Galectinas/química , Galectinas/genética , Galectinas/metabolismo , Proteínas Imobilizadas/química , Proteínas Imobilizadas/metabolismo , Oligoquetos/metabolismo , Proteínas Recombinantes de Fusão/biossíntese , Proteínas Recombinantes de Fusão/química , Sefarose/química , Sefarose/metabolismo , Soroalbumina Bovina/química , Soroalbumina Bovina/isolamento & purificação , Estreptavidina/química , Estreptavidina/genética , beta-Lactamases/isolamento & purificaçãoRESUMO
In the Caenorhabditis elegans germline, proliferation is induced by Notch-type signaling. Entry of germ cells into meiosis is triggered by activity of the GLD-1 and GLD-2 pathways, which function redundantly to promote meiosis and/or inhibit proliferation. Activation of the germline Notch-type receptor, GLP-1, ultimately inhibits the activities of the GLD-1 and GLD-2 pathways. We previously identified several ego (enhancer of glp-1) genes that promote germline proliferation and interact genetically with the GLP-1 signaling pathway. Here, we show that atx-2 is an ego gene. Our data suggest that ATX-2 is not a positive regulator of the GLP-1 signaling pathway and GLP-1 signaling is not the sole positive regulator of ATX-2 activity. Moreover, our data indicate that GLP-1 must have an additional function, which may be to repress activity of a third meiotic entry pathway that would work in parallel with the GLD-1 and GLD-2 pathways. In addition to its role in proliferation, ATX-2 acts downstream of FOG-2 to promote the female germline fate.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/fisiologia , Proliferação de Células , Meiose/fisiologia , Glicoproteínas de Membrana/metabolismo , Oócitos/fisiologia , Proteínas/metabolismo , Sequência de Aminoácidos , Animais , Repetição de Anquirina , Ataxinas , Feminino , Células Germinativas , Dados de Sequência Molecular , Proteínas do Tecido Nervoso , Polinucleotídeo Adenililtransferase/metabolismo , Proteínas/antagonistas & inibidores , Proteínas/genética , Interferência de RNA , Receptores Notch , Homologia de Sequência de Aminoácidos , Transdução de SinaisRESUMO
To investigate the causes and functional significance of rapid sex-determining protein evolution we compared three Caenorhabditis elegans genes encoding members of the protein phosphatase 2C (PP2C) family with their orthologs from another Caenorhabditis species (strain CB5161). One of the genes encodes FEM-2, a sex-determining protein, while the others have no known sex-determining role. FEM-2's PP2C domain was found to be more diverged than the other PP2C domains, supporting the notion that sex-determining proteins are subjected to selective pressures that allow for or cause rapid divergence. Comparison of the positions of amino acid substitutions in FEM-2 with a solved three-dimensional structure suggests that the catalytic face of the protein is highly conserved among C. elegans, CB5161, and another closely related species C. briggsae. However, the non-conserved regions of FEM-2 cannot be said to lack functional importance, since fem-2 transgenes from the other species were unable to rescue the germ-line defect caused by a C. elegans fem-2 mutation. To test whether fem-2 functions as a sex-determining gene in the other Caenorhabditis species we used RNA-mediated interference (RNAi). fem-2 (RNAi) in C. elegans and C. briggsae caused germ-line feminization, but had no noticeable effect in CB5161. Thus the function of fem-2 in CB5161 remains uncertain.
Assuntos
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis/enzimologia , Caenorhabditis/genética , Evolução Molecular , Variação Genética , Fosfoproteínas Fosfatases/genética , Processos de Determinação Sexual , Sequência de Aminoácidos , Animais , Animais Geneticamente Modificados , Proteínas de Caenorhabditis elegans/metabolismo , Domínio Catalítico , Sequência Conservada , Transtornos do Desenvolvimento Sexual/genética , Regulação Enzimológica da Expressão Gênica , Genoma/genética , Células Germinativas , Humanos , Modelos Moleculares , Dados de Sequência Molecular , Mutação/genética , Fosfoproteínas Fosfatases/química , Fosfoproteínas Fosfatases/metabolismo , Proteína Fosfatase 2C , Interferência de RNA , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Mapeamento por Restrição , Alinhamento de Sequência , Peixe-Zebra/genéticaRESUMO
In many animals, oocytes enter meiosis early in their development but arrest in meiotic prophase I. Oocyte growth, which occurs during this arrest period, enables the acquisition of meiotic competence and the capacity to produce healthy progeny. Meiotic resumption, or meiotic maturation, involves the transition to metaphase I (M phase) and is regulated by intercellular signaling and cyclin-dependent kinase activation. Premature meiotic maturation would be predicted to diminish fertility as the timing of this event, which normally occurs after oocyte growth is complete, is crucial. In the accompanying article in this issue, we identify the highly conserved TRIM-NHL protein LIN-41 as a translational repressor that copurifies with OMA-1 and OMA-2, RNA-binding proteins redundantly required for normal oocyte growth and meiotic maturation. In this article, we show that LIN-41 enables the production of high-quality oocytes and plays an essential role in controlling and coordinating oocyte growth and meiotic maturation. lin-41 null mutants display a striking defect that is specific to oogenesis: pachytene-stage cells cellularize prematurely and fail to progress to diplotene. Instead, these cells activate CDK-1, enter M phase, assemble spindles, and attempt to segregate chromosomes. Translational derepression of the CDK-1 activator CDC-25.3 appears to contribute to premature M-phase entry in lin-41 mutant oocytes. Genetic and phenotypic analyses indicate that LIN-41 and OMA-1/2 exhibit an antagonistic relationship, and we suggest that translational regulation by these proteins could be important for controlling and coordinating oocyte growth and meiotic maturation.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Metáfase , Oócitos/metabolismo , Prófase , Proteínas de Ligação a RNA/metabolismo , Fatores de Transcrição/metabolismo , Animais , Proteína Quinase CDC2/metabolismo , Proteínas de Caenorhabditis elegans/química , Proteínas de Caenorhabditis elegans/genética , Proteínas de Transporte/metabolismo , Ciclo Celular/genética , Feminino , Fertilidade/genética , Expressão Gênica , Regulação da Expressão Gênica , Ordem dos Genes , Loci Gênicos , Genótipo , Masculino , Meiose/genética , Metáfase/genética , Mutação , Não Disjunção Genética , Oogênese/genética , Prófase/genética , Domínios e Motivos de Interação entre Proteínas , Splicing de RNA , Espermatogênese/genética , Fatores de Transcrição/química , Fatores de Transcrição/genéticaRESUMO
Stem cell populations are maintained by keeping a balance between self-renewal (proliferation) and differentiation of dividing stem cells. Within the Caenorhabditis elegans germline, the key regulator maintaining this balance is the canonical Notch signaling pathway, with GLP-1/Notch activity promoting the proliferative fate. We identified the Pumilio homolog, PUF-8, as an inhibitor of the proliferative fate of stem cells in the C. elegans germline. puf-8(0) strongly enhances overproliferation of glp-1(gf) mutants and partially suppresses underproliferation of a weak glp-1(lf) mutant. The germline tumor that is formed in a puf-8(0); glp-1(gf) double mutant is due to a failure of germ cells to enter meiotic prophase. puf-8 likely inhibits the proliferative fate through negatively regulating GLP-1/Notch signaling or by functioning parallel to it.