RESUMEN
Selfish DNA modules like transposable elements (TEs) are particularly active in the germline, the lineage that passes genetic information across generations. New TE insertions can disrupt genes and impair the functionality and viability of germ cells. However, we found that in P-M hybrid dysgenesis in Drosophila, a sterility syndrome triggered by the P-element DNA transposon, germ cells harbor unexpectedly few new TE insertions despite accumulating DNA double-strand breaks (DSBs) and inducing cell cycle arrest. Using an engineered CRISPR-Cas9 system, we show that generating DSBs at silenced P-elements or other noncoding sequences is sufficient to induce germ cell loss independently of gene disruption. Indeed, we demonstrate that both developing and adult mitotic germ cells are sensitive to DSBs in a dosage-dependent manner. Following the mitotic-to-meiotic transition, however, germ cells become more tolerant to DSBs, completing oogenesis regardless of the accumulated genome damage. Our findings establish DNA damage tolerance thresholds as crucial safeguards of genome integrity during germline development.
Asunto(s)
Roturas del ADN de Doble Cadena , Elementos Transponibles de ADN , Células Germinativas , Animales , Elementos Transponibles de ADN/genética , Sistemas CRISPR-Cas/genética , Daño del ADN/genética , Drosophila melanogaster/genética , Femenino , Oogénesis/genéticaRESUMEN
Throughout metazoa, germ cells assemble RNA-protein organelles (germ granules). In Drosophila ovaries, perinuclear nuage forms in the nurse cells, while compositionally similar polar granules form in the oocyte. A similar system appears to exist in the distantly related (â¼350 million years) wasp Nasonia, with some surprising divergences. Nuage is similarly formed in Nasonia, except that anterior nurse cells accumulate significantly more nuage, in association with high levels of DNA double-strand breaks, suggesting that increased transposon activity in anterior is silenced by high nuage levels. In the oocyte, the germ plasm forms a single granule that is 40 times larger than a homologous Drosophila polar granule. While conserved germ granule proteins are recruited to the oosome, they show unusual localization: Tudor protein forms a shell encapsulating the embryonic oosome, while small Oskar/Vasa/Aubergine granules coalesce interiorly. Wasp Vasa itself is unusual since it has an alternative splice form that includes a novel nucleoporin-like phenylalanine-glycine repeat domain. Our work is consistent with the high degree of evolutionary plasticity of membraneless organelles and describes new experimental model and resources to study biomolecular condensates.
RESUMEN
Primordial germ cells (PGCs) are the precursors of sperms and oocytes. Proper development of PGCs is crucial for the survival of the species. In many organisms, factors responsible for PGC development are synthesized during early oogenesis and assembled into the germ plasm. During early embryonic development, germ plasm is inherited by a few cells, leading to the formation of PGCs. While germline development has been extensively studied, how components of the germ plasm regulate PGC development is not fully understood. Here, we report that Dzip1 is dynamically expressed in vertebrate germline and is a novel component of the germ plasm in Xenopus and zebrafish. Knockdown of Dzip1 impairs PGC development in Xenopus embryos. At the molecular level, Dzip1 physically interacts with Dazl, an evolutionarily conserved RNA-binding protein that plays a multifaced role during germline development. We further showed that the sequence between amino acid residues 282 and 550 of Dzip1 is responsible for binding to Dazl. Disruption of the binding between Dzip1 and Dazl leads to defective PGC development. Taken together, our results presented here demonstrate that Dzip1 is dynamically expressed in the vertebrate germline and plays a novel function during Xenopus PGC development.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales , Regulación del Desarrollo de la Expresión Génica , Células Germinativas , Proteínas de Unión al ARN , Proteínas de Xenopus , Xenopus laevis , Animales , Femenino , Células Germinativas/metabolismo , Células Germinativas/citología , Oogénesis/genética , Proteínas de Unión al ARN/metabolismo , Proteínas de Unión al ARN/genética , Xenopus laevis/embriología , Xenopus laevis/metabolismo , Xenopus laevis/genética , Proteínas de Xenopus/metabolismo , Proteínas de Xenopus/genética , Pez Cebra/embriología , Pez Cebra/genética , Pez Cebra/metabolismo , Proteínas de Pez Cebra/metabolismo , Proteínas de Pez Cebra/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismoRESUMEN
The maintenance of genome integrity in the germline is crucial for mammalian development. Long interspersed element type 1 (LINE-1, L1) is a mobile genetic element that makes up about 17% of the human genome and poses a threat to genome integrity. N6-methyl-adenosine (m6A) plays an essential role in regulating various biological processes. However, the function of m6A modification in L1 retrotransposons and human germline development remains largely unknown. Here we knocked out the m6A methyltransferase METTL3 or the m6A reader YTHDF2 in human embryonic stem cells (hESCs) and discovered that METTL3 and YTHDF2 are crucial for inducing human spermatogonial stem cells (hSSCs) from hESCs in vitro. The removal of METTL3 or YTHDF2 resulted in increased L1 retrotransposition and reduced the efficiency of SSC differentiation in vitro. Further analysis showed that YTHDF2 recognizes the METTL3-catalyzed m6A modification of L1 retrotransposons and degrades L1 mRNA through autophagy, thereby blocking L1 retrotransposition. Moreover, the study confirmed that m6A modification in human fetal germ cells promotes the degradation of L1 retrotransposon RNA, preventing the insertion of new L1 retrotransposons into the genome. Interestingly, L1 retrotransposon RNA was highly expressed while METTL3 was significantly downregulated in the seminal plasma of azoospermic patients with meiotic arrest compared to males with normal fertility. Additionally, we identified some potentially pathogenic variants in m6A-related genes in azoospermic men with meiotic arrest. In summary, our study suggests that m6A modification serves as a guardian of genome stability during human germline development and provides novel insights into the function and regulatory mechanisms of m6A modification in restricting L1 retrotransposition.
Asunto(s)
Azoospermia , Retroelementos , Masculino , Animales , Humanos , Retroelementos/genética , ARN , Azoospermia/genética , Diferenciación Celular/genética , Metiltransferasas/genética , Metiltransferasas/metabolismo , ARN Mensajero/genética , Mamíferos/metabolismoRESUMEN
The C. elegans germline is organized as a syncytium in which each germ cell possesses an intercellular bridge that is maintained by a stable actomyosin ring and connected to a common pool of cytoplasm, termed the rachis. How germ cells undergo cytokinesis while maintaining this syncytial architecture is not completely understood. Here, we use live imaging to characterize primordial germ cell (PGC) division in C. elegans first-stage larvae. We show that each PGC possesses a stable intercellular bridge that connects it to a common pool of cytoplasm, which we term the proto-rachis. We further show that the first PGC cytokinesis is incomplete and that the stabilized cytokinetic ring progressively moves towards the proto-rachis and eventually integrates with it. Our results support a model in which the initial expansion of the C. elegans syncytial germline occurs by incomplete cytokinesis, where one daughter germ cell inherits the actomyosin ring that was newly formed by stabilization of the cytokinetic ring, while the other inherits the pre-existing stable actomyosin ring. We propose that such a mechanism of iterative cytokinesis incompletion underpins C. elegans germline expansion and maintenance.
Asunto(s)
Caenorhabditis elegans/citología , Citocinesis/fisiología , Células Germinativas/citología , Citoesqueleto de Actina/fisiología , Actomiosina/fisiología , Animales , Citoplasma/fisiología , Células Gigantes/fisiologíaRESUMEN
Specification of the germline and its segregation from the soma mark one of the most crucial events in the lifetime of an organism. In different organisms, this specification can occur through either inheritance or inductive mechanisms. In species such as Xenopus and zebrafish, the specification of primordial germ cells relies on the inheritance of maternal germline determinants that are synthesized and sequestered in the germ plasm during oogenesis. In this review, we discuss the formation of the germ plasm, how germline determinants are recruited into the germ plasm during oogenesis, and the dynamics of the germ plasm during oogenesis and early embryonic development.
Asunto(s)
Desarrollo Embrionario , Oogénesis , Pez Cebra , Animales , Oogénesis/fisiología , Pez Cebra/embriología , Desarrollo Embrionario/fisiología , Células Germinativas/metabolismo , Femenino , Xenopus/embriologíaRESUMEN
BACKGROUND: Disrupted germline differentiation or compromised testis development can lead to subfertility or infertility and are strongly associated with testis cancer in humans. In mice, SRY and SOX9 induce expression of Fgf9, which promotes Sertoli cell differentiation and testis development. FGF9 is also thought to promote male germline differentiation but the mechanism is unknown. FGFs typically signal through mitogen-activated protein kinases (MAPKs) to phosphorylate ERK1/2 (pERK1/2). We explored whether FGF9 regulates male germline development through MAPK by inhibiting either FGF or MEK1/2 signalling in the foetal testis immediately after gonadal sex determination and testis cord formation, but prior to male germline commitment. RESULTS: pERK1/2 was detected in Sertoli cells and inhibition of MEK1/2 reduced Sertoli cell proliferation and organisation and resulted in some germ cells localised outside of the testis cords. While pERK1/2 was not detected in germ cells, inhibition of MEK1/2 after somatic sex determination profoundly disrupted germ cell mitotic arrest, dysregulated a broad range of male germline development genes and prevented the upregulation of key male germline markers, DPPA4 and DNMT3L. In contrast, while FGF inhibition reduced Sertoli cell proliferation, expression of male germline markers was unaffected and germ cells entered mitotic arrest normally. While male germline differentiation was not disrupted by FGF inhibition, a range of stem cell and cancer-associated genes were commonly altered after 24 h of FGF or MEK1/2 inhibition, including genes involved in the maintenance of germline stem cells, Nodal signalling, proliferation, and germline cancer. CONCLUSIONS: Together, these data demonstrate a novel role for MEK1/2 signalling during testis development that is essential for male germline differentiation, but indicate a more limited role for FGF signalling. Our data indicate that additional ligands are likely to act through MEK1/2 to promote male germline differentiation and highlight a need for further mechanistic understanding of male germline development.
Asunto(s)
Neoplasias , Testículo , Masculino , Ratones , Humanos , Animales , Testículo/metabolismo , Factor 2 de Crecimiento de Fibroblastos , Células Germinativas , Diferenciación Celular , Neoplasias/metabolismoRESUMEN
In most species, early germline development occurs in the absence of transcription with germline determinants subject to complex translational and post-translational regulations. Here, we report for the first time that early germline development is influenced by dynamic regulation of the proteasome system, previously thought to be ubiquitously expressed and to serve 'housekeeping' roles in controlling protein homeostasis. We show that proteasomes are present in a gradient with the highest levels in the animal hemisphere and extending into the vegetal hemisphere of Xenopus oocytes. This distribution changes dramatically during the oocyte-to-embryo transition, with proteasomes becoming enriched in and restricted to the animal hemisphere and therefore separated from vegetally localized germline determinants. We identify Dead-end1 (Dnd1), a master regulator of vertebrate germline development, as a novel substrate of the ubiquitin-independent proteasomes. In the oocyte, ubiquitin-independent proteasomal degradation acts together with translational repression to prevent premature accumulation of Dnd1 protein. In the embryo, artificially increasing ubiquitin-independent proteasomal degradation in the vegetal pole interferes with germline development. Our work thus reveals novel inhibitory functions and spatial regulation of the ubiquitin-independent proteasome during vertebrate germline development.
Asunto(s)
Células Germinativas/metabolismo , Ubiquitina/metabolismo , Animales , Citoplasma/metabolismo , Células Germinativas/citología , Oocitos/metabolismo , Complejo de la Endopetidasa Proteasomal/metabolismo , Proteínas de Unión al ARN/metabolismo , Ubiquitina/genética , Proteínas de Xenopus/metabolismo , Xenopus laevisRESUMEN
PURPOSE: The requirement of zinc for the development and maturation of germ lines and reproductive systems is deeply conserved across evolution. The nematode Caenorhabditis elegans offers a tractable platform to study the complex system of distributing zinc to the germ line. We investigated several zinc importers to investigate how zinc transporters play a role in the reproductive system in nematodes, as well as establish a platform to study zinc transporter biology in germline and reproductive development. METHODS: Previous high throughput transcriptional datasets as well as phylogenetic analysis identified several putative zinc transporters that have a function in reproduction in worms. Phenotypic analysis of CRISPR-generated knockouts and tags included characterization of offspring output, gonad development, and protein localization. Light and immunofluorescence microscopy allowed for visualization of physiological and molecular effects of zinc transporter mutations. RESULTS: Disruption of two zinc transporters, ZIPT-2.4 and ZIPT-15, was shown to lead to defects in reproductive output. A mutation in zipt-2.4 has subtle effects on reproduction, while a mutation in zipt-15 has a clear impact on gonad and germline development that translates into a more pronounced defect in fecundity. Both transporters have germline expression, as well as additional expression in other cell types. CONCLUSIONS: Two ZIP-family zinc transporter orthologs of human ZIP6/10 and ZIP1/2/3 proteins are important for full reproductive fecundity and participate in development of the gonad. Notably, these zinc transporters are present in gut and reproductive tissues in addition to the germ line, consistent with a complex zinc trafficking network important for reproductive success.
Asunto(s)
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Proteínas Portadoras , Proteínas de Transporte de Catión , Animales , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Proteínas de Transporte de Catión/genética , Proteínas de Transporte de Catión/metabolismo , Fertilidad , Células Germinativas/metabolismo , Humanos , Filogenia , Zinc/metabolismoRESUMEN
Poly(U) polymerases (PUPs) catalyze 3' uridylation of mRNAs and small RNAs, a modification often correlating with decreased RNA stability. We have investigated the importance of three proteins with in vitro PUP activity, PUP-1/CDE-1, PUP-2 and PUP-3, in C. elegans germline development. Genetic analysis indicates that PUP-1/CDE-1 and PUP-2 are developmentally redundant under conditions of temperature stress during which they ensure germline viability and development. Multiple lines of evidence indicate that pup-1/-2 double mutant germ cells fail to maintain their identity as distinct from soma. Consistent with phenotypic data, PUP-1 and PUP-2 are expressed in embryonic germ cell precursors and throughout germline development. The developmental importance of PUP activity is presumably in regulating gene expression as both a direct and indirect consequence of modifying target RNAs. PUP-3 is significantly overexpressed in the pup-1/-2 germline, and loss of pup-3 function partially suppresses pup-1/-2 germline defects. We conclude that one major function of PUP-1/-2 is to limit PUP-3 expression. Overall, the balance of PUP-1, PUP-2 and PUP-3 activities appears to ensure proper germline development.
Asunto(s)
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/embriología , Caenorhabditis elegans/enzimología , ARN Polimerasas Dirigidas por ADN/metabolismo , Desarrollo Embrionario , Células Germinativas/metabolismo , Animales , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/genética , ARN Polimerasas Dirigidas por ADN/genética , Embrión no Mamífero/metabolismo , Femenino , Fertilización , Regulación del Desarrollo de la Expresión Génica , Genes Reporteros , Proteínas Fluorescentes Verdes/metabolismo , Masculino , Modelos Biológicos , Mutación/genética , Neuronas/metabolismo , Espermatozoides/metabolismo , Análisis de Supervivencia , Regulación hacia Arriba/genéticaRESUMEN
In the developing embryo, primordial germ cells (PGCs) represent the exclusive progenitors of the gametes, and their loss results in adult infertility. During early development, PGCs are exposed to numerous signals that specify somatic cell fates. To prevent somatic differentiation, PGCs must transiently silence their genome, an early developmental process that requires Nanos activity. However, it is unclear how Nanos translation is regulated in developing embryos. We report here that translation of nanos1 after fertilization requires Dead-end 1 (Dnd1), a vertebrate-specific germline RNA-binding protein. We provide evidence that Dnd1 protein, expression of which is low in oocytes, but increases dramatically after fertilization, directly interacts with, and relieves the inhibitory function of eukaryotic initiation factor 3f, a repressive component in the 43S preinitiation complex. This work uncovers a novel translational regulatory mechanism that is fundamentally important for germline development.
Asunto(s)
Factor 3 de Iniciación Eucariótica/metabolismo , Proteínas de Unión al ARN/metabolismo , Proteínas Represoras/metabolismo , Proteínas de Xenopus/metabolismo , Xenopus laevis , Animales , Diferenciación Celular , Femenino , Fertilización , Regulación del Desarrollo de la Expresión Génica , Células HEK293 , Humanos , Ratones , Oocitos/metabolismo , Iniciación de la Cadena Peptídica Traduccional , Plásmidos/metabolismo , Unión Proteica , Biosíntesis de Proteínas , Transducción de SeñalRESUMEN
Transgenerational transmission of genome-regulatory epigenetic information can determine phenotypes in the progeny of sexual reproduction. Sequence specificity of transgenerational regulation derives from small RNAs assembled into Piwi-protein complexes. Known targets of transgenerational regulation are primarily transposons and transposon-derived sequences. Here, we extend the scope of Piwi-mediated transgenerational regulation to include unique noncoding RNA loci. Ciliates such as Tetrahymena have a phenotypically silent germline micronucleus and an expressed somatic macronucleus, which is differentiated anew from a germline genome copy in sexual reproduction. We show that the nuclear-localized Tetrahymena Piwi protein Twi8p shuttles from parental to zygotic macronuclei. Genetic elimination of Twi8p has no phenotype for cells in asexual growth. On the other hand, cells lacking Twi8p arrest in sexual reproduction with zygotic nuclei that retain the germline genome structure, without the DNA elimination and fragmentation required to generate a functional macronucleus. Twi8p-bound small RNAs originate from long-noncoding RNAs with a terminal hairpin, which become detectable in the absence of Twi8p. Curiously, the loci that generate Twi8p-bound small RNAs are essential for asexual cell growth, even though Twi8 RNPs are essential only in sexual reproduction. Our findings suggest the model that Twi8 RNPs act on silent germline chromosomes to permit their conversion to expressed macronuclear chromosomes. Overall this work reveals that a Piwi protein carrying small RNAs from long-noncoding RNA loci has transgenerational function in establishing zygotic nucleus competence for gene expression.
Asunto(s)
Proteínas Argonautas/genética , Genoma de Protozoos , Proteínas Protozoarias/genética , ARN Protozoario/genética , ARN Interferente Pequeño/genética , Tetrahymena/genética , Proteínas Argonautas/metabolismo , Cromosomas , ADN Protozoario/genética , ADN Protozoario/metabolismo , Reordenamiento Génico , Macronúcleo/genética , Macronúcleo/metabolismo , Micronúcleo Germinal/genética , Micronúcleo Germinal/metabolismo , Proteínas Protozoarias/metabolismo , ARN Protozoario/metabolismo , ARN Interferente Pequeño/metabolismo , Reproducción Asexuada/genética , Tetrahymena/crecimiento & desarrollo , Tetrahymena/metabolismoRESUMEN
The role of many enzymes extends beyond their dedicated catalytic activity by fulfilling important cellular functions in a catalysis-independent fashion. In this aspect, little is known about 3'-end RNA-modifying enzymes that belong to the class of nucleotidyl transferases. Among these are noncanonical poly(A) polymerases, a group of evolutionarily conserved enzymes that are critical for gene expression regulation, by adding adenosines to the 3'-end of RNA targets. In this study, we investigate whether the functions of the cytoplasmic poly(A) polymerase (cytoPAP) GLD-2 in C. elegans germ cells exclusively depend on its catalytic activity. To this end, we analyzed a specific missense mutation affecting a conserved amino acid in the catalytic region of GLD-2 cytoPAP. Although this mutated protein is expressed to wild-type levels and incorporated into cytoPAP complexes, we found that it cannot elongate mRNA poly(A) tails efficiently or promote GLD-2 target mRNA abundance. Furthermore, germ cell defects in animals expressing this mutant protein strongly resemble those lacking the GLD-2 protein altogether, arguing that only the polyadenylation activity of GLD-2 is essential for gametogenesis. In summary, we propose that all known molecular and biological functions of GLD-2 depend on its enzymatic activity, demonstrating that polyadenylation is the key mechanism of GLD-2 functionality. Our findings highlight the enzymatic importance of noncanonical poly(A) polymerases and emphasize the pivotal role of poly(A) tail-centered cytoplasmic mRNA regulation in germ cell biology.
Asunto(s)
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/metabolismo , Regulación de la Expresión Génica , Poli A/metabolismo , Polinucleotido Adenililtransferasa/metabolismo , Procesamiento Postranscripcional del ARN , Secuencia de Aminoácidos , Animales , Animales Modificados Genéticamente , Caenorhabditis elegans/genética , Caenorhabditis elegans/crecimiento & desarrollo , Proteínas de Caenorhabditis elegans/genética , Mutación Missense/genética , Poliadenilación , Polinucleotido Adenililtransferasa/genética , Estabilidad del ARN , ARN Mensajero/metabolismo , Alineación de SecuenciaRESUMEN
The life cycle of flowering plants alternates between two heteromorphic generations: a diploid sporophytic generation and a haploid gametophytic generation. During the development of the plant reproductive lineages - the germlines - typically, single sporophytic (somatic) cells in the flower become committed to undergo meiosis. The resulting spores subsequently develop into highly polarized and differentiated haploid gametophytes that harbour the gametes. Recent studies have provided insights into the genetic basis and regulatory programs underlying cell specification and the acquisition of reproductive fate during both sexual reproduction and asexual (apomictic) reproduction. As we review here, these recent advances emphasize the importance of transcriptional, translational and post-transcriptional regulation, and the role of epigenetic regulatory pathways and hormonal activity.
Asunto(s)
Linaje de la Célula/fisiología , Epigénesis Genética/fisiología , Regulación del Desarrollo de la Expresión Génica/fisiología , Regulación de la Expresión Génica de las Plantas/fisiología , Células Germinativas de las Plantas/crecimiento & desarrollo , Meiosis/fisiología , Desarrollo de la Planta/fisiología , Plantas/genética , Polaridad Celular/fisiología , Gametogénesis/fisiología , Reproducción/fisiologíaRESUMEN
Cytoplasmic polyadenylation drives the translational activation of specific mRNAs in early metazoan development and is performed by distinct complexes that share the same catalytic poly(A)-polymerase subunit, GLD-2. The activity and specificity of GLD-2 depend on its binding partners. In Caenorhabditis elegans, GLD-2 promotes spermatogenesis when bound to GLD-3 and oogenesis when bound to RNP-8. GLD-3 and RNP-8 antagonize each other and compete for GLD-2 binding. Following up on our previous mechanistic studies of GLD-2-GLD-3, we report here the 2.5 Å resolution structure and biochemical characterization of a GLD-2-RNP-8 core complex. In the structure, RNP-8 embraces the poly(A)-polymerase, docking onto several conserved hydrophobic hotspots present on the GLD-2 surface. RNP-8 stabilizes GLD-2 and indirectly stimulates polyadenylation. RNP-8 has a different amino-acid sequence and structure as compared to GLD-3. Yet, it binds the same surfaces of GLD-2 by forming alternative interactions, rationalizing the remarkable versatility of GLD-2 complexes.
Asunto(s)
Proteínas de Caenorhabditis elegans/química , Caenorhabditis elegans/enzimología , Polinucleotido Adenililtransferasa/metabolismo , Proteínas de Unión al ARN/química , Ribonucleoproteínas/química , Animales , Proteínas de Caenorhabditis elegans/fisiología , Cristalografía por Rayos X , Polinucleotido Adenililtransferasa/química , Polinucleotido Adenililtransferasa/fisiología , Conformación Proteica , Proteínas de Unión al ARN/fisiología , Ribonucleoproteínas/fisiologíaRESUMEN
Dead-end1 (Dnd1) expression is restricted to the vertebrate germline where it is believed to activate translation of messenger RNAs (mRNAs) required to protect and promote that unique lineage. Nanos1 is one such germline mRNA whose translation is blocked by a secondary mRNA structure within the open reading frame (ORF). Dnd1 contains a canonical RNA recognition motif (RRM1) in its N-terminus but also contains a less conserved RRM2. Here we provide a mechanistic picture of the nanos1 mRNA-Dnd1 interaction in the Xenopus germline. We show that RRM1, but not RRM2, is required for binding nanos1. Similar to the zebrafish homolog, Xenopus Dnd1 possesses ATPase activity. Surprisingly, this activity appears to be within the RRM2, different from the C-terminal region where it is found in zebrafish. More importantly, we show that RRM2 is required for nanos1 translation and germline survival. Further, Dnd1 functions as a homodimer and binds nanos1 mRNA just downstream of the secondary structure required for nanos1 repression. We propose a model in which the RRM1 is required to bind nanos1 mRNA while the RRM2 is required to promote translation through the action of ATPase. Dnd1 appears to use RRMs to mimic the function of helicases.
Asunto(s)
Modelos Biológicos , Biosíntesis de Proteínas , ARN Helicasas , ARN Mensajero , Proteínas de Unión al ARN , Proteínas Represoras , Proteínas de Xenopus , Animales , Dominios Proteicos , ARN Helicasas/química , ARN Helicasas/genética , ARN Helicasas/metabolismo , Motivo de Reconocimiento de ARN , ARN Mensajero/química , ARN Mensajero/genética , ARN Mensajero/metabolismo , Proteínas de Unión al ARN/química , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Proteínas Represoras/biosíntesis , Proteínas Represoras/química , Proteínas Represoras/genética , Proteínas de Xenopus/biosíntesis , Proteínas de Xenopus/química , Proteínas de Xenopus/genética , Proteínas de Xenopus/metabolismo , Xenopus laevisRESUMEN
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.
Asunto(s)
Caenorhabditis elegans/embriología , Quinasa de la Caseína II/metabolismo , Diferenciación Celular/genética , Proliferación Celular , Células Germinativas/citología , Células Madre/metabolismo , Secuencia de Aminoácidos , Animales , Anticuerpos/inmunología , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Quinasa de la Caseína II/genética , Células Germinativas/metabolismo , Fosforilación , Interferencia de ARN , ARN Interferente Pequeño , Proteínas de Unión al ARN/genética , Receptores Notch/genética , Receptores Notch/metabolismo , Alineación de Secuencia , Transducción de Señal/genéticaRESUMEN
Post-transcriptional regulatory mechanisms are widely used to control gene expression programs of tissue development and physiology. Controlled 3' poly(A) tail-length changes of mRNAs provide a mechanistic basis of such regulation, affecting mRNA stability and translational competence. Deadenylases are a conserved class of enzymes that facilitate poly(A) tail removal, and their biochemical activities have been mainly studied in the context of single-cell systems. Little is known about the different deadenylases and their biological role in multicellular organisms. In this study, we identify and characterize all known deadenylases of Caenorhabditis elegans, and identify the germ line as tissue that depends strongly on deadenylase activity. Most deadenylases are required for hermaphrodite fertility, albeit to different degrees. Whereas ccr-4 and ccf-1 deadenylases promote germline function under physiological conditions, panl-2 and parn-1 deadenylases are only required under heat-stress conditions. We also show that the Ccr4-Not core complex in nematodes is composed of the two catalytic subunits CCR-4 and CCF-1 and the structural subunit NTL-1, which we find to regulate the stability of CCF-1. Using bulk poly(A) tail measurements with nucleotide resolution, we detect strong deadenylation defects of mRNAs at the global level only in the absence of ccr-4, ccf-1 and ntl-1, but not of panl-2, parn-1 and parn-2. Taken together, this study suggests that the Ccr4-Not complex is the main deadenylase complex in C. elegans germ cells. On the basis of this and as a result of evidence in flies, we propose that the conserved Ccr4-Not complex is an essential component in post-transcriptional regulatory networks promoting animal reproduction.
Asunto(s)
Poli A/genética , ARN Mensajero/genética , Ribonucleasas/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Animales , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Genómica , Células Germinativas , Poli A/metabolismo , ARN Mensajero/metabolismo , Ribonucleasas/genética , Proteínas de Saccharomyces cerevisiae/genética , Factores de TranscripciónRESUMEN
Spermatogonial stem cells (SSCs) are a subset of undifferentiated spermatogonia responsible for ongoing spermatogenesis in mammalian testes. Spermatogonial stem cells arise from morphologically homogeneous prospermatogonia, but growing evidence suggests that only a subset of prospermatogonia develops into the foundational SSC pool. This predicts that subtypes of undifferentiated spermatogonia with discrete mRNA and protein signatures should be distinguishable in neonatal testes. We used single-cell quantitative RT-PCR to examine mRNA levels of 172 genes in individual spermatogonia from 6-day postnatal (P6) mouse testes. Cells enriched from P6 testes using the StaPut or THY1(+) magnetic cell sorting methods exhibited considerable heterogeneity in the abundance of specific germ cell and stem cell mRNAs, segregating into one somatic and three distinct spermatogonial clusters. However, P6 Id4-eGFP(+) transgenic spermatogonia, which are known to be enriched for SSCs, were more homogeneous in their mRNA levels, exhibiting uniform levels for the majority of genes examined (122 of 172). Interestingly, these cells displayed nonuniform (50 of 172) expression of a smaller cohort of these genes, suggesting there is substantial heterogeneity even within the Id4-eGFP(+) population. Further, although immunofluorescence staining largely demonstrated conformity between mRNA and protein levels, some proteins were observed in patterns that were disparate from those detected for the corresponding mRNAs in Id4-eGFP(+) spermatogonia (e.g., Kit, Sohlh2, Stra8), suggesting additional heterogeneity is introduced at the posttranscriptional level. Taken together, these data demonstrate the existence of multiple spermatogonial subtypes in P6 mouse testes and raise the intriguing possibility that these subpopulations may correlate with the development of functionally distinct spermatogenic cell types.
Asunto(s)
Regulación del Desarrollo de la Expresión Génica , Espermatogénesis/genética , Espermatogonias/metabolismo , Testículo/metabolismo , Animales , Masculino , Ratones , ARN Mensajero/genética , ARN Mensajero/metabolismo , Testículo/citologíaRESUMEN
Previously, we analyzed 316 herbal extracts to evaluate their potential nematocidal properties in Caenorhabditis elegans. In this study, our attention was directed towards Torenia sp., resulting in reduced survival and heightened larval arrest/lethality, alongside a noticeable decrease in DAPI-stained bivalent structures and disrupted meiotic progression, thus disrupting developmental processes. Notably, Torenia sp. extracts activated a DNA damage checkpoint response via the ATM/ATR and CHK-1 pathways, hindering germline development. LC-MS analysis revealed 13 compounds in the Torenia sp. extracts, including flavonoids, terpenoids, tanshinones, an analog of resveratrol, iridoids, carotenoids, fatty acids, and alkaloids. Of these, 10 are known for their antitumor activity, suggesting the potential of Torenia species beyond traditional gardening, extending into pharmaceutical and therapeutic applications.