scholarly journals Cellular Analyses of the Mitotic Region in the Caenorhabditis elegans Adult Germ Line

2006 ◽  
Vol 17 (7) ◽  
pp. 3051-3061 ◽  
Author(s):  
Sarah L. Crittenden ◽  
Kimberly A. Leonhard ◽  
Dana T. Byrd ◽  
Judith Kimble
Keyword(s):  
Stem Cells ◽  
Caenorhabditis Elegans ◽  
Germ Cells ◽  
Germ Line ◽  
Germline Stem Cells ◽  
C Elegans ◽  
Brdu Label ◽  
Asymmetric Divisions ◽  
Brdu Labeling ◽  
Cell Niche

The Caenorhabditis elegans germ line provides a model for understanding how signaling from a stem cell niche promotes continued mitotic divisions at the expense of differentiation. Here we report cellular analyses designed to identify germline stem cells within the germline mitotic region of adult hermaphrodites. Our results support several conclusions. First, all germ cells within the mitotic region are actively cycling, as visualized by bromodeoxyuridine (BrdU) labeling. No quiescent cells were found. Second, germ cells in the mitotic region lose BrdU label uniformly, either by movement of labeled cells into the meiotic region or by dilution, probably due to replication. No label-retaining cells were found in the mitotic region. Third, the distal tip cell niche extends processes that nearly encircle adjacent germ cells, a phenomenon that is likely to anchor the distal-most germ cells within the niche. Fourth, germline mitoses are not oriented reproducibly, even within the immediate confines of the niche. We propose that germ cells in the distal-most rows of the mitotic region serve as stem cells and more proximal germ cells embark on the path to differentiation. We also propose that C. elegans adult germline stem cells are maintained by proximity to the niche rather than by programmed asymmetric divisions.

scholarly journals glp-3 Is Required for Mitosis and Meiosis in the Caenorhabditis elegans Germ Line

Genetics ◽  
1997 ◽  
Vol 145 (1) ◽  
pp. 111-121 ◽  
Author(s):  
Lisa C Kadyk ◽  
Eric J Lambie ◽  
Judith Kimble
Keyword(s):  
Caenorhabditis Elegans ◽  
Germ Cells ◽  
Germ Line ◽  
Stem Cell Population ◽  
Phenotypic Characterization ◽  
Loss Of Function ◽  
Dapi Staining ◽  
Cell Cycles ◽  
C Elegans ◽  
Mitosis And Meiosis

The germ line is the only tissue in Caenorhabditis elegans in which a stem cell population continues to divide mitotically throughout life; hence the cell cycles of the germ line and the soma are regulated differently. Here we report the genetic and phenotypic characterization of the glp-3 gene. In animals homozygous for each of five recessive loss-of-function alleles, germ cells in both hermaphrodites and males fail to progress through mitosis and meiosis, but somatic cells appear to divide normally. Germ cells in animals grown at 15° appear by DAPI staining to be uniformly arrested at the G2/M transition with <20 germ cells per gonad on average, suggesting a checkpoint-mediated arrest. In contrast, germ cells in mutant animals grown at 25° frequently proliferate slowly during adulthood, eventually forming small germ lines with several hundred germ cells. Nevertheless, cells in these small germ lines never undergo meiosis. Double mutant analysis with mutations in other genes affecting germ cell proliferation supports the idea that glp-3 may encode a gene product that is required for the mitotic and meiotic cell cycles in the C. elegans germ line.

scholarly journals Regulation of the mitosis/meiosis decision in the Caenorhabditis elegans germline

2003 ◽  
Vol 358 (1436) ◽  
pp. 1359-1362 ◽  
Author(s):  
Sarah L. Crittenden ◽  
Christian R. Eckmann ◽  
Liaoteng Wang ◽  
David S. Bernstein ◽  
Marvin Wickens ◽  
...  
Keyword(s):  
Stem Cells ◽  
Caenorhabditis Elegans ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Germline Stem Cells ◽  
Puf Proteins ◽  
C Elegans ◽  
Transcriptional Regulatory ◽  
Mitotic Proliferation ◽  
Multicellular Organisms

During the development of multicellular organisms, the processes of growth and differentiation are kept in balance to generate and maintain tissues and organs of the correct size, shape and cellular composition. We have investigated the molecular controls of growth and differentiation in the Caenorhabditis elegans germline. A single somatic cell, called the distal tip cell, promotes mitotic proliferation in the adjacent germline by GLP–1/Notch signalling. Within the germline, the decisions between mitosis and meiosis and between spermatogenesis and oogenesis are controlled by a group of conserved RNA regulators. FBF, a member of the PUF (for Pumilio and FBF) family of RNA–binding proteins, promotes mitosis by repressing gld–1 mRNA activity; the GLD–1, GLD–2, GLD–3 and NOS–3 proteins promote entry into meiosis by regulating mRNAs that remain unknown. The regulatory balance between opposing FBF and GLD activities is crucial for controlling the extent of germline proliferation. PUF proteins regulate germline stem cells in both Drosophila and C. elegans and are localized to germline stem cells of the mammalian testis. Therefore, this post–transcriptional regulatory switch may be an ancient mechanism for controlling maintenance of stem cells versus differentiation.

scholarly journals Systemic regulation of mitochondria by germline proteostasis prevents protein aggregation in the soma of C. elegans

2021 ◽  
Vol 7 (26) ◽  
pp. eabg3012
Author(s):  
Giuseppe Calculli ◽  
Hyun Ju Lee ◽  
Koning Shen ◽  
Uyen Pham ◽  
Marija Herholz ◽  
...  
Keyword(s):  
Stem Cells ◽  
Protein Aggregation ◽  
Germ Line ◽  
Wnt Signaling Pathway ◽  
Germline Stem Cells ◽  
C Elegans ◽  
Unfolded Protein ◽  
Somatic Tissues ◽  
Intracellular Changes ◽  
The Unfolded Protein Response

Protein aggregation causes intracellular changes in neurons, which elicit signals to modulate proteostasis in the periphery. Beyond the nervous system, a fundamental question is whether other organs also communicate their proteostasis status to distal tissues. Here, we examine whether proteostasis of the germ line influences somatic tissues. To this end, we induce aggregation of germline-specific PGL-1 protein in germline stem cells of Caenorhabditis elegans. Besides altering the intracellular mitochondrial network of germline cells, PGL-1 aggregation also reduces the mitochondrial content of somatic tissues through long-range Wnt signaling pathway. This process induces the unfolded protein response of the mitochondria in the soma, promoting somatic mitochondrial fragmentation and aggregation of proteins linked with neurodegenerative diseases such as Huntington’s and amyotrophic lateral sclerosis. Thus, the proteostasis status of germline stem cells coordinates mitochondrial networks and protein aggregation through the organism.

scholarly journals CENP-C regulates centromere assembly, asymmetry and epigenetic age in Drosophila germline stem cells

2020 ◽  
Author(s):  
Ben L Carty ◽  
Anna A Dattoli ◽  
Elaine M Dunleavy
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Cell Fate ◽  
Germ Line ◽  
Asymmetric Distribution ◽  
Germline Stem Cells ◽  
Daughter Cells ◽  
Sister Chromatids ◽  
Asymmetric Divisions ◽  
Centromere Assembly

AbstractGermline stem cells divide asymmetrically to produce one new daughter stem cell and one daughter cell that will subsequently undergo meiosis and differentiate to generate the mature gamete. The silent sister hypothesis proposes that in asymmetric divisions, the selective inheritance of sister chromatids carrying specific epigenetic marks between stem and daughter cells impacts cell fate. To facilitate this selective inheritance, the hypothesis specifically proposes that the centromeric region of each sister chromatid is distinct. In Drosophila germ line stem cells (GSCs), it has recently been shown that the centromeric histone CENP-A (called CID in flies) - the epigenetic determinant of centromere identity - is asymmetrically distributed between sister chromatids. In these cells, CID deposition occurs in G2 phase such that sister chromatids destined to end up in the stem cell harbour more CENP-A, assemble more kinetochore proteins and capture more spindle microtubules. These results suggest a potential mechanism of ‘mitotic drive’ that might bias chromosome segregation. Here we report that the inner kinetochore protein CENP-C, is required for the assembly of CID in G2 phase in GSCs. Moreover, CENP-C is required to maintain a normal asymmetric distribution of CID between stem and daughter cells. In addition, we find that CID is lost from centromeres in aged GSCs and that a reduction in CENP-C accelerates this loss. Finally, we show that CENP-C depletion in GSCs disrupts the balance of stem and daughter cells in the ovary, shifting GSCs toward a self-renewal tendency. Ultimately, we provide evidence that centromere assembly and maintenance via CENP-C is required to sustain asymmetric divisions in female Drosophila GSCs.

scholarly journals C. elegans germ cells divide and differentiate along a folded epithelium

2018 ◽  
Author(s):  
Hannah S. Seidel ◽  
Tilmira A. Smith ◽  
Jessica K. Evans ◽  
Jarred Q. Stamper ◽  
Thomas G. Mast ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Germ Cells ◽  
Cell Model ◽  
Three Dimensional ◽  
3D Models ◽  
Germline Stem Cells ◽  
C Elegans ◽  
Stem Cell Regulation ◽  
Stem Cell Model

AbstractKnowing how stem cells and their progeny are positioned within their tissues is essential for understanding their regulation. One paradigm for stem cell regulation is the C. elegans germline, which is maintained by a pool of germline stem cells in the distal gonad, in a region known as the ‘progenitor zone’. The C. elegans germline is widely used as a stem cell model, but the cellular architecture of the progenitor zone has been unclear. Here we characterize this architecture by creating virtual 3D models of the progenitor zone in both sexes. We show that the progenitor zone in adult hermaphrodites is essentially a folded epithelium. The progenitor zone in males is not folded. Analysis of germ cell division shows that daughter cells are born side-by-side along the surface of the epithelium. Analysis of a key regulator driving differentiation, GLD-1, shows that germ cells in hermaphrodites differentiate along the path of the folded epithelium, with previously described “steps” in GLD-1 expression corresponding to germline folds. Our study provides a three-dimensional view of how C. elegans germ cells progress from stem cell to overt differentiation, with critical implications for regulators driving this transition.

scholarly journals CENP-C functions in centromere assembly, the maintenance of CENP-A asymmetry and epigenetic age in Drosophila germline stem cells

PLoS Genetics ◽  
2021 ◽  
Vol 17 (5) ◽  
pp. e1009247
Author(s):  
Ben L. Carty ◽  
Anna A. Dattoli ◽  
Elaine M. Dunleavy
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Cell Fate ◽  
Germ Line ◽  
Asymmetric Distribution ◽  
Germline Stem Cells ◽  
Daughter Cells ◽  
Sister Chromatids ◽  
Asymmetric Divisions ◽  
Centromere Assembly

Germline stem cells divide asymmetrically to produce one new daughter stem cell and one daughter cell that will subsequently undergo meiosis and differentiate to generate the mature gamete. The silent sister hypothesis proposes that in asymmetric divisions, the selective inheritance of sister chromatids carrying specific epigenetic marks between stem and daughter cells impacts cell fate. To facilitate this selective inheritance, the hypothesis specifically proposes that the centromeric region of each sister chromatid is distinct. In Drosophila germ line stem cells (GSCs), it has recently been shown that the centromeric histone CENP-A (called CID in flies)—the epigenetic determinant of centromere identity—is asymmetrically distributed between sister chromatids. In these cells, CID deposition occurs in G2 phase such that sister chromatids destined to end up in the stem cell harbour more CENP-A, assemble more kinetochore proteins and capture more spindle microtubules. These results suggest a potential mechanism of ‘mitotic drive’ that might bias chromosome segregation. Here we report that the inner kinetochore protein CENP-C, is required for the assembly of CID in G2 phase in GSCs. Moreover, CENP-C is required to maintain a normal asymmetric distribution of CID between stem and daughter cells. In addition, we find that CID is lost from centromeres in aged GSCs and that a reduction in CENP-C accelerates this loss. Finally, we show that CENP-C depletion in GSCs disrupts the balance of stem and daughter cells in the ovary, shifting GSCs toward a self-renewal tendency. Ultimately, we provide evidence that centromere assembly and maintenance via CENP-C is required to sustain asymmetric divisions in female Drosophila GSCs.

scholarly journals Conservation of glp-1 Regulation and Function in Nematodes

Genetics ◽  
2001 ◽  
Vol 157 (2) ◽  
pp. 639-654
Author(s):  
David Rudel ◽  
Judith Kimble
Keyword(s):  
Stem Cells ◽  
Phylogenetic Analysis ◽  
Caenorhabditis Elegans ◽  
Sequence Analysis ◽  
Regulatory Elements ◽  
Germline Stem Cells ◽  
Biological Functions ◽  
C Elegans ◽  
Caenorhabditis Species ◽  
And Function

Abstract The Caenorhabditis elegans (Ce) glp-1 gene encodes a Notch-like receptor. We have cloned glp-1 from C. briggsae (Cb) and C. remanei (Cr), two Caenorhabditis species that have diverged from C. elegans by roughly 20–40 million years. By sequence analysis, we find that the Cb-GLP-1 and Cr-GLP-1 proteins have retained the same motif architecture as Ce-GLP-1, including number of domains. In addition, two regions (CC-linker and regions flanking the ANK repeats) are as highly conserved as regions previously recognized as essential for signaling (e.g., ANK repeats). Phylogenetic analysis of glp-1 sequences suggests a C. briggsae/C. remanei clade with C. elegans as a sister taxon. Using RNAi to test biological functions, we find that Ce-glp-1, Cb-glp-1, and Cr-glp-1 are all required for proliferation of germline stem cells and for specifying blastomere fates in the embryo. In addition, certain biological roles of Cb-glp-1, e.g., in the vulva, have diverged from those of Ce-glp-1 and Cr-glp-1, suggesting a change in either regulation or function of the Cb-glp-1 gene during evolution. Finally, the regulation of glp-1 mRNA, previously analyzed for Ce-glp-1, is conserved in Cb-glp-1, and we identify conserved 3′ UTR sequences that may serve as regulatory elements.

scholarly journals Stem-cell niche self-restricts the signaling range via receptor-ligand degradation

2018 ◽  
Author(s):  
Sophia Ladyzhets ◽  
Matthew Antel ◽  
Taylor Simao ◽  
Nathan Gasek ◽  
Mayu Inaba
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Germ Cells ◽  
Stem Cell Niche ◽  
Short Range ◽  
Receptor Interaction ◽  
Germline Stem Cells ◽  
Dual Roles ◽  
Ectopic Activation ◽  
Cell Niche

AbstractStem-cell niche signaling is short-range in nature, such that only stem cells but not their differentiating progeny experience self-renewing signals. At the apical tip of the Drosophila testes, 8 to 10 germline stem cells (GSCs) surround the hub, a cluster of somatic cells that function as the major component of the stem cell niche. We have shown that GSCs form microtubule-based nanotubes (MT-nanotubes), which project into the hub cells, serving as the platform for niche signal reception: the receptor Tkv expressed by GSCs localizes to the surface of MT-nanotubes, where it receives the hub-derived ligand Decapentaplegic (Dpp), ensuring the reception of the ligand specifically by stem cells but not by differentiating cells.Here we show that receptor (Tkv)-ligand (Dpp) interaction at the surface of MT-nanotubes serves a second purpose of dampening the niche signaling: we found that the receptor Tkv and the ligand Dpp are internalized into hub cells and are degraded in the hub cell lysosomes. Perturbation of hub lysosomal function or MT-nanotube formation leads to excess receptor retention within germ cells as well as excess Dpp that diffuses out of the hub, leading to ectopic activation of niche signal in differentiating germ cells. Our results demonstrate that MT-nanotubes plays dual roles in ensuring the short-range nature of the niche signaling by 1) providing exclusive interphase of the niche ligand-receptor interaction and 2) limiting the amount of available ligand-receptor via their degradation.

scholarly journals A Genome-Wide RNAi Screen for Enhancers of a Germline Tumor Phenotype Caused by Elevated GLP-1/Notch Signaling in Caenorhabditis elegans

2020 ◽  
Vol 10 (12) ◽  
pp. 4323-4334
Author(s):  
Diana Dalfó ◽  
Yanhui Ding ◽  
Qifei Liang ◽  
Alex Fong ◽  
Patricia Giselle Cipriani ◽  
...  
Keyword(s):  
Stem Cells ◽  
Caenorhabditis Elegans ◽  
Germ Cells ◽  
Germ Line ◽  
Tumor Formation ◽  
Permissive Temperature ◽  
Germline Development ◽  
Link Type ◽  
Somatic Gonad

Stem cells are tightly controlled in vivo. Both the balance between self-renewal and differentiation and the rate of proliferation are often regulated by multiple factors. The Caenorhabditis elegans hermaphrodite germ line provides a simple and accessible system for studying stem cells in vivo. In this system, GLP-1/Notch activity prevents the differentiation of distal germ cells in response to ligand production from the nearby distal tip cell, thereby supporting a stem cell pool. However, a delay in germline development relative to somatic gonad development can cause a pool of undifferentiated germ cells to persist in response to alternate Notch ligands expressed in the proximal somatic gonad. This pool of undifferentiated germ cells forms a proximal tumor that, in adulthood, blocks the oviduct. This type of “latent niche”-driven proximal tumor is highly penetrant in worms bearing the temperature-sensitive weak gain-of-function mutation glp-1(ar202) at the restrictive temperature. At the permissive temperature, few worms develop tumors. Nevertheless, several interventions elevate the penetrance of proximal tumor formation at the permissive temperature, including reduced insulin signaling or the ablation of distal-most sheath cells. To systematically identify genetic perturbations that enhance proximal tumor formation, we sought genes that, upon RNAi depletion, elevate the percentage of worms bearing proximal germline tumors in glp-1(ar202) at the permissive temperature. We identified 43 genes representing a variety of functional classes, the most enriched of which is “translation”. Some of these genes also influence the distal germ line, and some are conserved genes for which genetic interactions with Notch were not previously known in this system.

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