scholarly journals Reduction of Derlin activity suppresses Notch-dependent tumours in the C. elegans germ line

2021 ◽  
Author(s):  
Ramya Singh ◽  
Ryan Smit ◽  
Xin Wang ◽  
Chris Wang ◽  
Hilary Racher ◽  
...  
Keyword(s):  
Stem Cell ◽  
Er Stress ◽  
Notch Signaling ◽  
Germ Line ◽  
Notch Receptor ◽  
Loss Of Function ◽  
Gain Of Function ◽  
Self Renewal ◽  
C Elegans ◽  
Proliferation Suppression

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 tumor 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.

scholarly journals Reduction of Derlin activity suppresses Notch-dependent tumours in the C. elegans germ line

PLoS Genetics ◽  
2021 ◽  
Vol 17 (9) ◽  
pp. e1009687
Author(s):  
Ramya Singh ◽  
Ryan B. Smit ◽  
Xin Wang ◽  
Chris Wang ◽  
Hilary Racher ◽  
...  
Keyword(s):  
Stem Cell ◽  
Er Stress ◽  
Notch Signaling ◽  
Germ Line ◽  
Notch Signaling Pathway ◽  
Notch Receptor ◽  
Loss Of Function ◽  
Gain Of Function ◽  
Self Renewal ◽  
Proliferation Suppression

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.

scholarly journals Progression from a stem cell–like state to early differentiation in the C. elegans germ line

2010 ◽  
Vol 107 (5) ◽  
pp. 2048-2053 ◽  
Author(s):  
Olivier Cinquin ◽  
Sarah L. Crittenden ◽  
Dyan E. Morgan ◽  
Judith Kimble
Keyword(s):  
Stem Cell ◽  
Germ Cells ◽  
Cell Biology ◽  
Germ Line ◽  
Stem Cell Biology ◽  
Self Renewal ◽  
Early Differentiation ◽  
C Elegans ◽  
Stem Cell Maintenance ◽  
System A

Controls of stem cell maintenance and early differentiation are known in several systems. However, the progression from stem cell self-renewal to overt signs of early differentiation is a poorly understood but important problem in stem cell biology. The Caenorhabditis elegans germ line provides a genetically defined model for studying that progression. In this system, a single-celled mesenchymal niche, the distal tip cell (DTC), employs GLP-1/Notch signaling and an RNA regulatory network to balance self-renewal and early differentiation within the “mitotic region,” which continuously self-renews while generating new gametes. Here, we investigate germ cells in the mitotic region for their capacity to differentiate and their state of maturation. Two distinct pools emerge. The “distal pool” is maintained by the DTC in an essentially uniform and immature or “stem cell–like” state; the “proximal pool,” by contrast, contains cells that are maturing toward early differentiation and are likely transit-amplifying cells. A rough estimate of pool sizes is 30–70 germ cells in the distal immature pool and ≈150 in the proximal transit-amplifying pool. We present a simple model for how the network underlying the switch between self-renewal and early differentiation may be acting in these two pools. According to our model, the self-renewal mode of the network maintains the distal pool in an immature state, whereas the transition between self-renewal and early differentiation modes of the network underlies the graded maturation of germ cells in the proximal pool. We discuss implications of this model for controls of stem cells more broadly.

Notch Signaling Is Necessary and Sufficient for Runx1-Dependent Stem Cell Induction in the Embryonic Aorta-Gonad-Mesonephros (AGM) Region.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4161-4161
Author(s):  
Caroline Erter Burns ◽  
Leonard I. Zon
Keyword(s):  
Stem Cell ◽  
Notch Signaling ◽  
Cell Fate ◽  
Notch Pathway ◽  
Notch Receptor ◽  
Dorsal Aorta ◽  
Loss Of Function ◽  
Cardinal Vein ◽  
Hematopoietic Stem

Abstract Vertebrate hematopoiesis can be divided into two embryonic phases: a short primitive wave predominantly generating erythrocytes and a definitive (fetal/adult) wave producing long-term hematopoietic stem cells (HSCs). The definitive wave occurs in the embryonic aorta-gonad-mesonephros (AGM) region through the asymmetric induction of HSCs from the ventral, but not dorsal, aortic endothelial wall. Since Notch signaling is critical for orchestrating a variety of developmental cell fate choices from invertebrates to humans and has been implicated in affecting the differentiation of some hematopoietic lineages, we analyzed whether the Notch pathway regulates definitive HSC induction in vivo. The zebrafish mutant mindbomb harbors a mutation in an essential E3 ligase that ubiquitylates Delta, which in turn allows the Notch intercellular domain to be released and activate downstream target gene transcription. Thus, in the absence of Mindbomb function Notch signaling does not occur. We found that although mindbomb mutants show normal primitive hematopoiesis, definitive c-myb and runx1 HSC expression is lacking. Since embryos injected with synthetic morpholinos designed to inhibit proper splicing of runx1 RNA ( runx morphants) show the same hematopoietic phenotype as mindbomb mutants, we next addressed the epistatic relationship between notch and runx1 using classic gain-of-function and loss-of-function analyses. In runx1 morphants expression of a notch receptor, notch3, and a delta ligand, deltaC, in the developing dorsal aorta was normal. Moreover, injection of runx1 RNA rescued HSCs in the AGM of mindbomb mutants. Together, these results suggest that Runx1 functions downstream of Notch in promoting HSC fate. We next analyzed whether a constitutively activated form of Notch (NICD) is sufficient for HSC specification in the AGM using an inducible binary transgenic system. Zebrafish carrying the heat-shock promoter driving the activator gal4 were mated to animals carrying 6 gal4 -responsive tandem upstream activating sequences (UAS) driving NICD. At the 10 somite-stage the embryos were heat-shocked at 37°C for 1 hour to activate NICD throughout the double transgenic animals. Surprisingly, expression of both HSC markers, c-myb and runx1, were expanded from their normal restricted domain in the ventral endothelium to the entire circumference of the dorsal aorta. Most interestingly, the presence of ectopic c-myb and runx1 transcripts were observed in the developing post-cardinal vein, a vessel that normally does not produce HSCs. These data imply that activation of the Notch pathway generates increased numbers of HSCs in vivo. When runx1 RNA is injected into wild-type embryos a similar expansion of c-myb transcripts is seen throughout the entire dorsal aorta and post-cardinal vein, further indicating that Runx1 functions downstream of Notch in HSC induction. In summary, discovery of the molecular programs essential and sufficient for fetal/adult hematopoietic ontogeny will lead to a further understanding of the physiologic and pathologic processes regulating stem cell homeostasis and translate into more effective therapies for blood disorders.

scholarly journals Discovery of two GLP-1/Notch target genes that account for the role of GLP-1/Notch signaling in stem cell maintenance

2014 ◽  
Vol 111 (10) ◽  
pp. 3739-3744 ◽  
Author(s):  
Aaron M. Kershner ◽  
Heaji Shin ◽  
Tyler J. Hansen ◽  
Judith Kimble
Keyword(s):  
Stem Cell ◽  
Notch Signaling ◽  
Target Genes ◽  
Germ Line ◽  
Intercellular Signaling ◽  
Self Renewal ◽  
Stem Cell Maintenance ◽  
Per Se ◽  
Critical Link

A stem cell’s immediate microenvironment creates an essential “niche” to maintain stem cell self-renewal. Many niches and their intercellular signaling pathways are known, but for the most part, the key downstream targets of niche signaling remain elusive. Here, we report the discovery of two GLP-1/Notch target genes, lst-1 (lateral signaling target) and sygl-1 (synthetic Glp), that function redundantly to maintain germ-line stem cells (GSCs) in the nematode Caenorhabditis elegans. Whereas lst-1 and sygl-1 single mutants appear normal, lst-1 sygl-1 double mutants are phenotypically indistinguishable from glp-1/Notch mutants. Multiple lines of evidence demonstrate that GLP-1/Notch signaling activates lst-1 and sygl-1 expression in GSCs within the niche. Therefore, these two genes fully account for the role of GLP-1/Notch signaling in GSC maintenance. Importantly, lst-1 and sygl-1 are not required for GLP-1/Notch signaling per se. We conclude that lst-1 and sygl-1 forge a critical link between Notch signaling and GSC maintenance.

scholarly journals Intermittent Stem Cell Cycling Balances Self-Renewal and Senescence of the C. elegans Germ Line

PLoS Genetics ◽  
2016 ◽  
Vol 12 (4) ◽  
pp. e1005985 ◽  
Author(s):  
Amanda Cinquin ◽  
Michael Chiang ◽  
Adrian Paz ◽  
Sam Hallman ◽  
Oliver Yuan ◽  
...  
Keyword(s):  
Stem Cell ◽  
Germ Line ◽  
Self Renewal ◽  
C Elegans ◽  
Cell Cycling

scholarly journals A PUF hub drives self-renewal in C. elegans germline stem cells

2019 ◽  
Author(s):  
Kimberly A. Haupt ◽  
Kimberley T. Law ◽  
Amy L. Enright ◽  
Charlotte R. Kanzler ◽  
Heaji Shin ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Notch Signaling ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Germline Stem Cells ◽  
Null Mutant ◽  
Self Renewal ◽  
Puf Proteins ◽  
C Elegans

ABSTRACTStem cell regulation relies on extrinsic signaling from a niche plus intrinsic factors that respond and drive self-renewal within stem cells. A priori, loss of niche signaling and loss of the intrinsic self-renewal factors might be expected to have equivalent stem cell defects. Yet this simple prediction has not been borne out for most stem cells, including C. elegans germline stem cells (GSCs). The central regulators of C. elegans GSCs include extrinsically-acting GLP-1/Notch signaling from the niche, intrinsically-acting RNA binding proteins in the PUF family, termed FBF-1 and FBF-2 (collectively FBF), and intrinsically-acting PUF partner proteins that are direct Notch targets. Abrogation of either GLP-1/Notch signaling or its targets yields an earlier and more severe GSC defect than loss of FBF-1 and FBF-2, suggesting that additional intrinsic regulators must exist. Here, we report that those missing regulators are two additional PUF proteins, PUF-3 and PUF-11. Remarkably, an fbf-1 fbf-2; puf-3 puf-11 quadruple null mutant has a GSC defect virtually identical to that of a glp-1/Notch null mutant. PUF-3 and PUF-11 both affect GSC maintenance; both are expressed in GSCs; and epistasis experiments place them at the same position as FBF within the network. Therefore, action of PUF-3 and PUF-11 explains the milder GSC defect in fbf-1 fbf-2 mutants. We conclude that a “PUF hub”, comprising four PUF proteins and two PUF partners, constitutes the intrinsic self-renewal node of the C. elegans GSC RNA regulatory network. Discovery of this hub underscores the significance of PUF RNA-binding proteins as key regulators of stem cell maintenance.

scholarly journals A Genetic Screen for Novel Components of the Notch Signaling Pathway During Drosophila Bristle Development

Genetics ◽  
1998 ◽  
Vol 150 (1) ◽  
pp. 211-220 ◽  
Author(s):  
Masahiro J Go ◽  
Spyros Artavanis-Tsakonas
Keyword(s):  
Notch Signaling ◽  
Cell Fate ◽  
Genetic Modifier ◽  
Notch Pathway ◽  
Central Element ◽  
Notch Signaling Pathway ◽  
Notch Receptor ◽  
Loss Of Function ◽  
Gain Of Function ◽  
Signaling Mechanism

Abstract The Notch receptor is the central element in a cell signaling mechanism controlling a broad spectrum of cell fate choices. Genetic modifier screens in Drosophila and subsequent molecular studies have identified several Notch pathway components, but the biochemical nature of signaling is still elusive. Here, we report the results of a genetic modifier screen of the bristle phenotype of a gain-of-function Notch allele, Abruptex16. Abruptex mutations interfere with lateral inhibition/specification events that control the segregation of epidermal and sensory organ precursor lineages, thus inhibiting bristle formation. Mutations that reduce Notch signaling suppress this phenotype. This screen of approximately 50,000 flies led to the identification of a small number of dominant suppressors in seven complementation groups. These include known components in the pathway, Notch, mastermind, Delta, and Hairless, as well as two novel mutations. The first, A122, appears to interact with Notch only during bristle development. The other, M285, displays extensive genetic interactions with the Notch pathway elements and appears, in general, capable of suppressing Notch gain-of-function phenotypes while enhancing Notch loss-of-function phenotypes, suggesting that it plays an important role in Notch signaling.

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