MES-1, a protein required for unequal divisions of the germline in early C. elegans embryos, resembles receptor tyrosine kinases and is localized to the boundary between the germline and gut cells

Development ◽  
2000 ◽  
Vol 127 (20) ◽  
pp. 4419-4431 ◽  
Author(s):  
L.A. Berkowitz ◽  
S. Strome
Keyword(s):  
Cell Fate ◽  
Tyrosine Kinases ◽  
Spatial Organization ◽  
Function Analysis ◽  
Primordial Germ Cell ◽  
P Granules ◽  
C Elegans ◽  
Autonomous Function ◽  
Germ Granules ◽  
A Cell

During Caenorhabditis elegans embryogenesis the primordial germ cell, P(4), is generated via a series of unequal divisions. These divisions produce germline blastomeres (P(1), P(2), P(3), P(4)) that differ from their somatic sisters in their size, fate and cytoplasmic content (e.g. germ granules). mes-1 mutant embryos display the striking phenotype of transformation of P(4) into a muscle precursor, like its somatic sister. A loss of polarity in P(2) and P(3) cell-specific events underlies the Mes-1 phenotype. In mes-1 embryos, P(2) and P(3) undergo symmetric divisions and partition germ granules to both daughters. This paper shows that mes-1 encodes a receptor tyrosine kinase-like protein, though it lacks several residues conserved in all kinases and therefore is predicted not to have kinase activity. Immunolocalization analysis shows that MES-1 is present in four- to 24-cell embryos, where it is localized in a crescent at the junction between the germline cell and its neighboring gut cell. This is the region of P(2) and P(3) to which the spindle and P granules must move to ensure normal division asymmetry and cytoplasmic partitioning. Indeed, during early stages of mitosis in P(2) and P(3), one centrosome is positioned adjacent to the MES-1 crescent. Staining of isolated blastomeres demonstrated that MES-1 was present in the membrane of the germline blastomeres, consistent with a cell-autonomous function. Analysis of MES-1 distribution in various cell-fate and patterning mutants suggests that its localization is not dependent on the correct fate of either the germline or the gut blastomere but is dependent upon correct spatial organization of the embryo. Our results suggest that MES-1 directly positions the developing mitotic spindle and its associated P granules within P(2) and P(3), or provides an orientation signal for P(2)- and P(3)-specific events.

scholarly journals Recruitment of mRNAs to P granules by gelation with intrinsically-disordered proteins

2019 ◽  
Author(s):  
Chih-Yung S. Lee ◽  
Andrea Putnam ◽  
Tu Lu ◽  
Shuaixin He ◽  
John Paul T. Ouyang ◽  
...  
Keyword(s):  
Cell Fate ◽  
Intrinsically Disordered Proteins ◽  
Intrinsically Disordered Protein ◽  
Disordered Proteins ◽  
P Granules ◽  
C Elegans ◽  
Rna Granules ◽  
Intrinsically Disordered ◽  
Cytoplasmic Rna ◽  
Germ Granules

AbstractAnimals with germ plasm assemble cytoplasmic RNA granules (germ granules) that segregate with the embryonic germ lineage. How germ granules assemble and recruit RNA is not well understood. Here we characterize the assembly and RNA composition of the germ (P) granules of C. elegans. ∼500 maternal mRNAs are recruited into P granules by a sequence independent mechanism that favors mRNAs with low ribosome coverage. Translational activation correlates temporally with P granule exit for two mRNAs that code for germ cell fate regulators. mRNAs are recruited into the granules by MEG-3, an intrinsically disordered protein that condenses with RNA to form nanoscale gels. Our observations reveal parallels between germ granules and stress granules and suggest that cytoplasmic RNA granules are reversible super-assemblies of nanoscale RNA-protein gel condensates.

scholarly journals Signal co-operation between integrins and other receptor systems

2009 ◽  
Vol 418 (3) ◽  
pp. 491-506 ◽  
Author(s):  
Charles H. Streuli ◽  
Nasreen Akhtar
Keyword(s):  
Cell Fate ◽  
Tyrosine Kinases ◽  
Spatial Organization ◽  
Growth Factor Receptor ◽  
Cellular Processes ◽  
Extracellular Signals ◽  
Β1 Integrins ◽  
Α6β4 Integrin ◽  
Epidermal Growth ◽  
Adhesive Interactions

The multicellular nature of metazoans means that all cellular processes need to be tuned by adhesive interactions between cells and their local microenvironment. The spatial organization of cells within tissues requires sophisticated networks of extracellular signals to control their survival and proliferation, movements and positioning, and differentiated function. These cellular characteristics are mediated by multiple inputs from adhesion systems in combination with soluble and developmental signals. In the present review we explore how one class of adhesion receptor, the integrins, co-operate with other types of receptor to control diverse aspects of cell fate. In particular we discuss: (i) how β3 and β1 integrins work together with growth factors to control angiogenesis; (ii) how α6β4 integrin co-operates with receptor tyrosine kinases in normal epithelial function and cancer; (iii) the interplay between β1 integrins and EGF (epidermal growth factor) receptor; (iv) signal integration connecting integrins and cytokine receptors for interleukins, prolactin and interferons; and (v) how integrins and syndecans co-operate in cell migration.

scholarly journals Germ Granules Functions are Memorized by Transgenerationally Inherited Small RNAs

2019 ◽  
Author(s):  
Itamar Lev ◽  
Itai Antoine Toker ◽  
Yael Mor ◽  
Anat Nitzan ◽  
Guy Weintraub ◽  
...  
Keyword(s):  
Small Rna ◽  
Small Rnas ◽  
Early Embryo ◽  
Small Rna Sequencing ◽  
Wild Type ◽  
P Granules ◽  
Multiple Generations ◽  
C Elegans ◽  
The Core ◽  
Germ Granules

AbstractInC. elegansnematodes, components of liquid-like germ granules were shown to be required for transgenerational small RNA inheritance. Surprisingly, we show here that mutants with defective germ granules (pptr-1,meg-3/4,pgl-1) can nevertheless inherit potent small RNA-based silencing responses, but some of the mutants lose this ability after many generations of homozygosity. Animals mutated inpptr-1, which is required for stabilization of P granules in the early embryo, display extremely strong heritable RNAi responses, which last for tens of generations, long after the responses in wild type animals peter out. The phenotype of mutants defective in the core germ granules proteins MEG-3 and MEG-4, depends on the genotype of the ancestors: Mutants that derive from maternal lineages that had functional MEG-3 and MEG-4 proteins exhibit enhanced RNAi inheritance for multiple generations. While functional ancestralmeg-3/4alleles correct, and even potentiates the ability of mutant descendants to inherit RNAi, defects in germ granules functions can be memorized as well; Wild type descendants that derive from lineages of mutants show impaired RNAi inheritance for many (>16) generations, although their germ granules are intact. Importantly, while P granules are maternally deposited, wild type progeny derived frommeg-3/4male mutants also show reduced RNAi inheritance. Unlike germ granules, small RNAs are inherited also from the sperm. Moreover, we find that the transgenerational effects that depend on the ancestral germ granules require the argonaute protein HRDE-1, which carries heritable small RNAs in the germline. Indeed, small RNA sequencing reveals imbalanced levels of many endogenous small RNAs in germ granules mutants. Strikingly, we find thathrde-1;meg-3/4triple mutants inherit RNAi, althoughhrde-1was previously thought to be essential for heritable silencing. We propose that germ granules sort and shape the RNA pool, and that small RNA inheritance memorizes this activity for multiple generations.

scholarly journals Protein-based condensation mechanisms drive the assembly of RNA-rich P granules

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Helen Schmidt ◽  
Andrea Putnam ◽  
Dominique Rasoloson ◽  
Geraldine Seydoux
Keyword(s):  
Intrinsically Disordered Protein ◽  
P Granules ◽  
C Elegans ◽  
Intrinsically Disordered ◽  
Disordered Protein ◽  
The Core ◽  
C Terminus ◽  
Germ Granules

Germ granules are protein-RNA condensates that segregate with the embryonic germline. In C. elegans embryos, germ (P) granule assembly requires MEG-3, an intrinsically-disordered protein that forms RNA-rich condensates on the surface of PGL condensates at the core of P granules. MEG-3 is related to the GCNA family and contains an N-terminal disordered region (IDR) and a predicted ordered C-terminus featuring an HMG-like motif (HMGL). We find that MEG-3 is modular protein that uses its IDR to bind RNA and its C-terminus to drive condensation. The HMGL motif mediates binding to PGL-3 and is required for co-assembly of MEG-3 and PGL-3 condensates in vivo. Mutations in HMGL cause MEG-3 and PGL-3 to form separate condensates that no longer co-segregate to the germline or recruit RNA. Our findings highlight the importance of protein-based condensation mechanisms and condensate-condensate interactions in the assembly of RNA-rich germ granules.

scholarly journals Proximity labeling identifies LOTUS domain proteins that promote the formation of perinuclear germ granules in C. elegans

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Ian F Price ◽  
Hannah L Hertz ◽  
Benjamin Pastore ◽  
Jillian Wagner ◽  
Wen Tang
Keyword(s):  
Germ Line ◽  
Nuclear Periphery ◽  
P Granules ◽  
C Elegans ◽  
Intrinsically Disordered ◽  
Intrinsically Disordered Regions ◽  
Germ Granules ◽  
Protein Components ◽  
Labeling Method ◽  
Disordered Regions

The germ line produces gametes that transmit genetic and epigenetic information to the next generation. Maintenance of germ cells and development of gametes require germ granules-well-conserved membraneless and RNA-rich organelles. The composition of germ granules is elusive owing to their dynamic nature and their exclusive expression in the germ line. Using C. elegans germ granule, called P granule, as a model system, we employed a proximity-based labeling method in combination with mass spectrometry to comprehensively define its protein components. This set of experiments identified over 200 proteins, many of which contain intrinsically disordered regions. An RNAi-based screen identified factors that are essential for P granule assembly, notably EGGD-1 and EGGD-2, two putative LOTUS-domain proteins. Loss of eggd-1 and eggd-2 results in separation of P granules from the nuclear envelope, germline atrophy and reduced fertility. We show that intrinsically disordered regions of EGGD-1 are required to anchor EGGD-1 to the nuclear periphery while its LOTUS domains are required to promote perinuclear localization of P granules. Together, our work expands the repertoire of P granule constituents and provides new insights into the role of LOTUS-domain proteins in germ granule organization.

scholarly journals The transcriptional corepressor CTBP-1 acts with the SOX family transcription factor EGL-13 to maintain AIA interneuron cell identity in C. elegans

2021 ◽  
Author(s):  
Josh Saul ◽  
Takashi Hirose ◽  
Robert Horvitz
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Cell Fate ◽  
Transcriptional Corepressor ◽  
Cell Identity ◽  
C Elegans ◽  
Dna Binding Specificity ◽  
A Cell ◽  
Transcriptional Corepressors ◽  
And Function

Cell identity is characterized by a distinct combination of gene expression, cell morphology and cellular function established as progenitor cells divide and differentiate. Following establishment, cell identities can be unstable and require active and continuous maintenance throughout the remaining life of a cell. Mechanisms underlying the maintenance of cell identities are incompletely understood. Here we show that the gene ctbp-1, which encodes the transcriptional corepressor C-terminal binding protein-1 (CTBP-1), is essential for the maintenance of the identities of the two AIA interneurons in the nematode Caenorhabditis elegans. ctbp-1 is not required for the establishment of the AIA cell fate but rather functions cell-autonomously and can act in older worms to maintain proper AIA gene expression, morphology and function. From a screen for suppressors of the ctbp-1 mutant phenotype, we identified the gene egl-13, which encodes a SOX family transcription factor. We found that egl-13 regulates AIA function and aspects of AIA gene expression, but not AIA morphology. We conclude that the CTBP-1 protein maintains AIA cell identity in part by utilizing EGL-13 to repress transcriptional activity in the AIAs. More generally, we propose that transcriptional corepressors like CTBP-1 might be critical factors in the maintenance of cell identities, harnessing the DNA-binding specificity of transcription factors like EGL-13 to selectively regulate gene expression in a cell-specific manner.

An isoform of eIF4E is a component of germ granules and is required for spermatogenesis inC. elegans

Development ◽  
2001 ◽  
Vol 128 (20) ◽  
pp. 3899-3912 ◽  
Author(s):  
Anahita Amiri ◽  
Brett D. Keiper ◽  
Ichiro Kawasaki ◽  
Yuan Fan ◽  
Yuji Kohara ◽  
...  
Keyword(s):  
Mrna Levels ◽  
Primary Role ◽  
Control Of Gene Expression ◽  
P Granules ◽  
C Elegans ◽  
Highly Sensitive ◽  
Germ Granules ◽  
Cycle Regulation ◽  
Normal Cell Cycle

Control of gene expression at the translational level is crucial for many developmental processes. The mRNA cap-binding protein, eIF4E, is a key player in regulation of translation initiation; appropriate levels of eIF4E are essential for normal cell-cycle regulation and tissue differentiation. The observation that eIF4E levels are elevated during gametogenesis in several organisms suggests that eIF4E might have a specific role in gamete formation as well. We show that one of the five isoforms of C. elegans eIF4E, IFE-1, is enriched in the germline and is a component of germ granules (P granules). The association of IFE-1 with P granules requires the P-granule protein PGL-1. In vitro PGL-1 interacts directly with IFE-1, but not with the other four isoforms of eIF4E. Analysis of animals depleted of IFE-1 by RNAi shows that IFE-1 is required for spermatogenesis, specifically for efficient progression through the meiotic divisions and for the production of functional sperm, in both hermaphrodites and males. The requirement for IFE-1 is highly sensitive to temperature. IFE-1 is not required for oogenesis, as ife-1(RNAi) hermaphrodites produce viable progeny when normal sperm are supplied. Consistent with a primary role in spermatogenesis, ife-1 mRNA levels are highest in regions of the gonad undergoing spermatogenesis. Our results suggest that C. elegans spermatogenesis requires either this specific isoform of eIF4E or an elevated level of eIF4E.

Segregation of germ granules in living Caenorhabditis elegans embryos: cell-type-specific mechanisms for cytoplasmic localisation

Development ◽  
1996 ◽  
Vol 122 (4) ◽  
pp. 1303-1312 ◽  
Author(s):  
S.N. Hird ◽  
J.E. Paulsen ◽  
S. Strome
Keyword(s):  
Caenorhabditis Elegans ◽  
Laser Scanning ◽  
Daughter Cell ◽  
Laser Scanning Confocal Microscopy ◽  
P Granules ◽  
C Elegans ◽  
Scanning Confocal Microscopy ◽  
Germ Granules ◽  
Cell Type Specific ◽  
P Cells

Germ granules are ribonucleoprotein particles that are thought to function in germline specification in invertebrates and possibly in vertebrates. In Caenorhabditis elegans, these structures, termed P granules, are partitioned to the germline P cells during the early embryonic divisions. By injecting a fluorescently labelled anti-P-granule antibody into the C. elegans germline syncitium, we followed P-granule segregation in live embryos using laser-scanning confocal microscopy. We show that, in early P cells (P0 and P1), P-granule partitioning is achieved primarily by their migration through the cytoplasm towards the site of formation of the germline daughter cell. A different mechanism appears to operate in later P cells (P2 and P3): P granules associate with the nucleus and move with it toward the site of formation of the germline daughter cell, where they are then deposited. At each division, there is also disassembly or degradation of those P granules that remain in the cytoplasm destined for the somatic daughter cell. Microfilaments, microtubules and the product of the gene mes-1 are required for the normal pattern of P-granule segregation in P2.

scholarly journals HLH-2/E2A Expression Links Stochastic and Deterministic Elements of a Cell Fate Decision during C. elegans Gonadogenesis

2019 ◽  
Vol 29 (18) ◽  
pp. 3094-3100.e4 ◽  
Author(s):  
Michelle A. Attner ◽  
Wolfgang Keil ◽  
Justin M. Benavidez ◽  
Iva Greenwald
Keyword(s):  
Cell Fate ◽  
Cell Fate Decision ◽  
C Elegans ◽  
A Cell ◽  
Fate Decision

scholarly journals PGL proteins self associate and bind RNPs to mediate germ granule assembly in C. elegans

2011 ◽  
Vol 192 (6) ◽  
pp. 929-937 ◽  
Author(s):  
Momoyo Hanazawa ◽  
Masafumi Yonetani ◽  
Asako Sugimoto
Keyword(s):  
Mammalian Cells ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Function Analysis ◽  
General Mechanism ◽  
Granule Formation ◽  
C Elegans ◽  
Germ Granules ◽  
Self Association

Germ granules are germ lineage–specific ribonucleoprotein (RNP) complexes, but how they are assembled and specifically segregated to germ lineage cells remains unclear. Here, we show that the PGL proteins PGL-1 and PGL-3 serve as the scaffold for germ granule formation in Caenorhabditis elegans. Using cultured mammalian cells, we found that PGL proteins have the ability to self-associate and recruit RNPs. Depletion of PGL proteins from early C. elegans embryos caused dispersal of other germ granule components in the cytoplasm, suggesting that PGL proteins are essential for the architecture of germ granules. Using a structure–function analysis in vivo, we found that two functional domains of PGL proteins contribute to germ granule assembly: an RGG box for recruiting RNA and RNA-binding proteins and a self-association domain for formation of globular granules. We propose that self-association of scaffold proteins that can bind to RNPs is a general mechanism by which large RNP granules are formed.

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