Embryonic Development in Caenorhabditis elegans

56 nerve cells are added to the ventral cord and associated ganglia of Caenorhabditis elegans at about the time of the first larval moult. These cells are produced by the uniform division of 13 neuroblasts followed by a defined pattern of cell deaths. Comparison with the data in the previous paper suggests that there is a relationship between the ancestry of a cell and its function. The significance of programmed cell death is discussed.

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Overlapping and non-overlapping roles of the class-I histone deacetylase-1 corepressors, LET-418, SIN-3, and SPR-1 in Caenorhabditis elegans embryonic development

10.1101/2020.07.21.213561 ◽

2020 ◽

Author(s):

Yukihiro Kubota ◽

Yuto Ohnishi ◽

Tasuku Hamasaki ◽

Gen Yasui ◽

Natsumi Ota ◽

...

Keyword(s):

Caenorhabditis Elegans ◽

Embryonic Development ◽

Histone Deacetylases ◽

Class I ◽

Biological Processes ◽

Nucleosome Remodeling ◽

C Elegans ◽

Histone Deacetylase 1 ◽

Genome Wide ◽

Sin3 Complex

AbstractHistone deacetylases (HDACs) are divided into four classes. Class-I HDAC, HDAC-1 forms three types of complexes, namely the Nucleosome Remodeling Deacetylase complex, the Sin3 complex, and the CoREST complex, with specific corepressor component Mi2/CHD-3, Sin3, and RCOR1 in human, respectively. The functions of these HDAC-1 complexes are regulated by their corepressors, however, their exact mechanistic roles in several biological processes remain unexplored, such as in embryonic development. Here, we report that each of the corepressors, LET-418, SIN-3, and SPR-1, the homologous of Mi2, Sin3, and RCOR1, respectively, were expressed throughout Caenorhabditis elegans embryonic development and served essential roles in the process. Moreover, genetic analysis suggested that three pathways (i.e., LET-418– SIN-3–SPR-1, SIN-3–SPR-1, and LET-418) participated in embryonic development. Our terminal-phenotype observations of single mutants of each corepressor implied that LET-418, SIN-3, and SPR-1 played similar roles in promoting advancement to the middle and late embryonic stages. Genome-wide comparative-transcriptome analysis indicated that 47.5% and 42.3% of genes were commonly increased and decreased in sin-3 and spr-1 mutants, respectively. These results suggest that among the three pathways studied, the SIN-3–SPR-1 pathway mainly serves to regulate embryonic development. Comparative-Gene Ontology analysis indicated that these three pathways played overlapping and distinct roles in regulating C. elegans embryonic development.

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Translation and codon usage regulate Argonaute slicer activity to trigger small RNA biogenesis

10.1101/2020.09.04.282863 ◽

2020 ◽

Author(s):

Meetali Singh ◽

Eric Cornes ◽

Blaise Li ◽

Piergiuseppe Quarato ◽

Loan Bourdon ◽

...

Keyword(s):

Caenorhabditis Elegans ◽

Embryonic Development ◽

Rna Polymerase ◽

Codon Usage ◽

Small Rna ◽

Small Rnas ◽

Rna Dependent Rna Polymerase ◽

Coding Sequences ◽

Germ Granules ◽

Rna Biogenesis

In the Caenorhabditis elegans germline, thousands of mRNAs are concomitantly expressed with antisense 22G-RNAs, which are loaded into the Argonaute CSR-1. Despite their essential functions for animal fertility and embryonic development, how CSR-1 22G-RNAs are produced remains unknown. Here, we show that CSR-1 slicer activity is primarily involved in triggering the synthesis of small RNAs on the coding sequences of germline mRNAs and post-transcriptionally regulates a fraction of targets. CSR-1-cleaved mRNAs prime the RNA-dependent RNA polymerase, EGO-1, to synthesize 22G-RNAs in phase with ribosome translation in the cytoplasm, in contrast to other 22G-RNAs mostly synthesized in germ granules. Moreover, codon optimality and efficient translation antagonize CSR-1 slicing and 22G-RNAs biogenesis. We propose that codon usage differences encoded into mRNA sequences might be a conserved strategy in eukaryotes to regulate small RNA biogenesis and Argonaute targeting.

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Introduction

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2003.1335 ◽

2003 ◽

Vol 358 (1436) ◽

pp. 1313-1315 ◽

Cited By ~ 4

Author(s):

R. L. Gardner ◽

M. A. Surani ◽

D. Solter

Keyword(s):

Caenorhabditis Elegans ◽

Embryonic Development ◽

Marine Invertebrates ◽

De Novo ◽

Cellular Growth ◽

Cellular Interactions ◽

Complex Organization ◽

Careful Documentation ◽

Fertilized Egg ◽

Extreme View

The elaboration of a physiologically integrated organism from a fertilized egg depends on processes of cellular growth and diversification that require very precise coordination in both space and time. The extent to which the final outcome is presaged in the egg is an issue that has engaged those seeking to explain embryonic development since antiquity. According to the concept of preformation espoused by Charles Bonnet, the new organism was already present in its final form in the egg, so that development simply entailed enlargement without any accompanying increase in complexity (Oppenheimer 1967). This extreme view was shown to be untenable by Caspar Friedrich Wolff, whose relevant studies included careful documentation of the emergence of increasingly complex organization during the course of embryogenesis in the chick. As a result, the opposing concept of epigenesis, namely that order and form emerge de novo during the course of development, rapidly gained dominance (Oppenheimer 1967). However, by the latter half of the nineteenth century, preformation was revived in a subtler guise to explain the development of various marine invertebrates in which both patterns of cleavage and differentiation of the resulting blastomeres were essentially invariant. Here, cellular diversification was attributed to the localization within the cytoplasm of the egg of factors, or ‘determinants’, which dictated the fate of the cells that inherited them. The stereotypical pattern of cleavage exhibited by such organisms was referred to as ‘mosaic’, in contrast to the variable or ‘regulative’ pattern shown by many others. Mosaic soon came to be equated with a determinant–based or neo–preformationist, and regulative with an epigenetic, view of development. We now know that this distinction is not valid because cellular interactions play a vital part in the development even of organisms with invariant lineage like Caenorhabditis elegans, whereas ‘determinants’ such as those for the germline occur in species whose lineage is variable.

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The C. elegans septin genes, unc-59 and unc-61, are required for normal postembryonic cytokineses and morphogenesis but have no essential function in embryogenesis

Journal of Cell Science ◽

10.1242/jcs.113.21.3825 ◽

2000 ◽

Vol 113 (21) ◽

pp. 3825-3837 ◽

Cited By ~ 4

Author(s):

T.Q. Nguyen ◽

H. Sawa ◽

H. Okano ◽

J.G. White

Keyword(s):

Caenorhabditis Elegans ◽

Embryonic Development ◽

Sensory Neurons ◽

Leading Edge ◽

The Other ◽

Male Tail ◽

Genomic Database ◽

C Elegans ◽

Essential Function ◽

Normal Embryonic Development

Septins have been shown to play important roles in cytokinesis in diverse organisms ranging from yeast to mammals. In this study, we show that both the unc-59 and unc-61 loci encode Caenorhabditis elegans septins. Genomic database searches indicate that unc-59 and unc-61 are probably the only septin genes in the C. elegans genome. UNC-59 and UNC-61 localize to the leading edge of cleavage furrows and eventually reside at the midbody. Analysis of unc-59 and unc-61 mutants revealed that each septin requires the presence of the other for localization to the cytokinetic furrow. Surprisingly, unc-59 and unc-61 mutants generally have normal embryonic development; however, defects were observed in post-embryonic development affecting the morphogenesis of the vulva, male tail, gonad, and sensory neurons. These defects can be at least partially attributed to failures in post-embryonic cytokineses although our data also suggest other possible roles for septins. unc-59 and unc-61 double mutants show similar defects to each of the single mutants.

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