Distinct Requirements for Somatic and Germline Expression of a Generally Expressed Caernorhabditis elegans Gene

In screening for embryonic-lethal mutations in Caernorhabditis elegans, we defined an essential gene (let-858) that encodes a nuclear protein rich in acidic and basic residues. We have named this product nucampholin. Closely homologous sequences in yeast, plants, and mammals demonstrate strong evolutionary conservation in eukaryotes. Nucampholin resides in all nuclei of C. elegans and is essential in early development and in differentiating tissue. Antisense-mediated depletion of LET-858 activity in early embryos causes a lethal phenotype similar to characterized treatments blocking embryonic gene expression. Using transgene-rescue, we demonstrated the additional requirement for let-858 in the larval germline. The broad requirements allowed investigation of soma-germline differences in gene expression. When introduced into standard transgene arrays, let-858 (like many other C. elegans genes) functions well in soma but poorly in germline. We observed incremental silencing of simple let-858 arrays in thefirstfew generations following transformation and hypothesized that silencing might reflect recognition of arrays as repetitive or heterochromatin-like. To give the transgene a more physiological context, we included an excess of random genomic fragments with the injected DNA. The resulting transgenes show robust expression in both germline and soma. Our results suggest the possibility of concerted mechanisms for silencing unwanted germline expression of repetitive sequences.

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Maternal-effect lethal mutations on linkage group II of Caenorhabditis elegans.

Genetics ◽

10.1093/genetics/120.4.977 ◽

1988 ◽

Vol 120 (4) ◽

pp. 977-986

Author(s):

K J Kemphues ◽

M Kusch ◽

N Wolf

Keyword(s):

Caenorhabditis Elegans ◽

Linkage Group ◽

Maternal Effect ◽

Essential Genes ◽

The Other ◽

C Elegans ◽

Lethal Mutations ◽

Embryonic Lethal ◽

Embryonic Lethal Mutations ◽

F1 Progeny

Abstract We have analyzed a set of linkage group (LG) II maternal-effect lethal mutations in Caenorhabditis elegans isolated by a new screening procedure. Screens of 12,455 F1 progeny from mutagenized adults resulted in the recovery of 54 maternal-effect lethal mutations identifying 29 genes. Of the 54 mutations, 39 are strict maternal-effect mutations defining 17 genes. These 17 genes fall into two classes distinguished by frequency of mutation to strict maternal-effect lethality. The smaller class, comprised of four genes, mutated to strict maternal-effect lethality at a frequency close to 5 X 10(-4), a rate typical of essential genes in C. elegans. Two of these genes are expressed during oogenesis and required exclusively for embryogenesis (pure maternal genes), one appears to be required specifically for meiosis, and the fourth has a more complex pattern of expression. The other 13 genes were represented by only one or two strict maternal alleles each. Two of these are identical genes previously identified by nonmaternal embryonic lethal mutations. We interpret our results to mean that although many C. elegans genes can mutate to strict maternal-effect lethality, most genes mutate to that phenotype rarely. Pure maternal genes, however, are among a smaller class of genes that mutate to maternal-effect lethality at typical rates. If our interpretation is correct, we are near saturation for pure maternal genes in the region of LG II balanced by mnC1. We conclude that the number of pure maternal genes in C. elegans is small, being probably not much higher than 12.

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A Survey of New Temperature-Sensitive, Embryonic-Lethal Mutations in C. elegans: 24 Alleles of Thirteen Genes

PLoS ONE ◽

10.1371/journal.pone.0016644 ◽

2011 ◽

Vol 6 (3) ◽

pp. e16644 ◽

Cited By ~ 40

Author(s):

Sean M. O'Rourke ◽

Clayton Carter ◽

Luke Carter ◽

Sara N. Christensen ◽

Minh P. Jones ◽

...

Keyword(s):

Temperature Sensitive ◽

C Elegans ◽

Lethal Mutations ◽

Embryonic Lethal ◽

Embryonic Lethal Mutations

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A Limited Number of Caenorhabditis elegans Genes Are Readily Mutable to Dominant, Temperature-Sensitive Maternal-Effect Embryonic Lethality

Genetics ◽

10.1093/genetics/147.4.1665 ◽

1997 ◽

Vol 147 (4) ◽

pp. 1665-1674 ◽

Cited By ~ 3

Author(s):

Nancy L Mitenko ◽

James R Eisner ◽

John R Swiston ◽

Paul E Mains

Keyword(s):

Caenorhabditis Elegans ◽

Maternal Effect ◽

Temperature Sensitive ◽

Loss Of Function ◽

Gain Of Function ◽

C Elegans ◽

Lethal Mutations ◽

Embryonic Lethal ◽

Embryonic Lethal Mutations ◽

Dominant Temperature Sensitive

Abstract Dominant gain-of-function mutations can give unique insights into the study of gene function. In addition, gain-of-function mutations, unlike loss-of-function alleles, are not biased against the identification of genetically redundant loci. To identify novel genetic functions active during Caenorhabditis elegans embryogenesis, we have collected a set of dominant temperature-sensitive maternal-effect embryonic lethal mutations. In a previous screen, we isolated eight such mutations, distributed among six genes. In the present study, we describe eight new dominant mutations that identify only three additional genes, yielding a total of 16 dominant mutations found in nine genes. Therefore, it appears that a limited number of C. elegans genes mutate to this phenotype at appreciable frequencies. Five of the genes that we identified by dominant mutations have loss-of-function alleles. Two of these genes may lack loss-of-function phenotypes, indicating that they are nonessential and so may represent redundant loci. Loss-of-function mutations of three other genes are associated with recessive lethality, indicating nonredundancy.

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Nematode Small RNA Pathways in the Absence of piRNAs

10.1101/2021.07.23.453445 ◽

2021 ◽

Author(s):

Maxim Zagoskin ◽

Jianbin Wang ◽

Ashley T. Neff ◽

Giovana M.B. Veronezi ◽

Richard E. Davis

Keyword(s):

Small Rna ◽

Small Rnas ◽

Parasitic Nematode ◽

Repetitive Sequences ◽

C Elegans ◽

Early Embryos ◽

Specific Mrnas ◽

Rna Pathways ◽

Pirna Pathway ◽

Mature Mrnas

Small RNA pathways play diverse regulatory roles in the nematode C. elegans. However, our understanding of small RNA pathways, their conservation, and their roles in other nematodes is limited. Here, we analyzed small RNA pathways in the parasitic nematode Ascaris. Ascaris has ten Argonautes with five worm-specific Argonautes (WAGOs) that are associated with secondary 5'-triphosphate small RNAs (22-24G-RNAs). These Ascaris WAGOs and their small RNAs target repetitive sequences (WAGO-1, WAGO-2, WAGO-3, and NRDE-3) or mature mRNAs (CSR-1, NRDE-3, and WAGO-3) and are similar to the C. elegans mutator, nuclear, and CSR-1 small RNA pathways. Ascaris CSR-1 likely functions to "license" gene expression in the absence of an Ascaris piRNA pathway. Ascaris ALG-4 and its associated 26G-RNAs target and appear to repress specific mRNAs during meiosis in the testes. Notably, Ascaris WAGOs (WAGO-3 and NRDE-3) small RNAs change their targets between repetitive sequences and mRNAs during spermatogenesis or in early embryos illustrating target plasticity of these WAGOs. We provide a unique and comprehensive view of mRNA and small RNA expression throughout nematode spermatogenesis that illustrates the dynamics and flexibility of small RNA pathways. Overall, our study provides key insights into the conservation and divergence of nematode small RNA pathways.

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Faculty Opinions recommendation of Automated analysis of embryonic gene expression with cellular resolution in C. elegans.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1119583.575800 ◽

2008 ◽

Author(s):

Morris Maduro

Keyword(s):

Gene Expression ◽

Automated Analysis ◽

C Elegans ◽

Cellular Resolution

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Faculty Opinions recommendation of Glucose shortens the life span of C. elegans by downregulating DAF-16/FOXO activity and aquaporin gene expression.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1279994.747101 ◽

2009 ◽

Author(s):

Thomas Baranski ◽

Laura Palanker Musselman

Keyword(s):

Gene Expression ◽

Life Span ◽

C Elegans ◽

Aquaporin Gene

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Faculty Opinions recommendation of Argonautes promote male fertility and provide a paternal memory of germline gene expression in C. elegans.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.718215517.793490580 ◽

2014 ◽

Author(s):

Peter Boag ◽

Pauline Cottee

Keyword(s):

Gene Expression ◽

Male Fertility ◽

Germline Gene ◽

C Elegans

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The secreted endoribonuclease ENDU-2 from the soma protects germline immortality in C. elegans

Nature Communications ◽

10.1038/s41467-021-21516-6 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Wenjing Qi ◽

Erika D. V. Gromoff ◽

Fan Xu ◽

Qian Zhao ◽

Wei Yang ◽

...

Keyword(s):

Gene Expression ◽

Stem Cell ◽

Small Rnas ◽

C Elegans ◽

Cleavage Activity ◽

Response To Temperature ◽

Multicellular Organisms ◽

Cell Immortality ◽

Mature Mrnas ◽

Endoribonuclease Activity

AbstractMulticellular organisms coordinate tissue specific responses to environmental information via both cell-autonomous and non-autonomous mechanisms. In addition to secreted ligands, recent reports implicated release of small RNAs in regulating gene expression across tissue boundaries. Here, we show that the conserved poly-U specific endoribonuclease ENDU-2 in C. elegans is secreted from the soma and taken-up by the germline to ensure germline immortality at elevated temperature. ENDU-2 binds to mature mRNAs and negatively regulates mRNA abundance both in the soma and the germline. While ENDU-2 promotes RNA decay in the soma directly via its endoribonuclease activity, ENDU-2 prevents misexpression of soma-specific genes in the germline and preserves germline immortality independent of its RNA-cleavage activity. In summary, our results suggest that the secreted RNase ENDU-2 regulates gene expression across tissue boundaries in response to temperature alterations and contributes to maintenance of stem cell immortality, probably via retaining a stem cell specific program of gene expression.

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