scholarly journals A new kind of informational suppression in the nematode Caenorhabditis elegans.

Genetics ◽  
1989 ◽  
Vol 123 (2) ◽  
pp. 301-313 ◽  
Author(s):  
J Hodgkin ◽  
A Papp ◽  
R Pulak ◽  
V Ambros ◽  
P Anderson
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
Chain Gene ◽  
Coding Region ◽  
Nematode Caenorhabditis Elegans ◽  
Protein Coding ◽  
Suppressor Mutations ◽  
Allele Specific ◽  
Heterochronic Gene ◽  
Extragenic Suppressors

Abstract Independent reversions of mutations affecting three different Caenorhabditis elegans genes have each yielded representatives of the same set of extragenic suppressors. Mutations at any one of six loci act as allele-specific recessive suppressors of certain allels of unc-54 (a myosin heavy chain gene), lin-29 (a heterochronic gene), and tra-2 (a sex determination gene). The same mutations also suppress certain alleles of another sex determination gene, tra-1, and of a morphogenetic gene, dpy-5. In addition to their suppression phenotype, the suppressor mutations cause abnormal morphogenesis of the male bursa and the hermaphrodite vulva. We name these genes smg-1 through smg-6 (suppressor with morphogenetic effect on genitalia), in order to distinguish them from mab (male abnormal) genes that can mutate to produce abnormal genitalia but which do not act as suppressors (smg-1 and smg-2 are new names for two previously described genes, mab-1 and mab-11). The patterns of suppression, and the interactions between the different smg genes, are described and discussed. In general, suppression is recessive and incomplete, and at least some of the suppressed mutations are hypomorphic in nature. A suppressible allele of unc-54 contains a deletion in the 3' noncoding region of the gene; the protein coding region of the gene is apparently unaffected. This suggests that the smg suppressors affect a process other than translation, for example mRNA processing, transport, or stability.

Major sex-determining genes and the control of sexual dimorphism in Caenorhabditis elegans

Genome ◽  
1989 ◽  
Vol 31 (2) ◽  
pp. 625-637 ◽  
Author(s):  
Jonathan Hodgkin ◽  
Andrew D. Chisholm ◽  
Michael M. Shen
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Germ Line ◽  
Cell Lineage ◽  
Regulatory Genes ◽  
Nematode Caenorhabditis Elegans ◽  
X Chromosomes ◽  
The Many ◽  
Lineage Analysis

Sex determination in Caenorhabditis elegans involves a cascade of major regulatory genes connecting the primary sex determining signal, X chromosome dosage, to key switch genes, which in turn direct development along either male or female pathways. Animals with one X chromosome (XO) are male, while animals with two X chromosomes (XX) are hermaphrodite: hermaphrodite development occurs because the action of the regulatory genes is modified in the germ line so that both sperm and oocytes are made inside a completely female soma. The regulatory genes are being examined by both genetic and molecular means. We discuss how these major genes, in particular the last switch gene in the cascade, tra-1, might regulate the many different sex-specific events that occur during the development of the hermaphrodite and of the male.Key words: nematode, Caenorhabditis elegans, sex determination, sexual differentiation, cell lineage analysis.

scholarly journals Analysis of a lin-42/period Null Allele Implicates All Three Isoforms in Regulation of Caenorhabditis elegans Molting and Developmental Timing

2016 ◽  
Vol 6 (12) ◽  
pp. 4077-4086 ◽  
Author(s):  
Theresa L B Edelman ◽  
Katherine A McCulloch ◽  
Angela Barr ◽  
Christian Frøkjær-Jensen ◽  
Erik M Jorgensen ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Null Allele ◽  
Postembryonic Development ◽  
Developmental Timing ◽  
Critical Element ◽  
Coding Region ◽  
Protein Coding ◽  
Temporal Regulation ◽  
Larval Stages ◽  
Hypomorphic Alleles

Abstract The Caenorhabditis elegans heterochronic gene pathway regulates the relative timing of events during postembryonic development. lin-42, the worm homolog of the circadian clock gene, period, is a critical element of this pathway. lin-42 function has been defined by a set of hypomorphic alleles that cause precocious phenotypes, in which later developmental events, such as the terminal differentiation of hypodermal cells, occur too early. A subset of alleles also reveals a significant role for lin-42 in molting; larval stages are lengthened and ecdysis often fails in these mutant animals. lin-42 is a complex locus, encoding overlapping and nonoverlapping isoforms. Although existing alleles that affect subsets of isoforms have illuminated important and distinct roles for this gene in developmental timing, molting, and the decision to enter the alternative dauer state, it is essential to have a null allele to understand all of the roles of lin-42 and its individual isoforms. To remedy this problem and discover the null phenotype, we engineered an allele that deletes the entire lin-42 protein-coding region. lin-42 null mutants are homozygously viable, but have more severe phenotypes than observed in previously characterized hypomorphic alleles. We also provide additional evidence for this conclusion by using the null allele as a base for reintroducing different isoforms, showing that each isoform can provide heterochronic and molting pathway activities. Transcript levels of the nonoverlapping isoforms appear to be under coordinate temporal regulation, despite being driven by independent promoters. The lin-42 null allele will continue to be an important tool for dissecting the functions of lin-42 in molting and developmental timing.

scholarly journals Distinct and Redundant Functions of μ1 Medium Chains of the AP-1 Clathrin-Associated Protein Complex in the NematodeCaenorhabditis elegans

2000 ◽  
Vol 11 (8) ◽  
pp. 2743-2756 ◽  
Author(s):  
Jaegal Shim ◽  
Paul W. Sternberg ◽  
Junho Lee
Keyword(s):  
Rna Interference ◽  
Caenorhabditis Elegans ◽  
Protein Complex ◽  
Protein Complexes ◽  
Pleiotropic Effects ◽  
Chain Gene ◽  
Hybrid Protein ◽  
Nematode Caenorhabditis Elegans ◽  
Vulval Development ◽  
Redundant Functions

In the nematode Caenorhabditis elegans, there exist two μ1 medium chains of the AP-1 clathrin-associated protein complex. Mutations of unc-101, the gene that encodes one of the μ1 chains, cause pleiotropic effects ( Lee et al., 1994 ). In this report, we identified and analyzed the second μ1 chain gene, apm-1. Unlike the mammalian homologs, the two medium chains are expressed ubiquitously throughout development. RNA interference (RNAi) experiments with apm-1 showed thatapm-1 and unc-101 were redundant in embryogenesis and in vulval development. Consistent with this, a hybrid protein containing APM-1, when overexpressed, rescued the phenotype of an unc-101 mutant. However, single disruptions ofapm-1 or unc-101 have distinct phenotypes, indicating that the two medium chains may have distinct functions. RNAi of any one of the small or large chains of AP-1 complex (ς1, β1, or γ) showed a phenotype identical to that caused by the simultaneous disruption of unc-101 andapm-1, but not that by single disruption of either gene. This suggests that the two medium chains may share large and small chains in the AP-1 complexes. Thus, apm-1 andunc-101 encode two highly related μ1 chains that share redundant and distinct functions within AP-1 clathrin-associated protein complexes of the same tissue.

scholarly journals INDIRECT SUPPRESSION IN CAENORHABDITIS ELEGANS

Genetics ◽  
1978 ◽  
Vol 89 (2) ◽  
pp. 299-314
Author(s):  
Donald L Riddle ◽  
S Brenner
Keyword(s):  
Caenorhabditis Elegans ◽  
Thick Filament ◽  
Suppressor Gene ◽  
Muscle Structure ◽  
Suppressor Mutations ◽  
First Case ◽  
Allele Specific ◽  
Mutant Genes ◽  
Dose Dependent ◽  
Six Genes

ABSTRACT Two cases of indirect suppression have been characterized. One case involves suppressors compensating for defects in muscle structure. Nine independent suppressor mutations were judged to lie in a single suppressor gene, sup-3. Suppression is dominant, but dose dependent, and results in improved locomotion, as well as in an increase in the ability of mutant animals to lay eggs. Mutations in six genes known to affect muscle structure were tested for suppression by representative sup-3 mutations. Alleles of three of the six genes are suppressed, two of which are known to code for thick filament proteins. One suppressor allele was identified as a deletion by genetic criteria. A second case of indirect suppression is not associated with muscle defects, but involves two mutant genes producing uncoordinated phenotypes very similar to one another. As in the first case, suppression is dominant but dose dependent and is not allele specific.

scholarly journals unc-93(e1500): A BEHAVIORAL MUTANT OF CAENORHABDITIS ELEGANS THAT DEFINES A GENE WITH A WILD-TYPE NULL PHENOTYPE

Genetics ◽  
1980 ◽  
Vol 96 (1) ◽  
pp. 147-164 ◽  
Author(s):  
Iva S Greenwald ◽  
H Robert Horvitz
Keyword(s):  
Caenorhabditis Elegans ◽  
Egg Laying ◽  
Null Alleles ◽  
Wild Type ◽  
Nematode Caenorhabditis Elegans ◽  
Genetic Manipulations ◽  
Wild Type Phenotype ◽  
Toxic Product ◽  
Extragenic Suppressors ◽  
Regulatory Functions

ABSTRACT The uncoordinated, egg-laying-defective mutation, unc-93(e1500) III, of the nematode Caenorhabditis elegans spontaneously reverts to a wild-type phenotype. We describe 102 spontaneous and mutagen-induced revertants that define three loci, two extragenic (sup-9 II and sup-10 X) and one intragenic. Genetic analysis suggests that e1500 is a rare visible allele that generates a toxic product and that intragenic reversion, resulting from the generation of null alleles of the unc-93 gene, eliminates the toxic product. We propose that the genetic properties of the unc-93 locus, including the spontaneous reversion of the e1500 mutation, indicate that unc-93 may be a member of a multigene family. The extragenic suppressors also appear to arise as the result of elimination of gene activity; these genes may encode regulatory functions or products that interact with the unc-93 gene product. Genes such as unc-93, sup-9 and sup-10 may be useful for genetic manipulations, including the generation of deficiencies and mutagen testing.

scholarly journals Transposons but Not Retrotransposons Are Located Preferentially in Regions of High Recombination Rate in Caenorhabditis elegans

Genetics ◽  
2000 ◽  
Vol 156 (4) ◽  
pp. 1661-1669 ◽  
Author(s):  
Laurent Duret ◽  
Gabriel Marais ◽  
Christian Biémont
Keyword(s):  
Caenorhabditis Elegans ◽  
Recombination Rate ◽  
Ltr Retrotransposons ◽  
Coding Region ◽  
Nematode Caenorhabditis Elegans ◽  
Noncoding Regions ◽  
Dna And Rna ◽  
Gene Coding ◽  
Intergenic Dna ◽  
The Difference

Abstract We analyzed the distribution of transposable elements (TEs: transposons, LTR retrotransposons, and non-LTR retrotransposons) in the chromosomes of the nematode Caenorhabditis elegans. The density of transposons (DNA-based elements) along the chromosomes was found to be positively correlated with recombination rate, but this relationship was not observed for LTR or non-LTR retrotransposons (RNA-based elements). Gene (coding region) density is higher in regions of low recombination rate. However, the lower TE density in these regions is not due to the counterselection of TE insertions within exons since the same positive correlation between TE density and recombination rate was found in noncoding regions (both in introns and intergenic DNA). These data are not compatible with a global model of selection acting against TE insertions, for which an accumulation of elements in regions of reduced recombination is expected. We also found no evidence for a stronger selection against TE insertions on the X chromosome compared to the autosomes. The difference in distribution of the DNA and RNA-based elements along the chromosomes in relation to recombination rate can be explained by differences in the transposition processes.

scholarly journals fog-2, a germ-line-specific sex determination gene required for hermaphrodite spermatogenesis in Caenorhabditis elegans.

Genetics ◽  
1988 ◽  
Vol 119 (1) ◽  
pp. 43-61 ◽  
Author(s):  
T Schedl ◽  
J Kimble
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
Germ Line ◽  
Negative Regulator ◽  
Loss Of Function ◽  
Wild Type ◽  
Negative Regulators ◽  
Nematode Caenorhabditis Elegans ◽  
Isolation And Characterization

Abstract This paper describes the isolation and characterization of 16 mutations in the germ-line sex determination gene fog-2 (fog for feminization of the germ line). In the nematode Caenorhabditis elegans there are normally two sexes, self-fertilizing hermaphrodites (XX) and males (XO). Wild-type XX animals are hermaphrodite in the germ line (spermatogenesis followed by oogenesis), and female in the soma. fog-2 loss-of-function mutations transform XX animals into females while XO animals are unaffected. Thus, wild-type fog-2 is necessary for spermatogenesis in hermaphrodites but not males. The fem genes and fog-1 are each essential for specification of spermatogenesis in both XX and XO animals. fog-2 acts as a positive regulator of the fem genes and fog-1. The tra-2 and tra-3 genes act as negative regulators of the fem genes and fog-1 to allow oogenesis. Two models are discussed for how fog-2 might positively regulate the fem genes and fog-1 to permit spermatogenesis; fog-2 may act as a negative regulator of tra-2 and tra-3, or fog-2 may act positively on the fem genes and fog-1 rendering them insensitive to the negative action of tra-2 and tra-3.

scholarly journals NOVEL NEMATODE AMBER SUPPRESSORS

Genetics ◽  
1985 ◽  
Vol 111 (2) ◽  
pp. 287-310
Author(s):  
Jonathan Hodgkin
Keyword(s):  
Caenorhabditis Elegans ◽  
Tissue Specificity ◽  
Gene Activity ◽  
The Other ◽  
Nematode Caenorhabditis Elegans ◽  
Maternal Mrna ◽  
Suppressor Mutations ◽  
Amber Suppressor

ABSTRACT Nine amber suppressor mutations were isolated in the nematode Caenorhabditis elegans by reverting amber alleles of a sex-determining gene, tra-3. One suppressor maps to a known locus, sup-5 III, but the other eight map to three new loci, sup-21 X (five alleles), sup-22 IV (two alleles) and sup-23 IV (one allele). Amber alleles of tra-3 and of a dumpy gene, dpy-20, were used to measure the efficiency of suppression; the sup-21 and the sup-22 alleles were both shown to be heterogeneous and generally weaker suppressors than sup-5 alleles, which are homogeneous. The spectrum of mutations suppressed by a strong sup-21 allele, e1957, was investigated and compared to the spectra for the amber suppressors sup-5 III and sup-7 X, using amber alleles in 13 assorted genes. Some of the differences between these spectra may be due to limited tissue specificity in sup-21 expression.—Suppression of dpy-20 was used to show that the sex-linked suppressors sup-7 and sup-21 are not dosage compensated in male (XO) relative to hermaphrodite (XX).—Several uses of amber suppressors are critically discussed: for identifying null mutations, for varying levels of gene activity and for detecting maternal mRNA.

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