scholarly journals AN AUTOSOMAL GENE THAT AFFECTS X CHROMOSOME EXPRESSION AND SEX DETERMINATION IN CAENORHABDITIS ELEGANS

Genetics ◽  
1984 ◽  
Vol 106 (1) ◽  
pp. 29-44
Author(s):  
Philip M Meneely ◽  
William B Wood
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Autosomal Gene ◽  
C Elegans ◽  
Recessive Mutant

ABSTRACT Recessive mutant alleles at the autosomal dpy-21 locus of C. elegans cause a dumpy phenotype in XX animals but not in XO animals. This dumpy phenotype is characteristic of X chromosome aneuploids with higher than normal X to autosome ratios and is proposed to result from overexpression of X-linked genes. We have isolated a new dpy-21 allele that also causes partial hermaphroditization of XO males, without causing the dumpy phenotype. All dpy-21 alleles show hermaphroditization effects in XO males that carry a duplication of part of the X chromosome and also partially suppress a transformer (tra-1) mutation that converts XX animals into males. Experiments with a set of X chromosome duplications show that the defects of dpy-21 mutants can result from interaction with several different regions of the X chromosome. We propose that dpy-21 regulates X chromosome expression and may be involved in interpreting X chromosome dose for the developmental decisions of both sex determination and dosage compensation.

scholarly journals The Caenorhabditis elegans gene sdc-2 controls sex determination and dosage compensation in XX animals.

Genetics ◽  
1989 ◽  
Vol 122 (3) ◽  
pp. 579-593 ◽  
Author(s):  
C Nusbaum ◽  
B J Meyer
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Apparent Effect ◽  
Linked Gene ◽  
Male Development ◽  
Coordinate Control

Abstract We have identified a new X-linked gene, sdc-2, that controls the hermaphrodite (XX) modes of both sex determination and X chromosome dosage compensation in Caenorhabditis elegans. Mutations in sdc-2 cause phenotypes that appear to result from a shift of both the sex determination and dosage compensation processes in XX animals to the XO modes of expression. Twenty-eight independent sdc-2 mutations have no apparent effect in XO animals, but cause two distinct phenotypes in XX animals: masculinization, reflecting a defect in sex determination, and lethality or dumpiness, reflecting a disruption in dosage compensation. The dosage compensation defect can be demonstrated directly by showing that sdc-2 mutations cause elevated levels of several X-linked transcripts in XX but not XO animals. While the masculinization is blocked by mutations in sex determining genes required for male development (her-1 and fem-3), the lethality, dumpiness and overexpression of X-linked genes are not, indicating that the effect of sdc-2 mutations on sex determination and dosage compensation are ultimately implemented by two independent pathways. We propose a model in which sdc-2 is involved in the coordinate control of both sex determination and dosage compensation in XX animals and acts in the regulatory hierarchy at a step prior to the divergence of the two pathways.

Identification of X chromosome regions in Caenorhabditis elegans that contain sex-determination signal elements.

Genetics ◽  
1994 ◽  
Vol 138 (4) ◽  
pp. 1105-1125
Author(s):  
C C Akerib ◽  
B J Meyer
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Dosage Compensation ◽  
X Chromosomes ◽  
Sensitive Region ◽  
Signal Element ◽  
Number Of Genes ◽  
Mutant Phenotypes ◽  
Chromosome Regions

Abstract The primary sex-determination signal of Caenorhabditis elegans is the ratio of X chromosomes to sets of autosomes (X/A ratio). This signal coordinately controls both sex determination and X chromosome dosage compensation. To delineate regions of X that contain counted signal elements, we examined the effect on the X/A ratio of changing the dose of specific regions of X, using duplications in XO animals and deficiencies in XX animals. Based on the mutant phenotypes of genes that are controlled by the signal, we expected that increases (in males) or decreases (in hermaphrodites) in the dose of X chromosome elements could cause sex-specific lethality. We isolated duplications and deficiencies of specific X chromosome regions, using strategies that would permit their recovery regardless of whether they affect the signal. We identified a dose-sensitive region at the left end of X that contains X chromosome signal elements. XX hermaphrodites with only one dose of this region have sex determination and dosage compensation defects, and XO males with two doses are more severely affected and die. The hermaphrodite defects are suppressed by a downstream mutation that forces all animals into the XX mode of sex determination and dosage compensation. The male lethality is suppressed by mutations that force all animals into the XO mode of both processes. We were able to subdivide this region into three smaller regions, each of which contains at least one signal element. We propose that the X chromosome component of the sex-determination signal is the dose of a relatively small number of genes.

scholarly journals The dpy-30 gene encodes an essential component of the Caenorhabditis elegans dosage compensation machinery.

Genetics ◽  
1994 ◽  
Vol 137 (4) ◽  
pp. 999-1018 ◽  
Author(s):  
D R Hsu ◽  
B J Meyer
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Dosage Compensation ◽  
The Other ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Phenotypic Analysis ◽  
General Role ◽  
Essential Component

Abstract The need to regulate X chromosome expression in Caenorhabditis elegans arises as a consequence of the primary sex-determining signal, the X/A ratio (the ratio of X chromosomes to sets of autosomes), which directs 1X@A animals to develop as males and 2X/2A animals to develop as hermaphrodites. C. elegans possesses a dosage compensation mechanism that equalizes X chromosome expression between the two sexes despite their disparity in X chromosome dosage. Previous genetic analysis led to the identification of four autosomal genes, dpy-21, dpy-26, dpy-27 and dpy-28, whose products are essential in XX animals for proper dosage compensation, but not for sex determination. We report the identification and characterization of dpy-30, an essential component of the dosage compensation machinery. Putative null mutations in dpy-30 disrupt dosage compensation and cause a severe maternal-effect, XX-specific lethality. Rare survivors of the dpy-30 lethality are dumpy and express their X-linked genes at higher than wild-type levels. These dpy-30 mutant phenotypes superficially resemble those caused by mutations in dpy-26, dpy-27 and dpy-28; however, detailed phenotypic analysis reveals important differences that distinguish dpy-30 from these genes. In contrast to the XX-specific lethality caused by mutations in the other dpy genes, the XX-specific lethality caused by dpy-30 mutations is completely penetrant and temperature sensitive. In addition, unlike the other genes, dpy-30 is required for the normal development of XO animals. Although dpy-30 mutations do not significantly affect the viability of XO animals, they do cause them to be developmentally delayed and to possess numerous morphological and behavioral abnormalities. Finally, dpy-30 mutations can dramatically influence the choice of sexual fate in animals with an ambiguous sexual identity, despite having no apparent effect on the sexual phenotype of otherwise wild-type animals. Paradoxically, depending on the genetic background, dpy-30 mutations cause either masculinization or feminization, thus revealing the complex regulatory relationship between the sex determination and dosage compensation processes. The novel phenotypes caused by dpy-30 mutations suggest that in addition to acting in the dosage compensation process, dpy-30 may play a more general role in the development of both XX and XO animals.

scholarly journals X chromosome duplications affect a region of the chromosome they do not duplicate in Caenorhabditis elegans.

Genetics ◽  
1988 ◽  
Vol 119 (2) ◽  
pp. 365-375
Author(s):  
P M Meneely ◽  
K D Nordstrom
Keyword(s):  
Gene Expression ◽  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Linked Gene ◽  
Hypomorphic Mutation ◽  
Level Of Activity

Abstract X chromosome duplications have been used previously to vary the dose of specific regions of the X chromosome to study dosage compensation and sex determination in Caenorhabditis elegans. We show here that duplications suppress and X-linked hypomorphic mutation and elevate the level of activity of an X-linked enzyme, although these two genes are located in a region of the X chromosome that is not duplicated. The effects do not depend on the region of the X chromosome duplicated and is stronger in strains with two doses of a duplication than in strains with one dose. This is evidence for a general elevation of X-linked gene expression in strains carrying X-chromosome duplications, consistent with the hypothesis that the duplications titrate a repressor acting on many X-linked genes.

scholarly journals The role of sdc-1 in the sex determination and dosage compensation decisions in Caenorhabditis elegans.

Genetics ◽  
1990 ◽  
Vol 124 (1) ◽  
pp. 91-114 ◽  
Author(s):  
A M Villeneuve ◽  
B J Meyer
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
Dosage Compensation ◽  
Temperature Shift ◽  
Linked Gene ◽  
C Elegans ◽  
Genetic Mosaic ◽  
Morphological Defects ◽  
Gene Transcripts ◽  
The One

Abstract Our previous work demonstrated that mutations in the X-linked gene sdc-1 disrupt both sex determination and dosage compensation in Caenorhabditis elegans XX animals, suggesting that sdc-1 acts at a step that is shared by the sex determination and dosage compensation pathways prior to their divergence. In this report, we extend our understanding of early events in C. elegans sex determination and dosage compensation and the role played by sdc-1 in these processes. First, our analysis of 14 new sdc-1 alleles suggests that the phenotypes resulting from the lack of sdc-1 function are (1) an incompletely penetrant sexual transformation of XX animals toward the male fate, and (2) increased levels of X-linked gene transcripts in XX animals, correlated with XX-specific morphological defects but not significant XX-specific lethality. Further, all alleles exhibit strong maternal rescue for all phenotypes assayed. Second, temperature-shift experiments suggest that sdc-1 acts during the first half of embryogenesis in determining somatic sexual phenotype, long before sexual differentiation actually takes place, and consistent with our previous proposal that sdc-1 acts at an early step in the regulatory hierarchy controlling the choice of sexual fate. Other temperature-shift experiments suggest that sdc-1 may be involved in establishing but not maintaining the XX mode of dosage compensation. Third, a genetic mosaic analysis of sdc-1 produced an unusual result: the genotypic mosaics failed to display the sdc-1 sexual transformation phenotypes. This result suggests several possible interpretations: (1) sdc-1 is expressed immediately, in the one- or two-celled embryo; (2) sdc-1 acts non-cell-autonomously, such that expression of the gene in either the AB or P1 lineage can supply sdc-1(+) function to cells of the other lineage; (3) the X/A ratio is assessed immediately, in the one- or two-celled embryo; or (4) the X/A signal directs the choice of sexual fate in a non-cell-autonomous fashion. Finally, examination of the classes of sexual phenotypes produced in sdc-1 mutant strains suggests that different cells in the organism may not choose their sexual fates independently.

scholarly journals POLYPLOIDS AND SEX DETERMINATION IN CAENORHABDITIS ELEGANS

Genetics ◽  
1979 ◽  
Vol 93 (2) ◽  
pp. 393-402 ◽  
Author(s):  
James E Madl ◽  
Robert K Herman
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Constitution ◽  
Diploid Males ◽  
C Elegans

ABSTRACT Tetraploid stocks of Caenorhabditis elegans var. Bristol carrying autosomal and X-linked markers have been produced. Tetraploid hermaphrodites fall into two categories: those that give about 1% male self-progeny and those that give 25 to 40% male self-progeny, The former are basically 4A;4X—four sets of autosomes and four sex chromosomes—and the latter are 4A;3X. Males are 4A;2X. (Diploid hermaphrodites are 2A;2X; males are 2A;IX.) Triploids wsre produced by crossing tetraploid hermaphrodites and diploid males. Triploids of composition 3A;3X are hermaphrodites; 3A;2X animals are fertile males. Different X-chromosome duplications were added to a 3A;2X chromosome constitution to increase the X-to-autosome ratio. Based on the resulting sexual phenotypes, we conclude that there exists on the C. elegans X chromosome at least three (and perhaps many mare) dose-sensitive sites that act cumulatively in determining sex.

scholarly journals Sex determination in polyploids of Caenorhabditis elegans.

Genetics ◽  
1994 ◽  
Vol 137 (2) ◽  
pp. 467-481
Author(s):  
P M Meneely
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Dna Sequences ◽  
Maternal Effect ◽  
Indirect Evidence ◽  
Sex Reversal ◽  
Diploid Males ◽  
X Chromosomes

Abstract In Caenorhabditis elegans triploid animals with two X chromosomes (symbolized 3A;2X) are males. However, these triploid males can be feminized by making them mutant for recessive dosage compensation mutations, by adding X chromosome duplications or by microinjecting particular DNA sequences termed feminizing elements. None of these treatments affects diploid males. This study explores several aspects of these treatments in polyploids. The dosage compensation mutants exhibit a strong maternal effect, such that reduction of any of the dosage compensation gene functions in the mother leads to sex reversal of 3A;2X animals. Likewise, all X chromosome duplications tested cause both sex reversal and intersexual development of many 3A;2X animals. Microinjected feminizing element DNA does not cause extensive sex reversal, but does result in intersexual development in 3A;2X animals. Neither X chromosome duplications nor microinjected feminizing elements show that extreme maternal effect of the dosage compensation mutants, although there is indirect evidence for a maternal effect of the feminizing elements. In particular, very little feminizing element DNA needs to be microinjected in order to feminize triploid males, far less than what is needed for stable inheritance, implying that feminizing elements can work within the mother's gonad. However, even very high concentrations of microinjected feminizing elements do not affect sex determination in diploid males, suggesting that they are not part of the numerator of the X/A ratio. In addition, no pair of X chromosome duplications feminizes diploid males, suggesting that none of these duplications contains a numerator of the X/A ratio. Instead, I infer that an X-linked locus, as yet undefined, must be present in two copies for hermaphrodite development to ensue or that the two X chromosomes might interact.

xol-1: A gene that controls the male modes of both sex determination and X chromosome dosage compensation in C. elegans

Cell ◽  
1988 ◽  
Vol 55 (1) ◽  
pp. 167-183 ◽  
Author(s):  
Leilani M. Miller ◽  
John D. Plenefisch ◽  
Lawrence P. Casson ◽  
Barbara J. Meyer
Keyword(s):  
Sex Determination ◽  
X Chromosome ◽  
Dosage Compensation ◽  
C Elegans

scholarly journals Chromosome-wide evolution and sex determination in a nematode with three sexes

2018 ◽  
Author(s):  
Sophie Tandonnet ◽  
Georgios D. Koutsovoulos ◽  
Sally Adams ◽  
Delphine Cloarec ◽  
Manish Parihar ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Environmental Factors ◽  
Sex Determination ◽  
Differential Expression ◽  
Candidate Genes ◽  
X Chromosome ◽  
Linkage Groups ◽  
Free Living ◽  
C Elegans ◽  
Free Living Nematode

AbstractThe free-living nematode Auanema rhodensis is a rare example of a species with three sexes, in which males, females and hermaphrodites coexist. A. rhodensis males have only one X chromosome (XO), whereas females and hermaphrodites have two (XX). The A. rhodensis X chromosome is unusual: it does not recombine in hermaphrodites and is transmitted from father to son. The mechanism that controls the production of females versus hermaphrodites is unknown but is dependent on maternal and larval environmental factors. Here we report the genome sequence and genetic map of A. rhodensis, placing over 95% of the sequence in seven linkage groups. Comparison of the seven A. rhodensis chromosomes to chromosomal assemblies of Caenorhabditis elegans and three other rhabditine nematodes identified deeply conserved linkage groups we call Nigon units, some of which have been maintained in all species analysed. Others have undergone breakage and fusion, and the A. rhodensis karyotype is the product of a unique set of rearrangements involving three Nigon units. The A. rhodensis X chromosome is much smaller than the autosomes, is less gene dense and is 3 to 4 times more polymorphic, reflecting its unique transmission history. Differential expression analyses comparing females and hermaphrodites, identified several candidate genes, including orthologues of C. elegans gld-1, tra-1 and dmd-10/11, that are potentially involved in the female-hermaphrodite sexual decision.

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