Segregation of developmental potential in early embryos of caenorhabditis elegans

Laufer, John S.; Bazzicalupo, Paolo; Wood, William B.

doi:10.1016/s0092-8674(80)80033-x

Cited by 213 publications

(107 citation statements)

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“…All assays in this study were performed ''blind''; i.e., the person manipulating the embryos and/or scoring the differentiation marker did not know the strain identity; experiments were repeated at least five times for each genotype, as described in the legends for Figures 3 and 4: i. The most convenient (and foolproof) assay for gut differentiation is birefringent gut granules (Chitwood and Chitwood 1974;Laufer et al 1980), which can first be detected when the embryonic intestine has approximately eight cells and which depend on zygotic transcription soon after endoderm specification (Edgar and McGhee 1988). To eliminate the possibility of selective loss of any particular class of embryos during manipulation, gravid hermaphrodites were placed on NGM-agar pads poured directly onto microscope slides and lightly seeded with bacterial food; after 7 6 2 hr of egg laying, adults were removed and the slide incubated at 20°to allow viable embryos to hatch.…”

Section: Background and Expected Resultsmentioning

confidence: 99%

Reevaluation of the Role of the med-1 and med-2 Genes in Specifying the Caenorhabditis elegans Endoderm

Goszczynski

McGhee

2005

Genetics

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The med-1 and med-2 genes encode a pair of essentially identical GATA factor-related transcription factors that have been proposed to be necessary for specification of the C. elegans endoderm (intestine or E lineage) as well as part of the C. elegans mesoderm. med-1 and med-2 are proposed to be the direct downstream targets and the principal effectors of the maternally provided SKN-1 transcription factor; med-1 and med-2 would thus occupy the pivotal interface between maternal and zygotic control of gene expression. The conclusion that med-1 and med-2 are necessary for C. elegans endoderm specification was based on a partially penetrant (50%) loss of endoderm markers produced by RNA-mediated interference (RNAi). To determine whether this partial penetrance reflects: (i) inefficient RNAi against early zygotic transcripts, (ii) experimental uncertainty in the expected level of endoderm loss in skn-1 nulls, or (iii) additional redundancy in the pathway of endoderm specification, we constructed worm strains that segregate embryos lacking both the med-1 gene (because of a gene-specific deletion) and the med-2 gene (using either of two chromosomal deficiencies). Contrary to expectations, we observe that only 3-20% of med-2(ÿ); med-1(ÿ) embryos do not express markers of endoderm differentiation. Furthermore, we found no evidence for a maternal contribution of the med genes to endoderm specification. We conclude that the major pathway(s) for endoderm specification in C. elegans must be independent of the med-1 and med-2 genes. T HE Caenorhabditis elegans endoderm (intestine or E lineage) is clonally derived from a single cell, the E cell, in the eight-cell embryo (Sulston et al. 1983). The early endoderm is one of the few C. elegans lineages for which a plausible specification pathway has been proposed in molecular detail, beginning with maternally provided transcription factors, progressing through several waves of zygotically produced transcription factors, and ending with gene products that function in the terminally differentiated intestine (see review by Maduro and Rothman 2002; see also Baugh et al. 2003Baugh et al. , 2005Robertson et al. 2004). Figure 1 summarizes the regulatory cascade proposed for specification of the C. elegans endoderm. The maternally provided b-ZIP-like transcription factor SKN-1 is essential for correct specification of the fate of the EMS blastomere of the four-cell embryo (Bowerman et al. 1992(Bowerman et al. , 1993. Within the EMS cell, SKN-1 is proposed to directly activate the zygotic expression of two genes called med-1 and med-2, which encode zinc-finger proteins related to GATA-type transcription factors but with atypical binding sites (Maduro et al. 2001;Maduro and Rothman 2002;Broitman-Maduro et al. 2005).These two small intronless genes are 98% identical and, for convenience, are often referred to simply as the med genes (mesendoderm-determining); they are the principal subjects of this article. The med genes are proposed to specify both the C. elegans endoderm and that p...

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Section: Background and Expected Resultsmentioning

confidence: 99%

Reevaluation of the Role of the med-1 and med-2 Genes in Specifying the Caenorhabditis elegans Endoderm

Goszczynski

McGhee

2005

Genetics

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“…To further characterize the arrest phenotype, mounted embryos were incubated overnight at 15°C and terminal phenotypes analyzed. By far the most common phenotype (33.8%) consisted of a mass of Ͻ100 undifferentiated cells (Figure 4, H and I), with no evidence for rhabditin granules (a marker for gut differentiation; Babu, 1974;Laufer et al, 1980). This phenotype was investigated more fully, as described below.…”

Section: Molecular Biology Of the Cell 1332mentioning

confidence: 99%

Regulated Disruption of Inositol 1,4,5-Trisphosphate Signaling inCaenorhabditis elegansReveals New Functions in Feeding and Embryogenesis

Walker

Gower

et al. 2002

MBoC

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Inositol 1,4,5-trisphosphate (IP 3 ) is an important second messenger in animal cells and is central to a wide range of cellular responses. The major intracellular activity of IP 3 is to regulate release of Ca 2ϩ from intracellular stores through IP 3 receptors (IP 3 Rs). We describe a system for the transient disruption of IP 3 signaling in the model organism Caenorhabditis elegans. The IP 3 binding domain of the C. elegans IP 3 R, ITR-1, was expressed from heat shock-induced promoters in live animals. This results in a dominant-negative effect caused by the overexpressed IP 3 binding domain acting as an IP 3 "sponge." Disruption of IP 3 signaling resulted in disrupted defecation, a phenotype predicted by previous genetic studies. This approach also identified two new IP 3 -mediated processes. First, the up-regulation of pharyngeal pumping in response to food is dependent on IP 3 signaling. RNA-mediated interference studies and analysis of itr-1 mutants show that this process is also IP 3 R dependent. Second, the tissue-specific expression of the dominant-negative construct enabled us to circumvent the sterility associated with loss of IP 3 signaling through the IP 3 R and thus determine that IP 3 -mediated signaling is required for multiple steps in embryogenesis, including cytokinesis and gastrulation. Inositol 1,4, ) is an important and widely used second messenger in animal cells. IP 3 is produced by the hydrolysis of phosphatidylinositol 4,5-bisphosphate after the activation of phospholipase C (PLC). The best understood routes of PLC activation are through the stimulation of G protein-coupled receptors or tyrosine kinase-linked receptors at the cell surface, although the presence of additional isoforms of PLC suggests other possible routes (Rhee and Bae, 1997;Katan, 1998). The only known action of IP 3 is to induce Ca 2ϩ release from intracellular stores through activation of IP 3 receptors (IP 3 Rs) (Berridge, 1993). This pathway and the Ca 2ϩ signals derived from it are central to a wide range of cellular responses (Berridge, 1993(Berridge, , 1997Clapham 1995). INTRODUCTIONTwo challenges in the study of this signaling network are to unravel the different functions played by IP 3 signaling in animals and to develop methods for manipulating these processes and thus advance our understanding of how the specificity of IP 3 signaling is achieved. Recent genetic approaches have provided new insights into IP 3 function in animals. The central role played by IP 3 Rs in a wide range of cellular responses is reflected by the high level of lethality resulting from gene knockout observed in both Drosophila (Acharya et al., 1997;Venkatesh and Hasan, 1997) and mice (Matsumoto et al., 1996). Nevertheless, careful analysis has enabled, for example, the functions of IP 3 Rs in cerebellum in mice (Inoue et al., 1998) and phototransduction in Drosophila to be studied (Acharya et al., 1997;Raghu et al., 2000). Caenorhabditis elegans is also proving to be a powerful system for understanding IP 3 signaling function. IP 3 Rs i...

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“…The presence of intestine was also independently scored by the birefringence of gut granules under polarization optics (Laufer et al 1980). Embryos were then transferred in M9 to poly-L-lysine-coated slides for immunostaining.…”

Section: Laser Ablation and Lineage Analysismentioning

confidence: 99%

“…Each of the founder cells shows distinct rates of cell division and produces a unique repertoire of differentiated cell types. The ability to make endoderm appears to be restricted to the E blastomere by a series of asymmetric cell divisions that yield qualitatively different sister cells (Laufer et al 1980;Cowan and McIntosh 1985;Schierenberg and Wood 1985;Edgar and McGhee 1986). These observations suggested that the fate of E is controlled in part by regulatory factors that act cell autonomously.…”

mentioning

confidence: 99%

“…The nematode Caenorhabditis elegans provides an amenable molecular genetic system with which to study the mechanisms that specify the germ layers. The relatively simple pattern of development of the C. elegans endoderm, which gives rise to a single organ, the intestine, has made it the focus of a number of embryological, genetic, and molecular studies (e.g., Laufer et al 1980;Edgar and McGhee 1988;Aamodt et al 1991;Goldstein 1992).…”

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confidence: 99%

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end-1 encodes an apparent GATA factor that specifies the endoderm precursor in Caenorhabditis elegans embryos

Zhu¹,

Hill²,

Heid³

et al. 1997

Genes Dev.

208

203

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The endoderm in the nematode Caenorhabditis elegans is clonally derived from the E founder cell. We identified a single genomic region (the endoderm-determining region, or EDR) that is required for the production of the entire C. elegans endoderm. In embryos lacking the EDR, the E cell gives rise to ectoderm and mesoderm instead of endoderm and appears to adopt the fate of its cousin, the C founder cell. end-1, a gene from the EDR, restores endoderm production in EDR deficiency homozygotes. end-1 transcripts are first detectable specifically in the E cell, consistent with a direct role for end-1 in endoderm development. The END-1 protein is an apparent zinc finger-containing GATA transcription factor. As GATA factors have been implicated in endoderm development in other animals, our findings suggest that endoderm may be specified by molecularly conserved mechanisms in triploblastic animals. We propose that end-1, the first zygotic gene known to be involved in the specification of germ layer and founder cell identity in C. elegans, may link maternal genes that regulate the establishment of the endoderm to downstream genes responsible for endoderm differentiation.

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Segregation of developmental potential in early embryos of caenorhabditis elegans

Cited by 213 publications

References 12 publications

Reevaluation of the Role of the med-1 and med-2 Genes in Specifying the Caenorhabditis elegans Endoderm

Reevaluation of the Role of the med-1 and med-2 Genes in Specifying the Caenorhabditis elegans Endoderm

Regulated Disruption of Inositol 1,4,5-Trisphosphate Signaling inCaenorhabditis elegansReveals New Functions in Feeding and Embryogenesis

end-1 encodes an apparent GATA factor that specifies the endoderm precursor in Caenorhabditis elegans embryos

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