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The HLH-6 transcription factor regulates C. elegans pharyngeal gland development and function.

Smit RB, Schnabel R, Gaudet J - PLoS Genet. (2008)

Bottom Line: Interestingly, hlh-6 mutants are also feeding defective, ascribing a biological function for the glands.Pharyngeal pumping in hlh-6 mutants is normal, but hlh-6 mutants lack expression of a class of mucin-related proteins that are normally secreted by pharyngeal glands and line the pharyngeal cuticle.An interesting possibility is that one function of pharyngeal glands is to secrete a pharyngeal lining that ensures efficient transport of food along the pharyngeal lumen.

View Article: PubMed Central - PubMed

Affiliation: Genes and Development Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada.

ABSTRACT
The Caenorhabditis elegans pharynx (or foregut) functions as a pump that draws in food (bacteria) from the environment. While the "organ identity factor" PHA-4 is critical for formation of the C. elegans pharynx as a whole, little is known about the specification of distinct cell types within the pharynx. Here, we use a combination of bioinformatics, molecular biology, and genetics to identify a helix-loop-helix transcription factor (HLH-6) as a critical regulator of pharyngeal gland development. HLH-6 is required for expression of a number of gland-specific genes, acting through a discrete cis-regulatory element named PGM1 (Pharyngeal Gland Motif 1). hlh-6 mutants exhibit a frequent loss of a subset of glands, while the remaining glands have impaired activity, indicating a role for hlh-6 in both gland development and function. Interestingly, hlh-6 mutants are also feeding defective, ascribing a biological function for the glands. Pharyngeal pumping in hlh-6 mutants is normal, but hlh-6 mutants lack expression of a class of mucin-related proteins that are normally secreted by pharyngeal glands and line the pharyngeal cuticle. An interesting possibility is that one function of pharyngeal glands is to secrete a pharyngeal lining that ensures efficient transport of food along the pharyngeal lumen.

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hlh-6 is expressed in pharyngeal glands.(A) Schematic of the genomic region containing hlh-6. The position of the deletion allele tm299 is indicated. The portion of hlh-6 encoding the DNA Binding Domain (DBD) is shown as is the hlh-6 “minigene”, which rescues all aspects of the hlh-6 mutant phenotype. (B) Expression of the hlh-6::YFP reporter, containing 1175 bp (of 1190 bp) of intergenic sequence from the ATG of hlh-6 to just downstream of the stop codon of the next upstream gene, T15H9.2. Anterior is at left and the pharynx is outlined. Scale bar represents 10 µm.
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pgen-1000222-g003: hlh-6 is expressed in pharyngeal glands.(A) Schematic of the genomic region containing hlh-6. The position of the deletion allele tm299 is indicated. The portion of hlh-6 encoding the DNA Binding Domain (DBD) is shown as is the hlh-6 “minigene”, which rescues all aspects of the hlh-6 mutant phenotype. (B) Expression of the hlh-6::YFP reporter, containing 1175 bp (of 1190 bp) of intergenic sequence from the ATG of hlh-6 to just downstream of the stop codon of the next upstream gene, T15H9.2. Anterior is at left and the pharynx is outlined. Scale bar represents 10 µm.

Mentions: To examine the involvement of hlh-6 in PGM1 activity, we first determined the expression of a transcriptional reporter that included almost all intergenic sequence (1175 bp of 1190 bp) between hlh-6 and its nearest upstream neighbour, T15H9.2. We found that hlh-6::YFP was expressed strongly and specifically in the pharyngeal glands (98% of transgenics), with occasional (12%), weak expression in the pharyngeal neuron I3 (Figure 3). Expression was first detectable shortly after the terminal cell division that gives rise to pharyngeal glands (bean stage embryos) and persisted throughout the life cycle in all five pharyngeal glands. Because PGM1 and hlh-6 both appear to be active in pharyngeal glands and because PGM1 contains a bHLH binding site, we hypothesized that HLH-6 is the cognate trans-acting factor for PGM1.


The HLH-6 transcription factor regulates C. elegans pharyngeal gland development and function.

Smit RB, Schnabel R, Gaudet J - PLoS Genet. (2008)

hlh-6 is expressed in pharyngeal glands.(A) Schematic of the genomic region containing hlh-6. The position of the deletion allele tm299 is indicated. The portion of hlh-6 encoding the DNA Binding Domain (DBD) is shown as is the hlh-6 “minigene”, which rescues all aspects of the hlh-6 mutant phenotype. (B) Expression of the hlh-6::YFP reporter, containing 1175 bp (of 1190 bp) of intergenic sequence from the ATG of hlh-6 to just downstream of the stop codon of the next upstream gene, T15H9.2. Anterior is at left and the pharynx is outlined. Scale bar represents 10 µm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2563036&req=5

pgen-1000222-g003: hlh-6 is expressed in pharyngeal glands.(A) Schematic of the genomic region containing hlh-6. The position of the deletion allele tm299 is indicated. The portion of hlh-6 encoding the DNA Binding Domain (DBD) is shown as is the hlh-6 “minigene”, which rescues all aspects of the hlh-6 mutant phenotype. (B) Expression of the hlh-6::YFP reporter, containing 1175 bp (of 1190 bp) of intergenic sequence from the ATG of hlh-6 to just downstream of the stop codon of the next upstream gene, T15H9.2. Anterior is at left and the pharynx is outlined. Scale bar represents 10 µm.
Mentions: To examine the involvement of hlh-6 in PGM1 activity, we first determined the expression of a transcriptional reporter that included almost all intergenic sequence (1175 bp of 1190 bp) between hlh-6 and its nearest upstream neighbour, T15H9.2. We found that hlh-6::YFP was expressed strongly and specifically in the pharyngeal glands (98% of transgenics), with occasional (12%), weak expression in the pharyngeal neuron I3 (Figure 3). Expression was first detectable shortly after the terminal cell division that gives rise to pharyngeal glands (bean stage embryos) and persisted throughout the life cycle in all five pharyngeal glands. Because PGM1 and hlh-6 both appear to be active in pharyngeal glands and because PGM1 contains a bHLH binding site, we hypothesized that HLH-6 is the cognate trans-acting factor for PGM1.

Bottom Line: Interestingly, hlh-6 mutants are also feeding defective, ascribing a biological function for the glands.Pharyngeal pumping in hlh-6 mutants is normal, but hlh-6 mutants lack expression of a class of mucin-related proteins that are normally secreted by pharyngeal glands and line the pharyngeal cuticle.An interesting possibility is that one function of pharyngeal glands is to secrete a pharyngeal lining that ensures efficient transport of food along the pharyngeal lumen.

View Article: PubMed Central - PubMed

Affiliation: Genes and Development Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada.

ABSTRACT
The Caenorhabditis elegans pharynx (or foregut) functions as a pump that draws in food (bacteria) from the environment. While the "organ identity factor" PHA-4 is critical for formation of the C. elegans pharynx as a whole, little is known about the specification of distinct cell types within the pharynx. Here, we use a combination of bioinformatics, molecular biology, and genetics to identify a helix-loop-helix transcription factor (HLH-6) as a critical regulator of pharyngeal gland development. HLH-6 is required for expression of a number of gland-specific genes, acting through a discrete cis-regulatory element named PGM1 (Pharyngeal Gland Motif 1). hlh-6 mutants exhibit a frequent loss of a subset of glands, while the remaining glands have impaired activity, indicating a role for hlh-6 in both gland development and function. Interestingly, hlh-6 mutants are also feeding defective, ascribing a biological function for the glands. Pharyngeal pumping in hlh-6 mutants is normal, but hlh-6 mutants lack expression of a class of mucin-related proteins that are normally secreted by pharyngeal glands and line the pharyngeal cuticle. An interesting possibility is that one function of pharyngeal glands is to secrete a pharyngeal lining that ensures efficient transport of food along the pharyngeal lumen.

Show MeSH