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Strongyloides stercoralis age-1: a potential regulator of infective larval development in a parasitic nematode.

Stoltzfus JD, Massey HC, Nolan TJ, Griffith SD, Lok JB - PLoS ONE (2012)

Bottom Line: We observed conservation of expression in amphidial neurons, which play a critical role in developmental regulation of both dauer larvae and L3i.Application of the PI3 kinase inhibitor LY294002 suppressed L3i in vitro activation in a dose-dependent fashion, with 100 µM resulting in a 90% decrease (odds ratio: 0.10, 95% confidence interval: 0.08-0.13) in the odds of resumption of feeding for treated L3i in comparison to the control.Together, these data support the hypothesis that Ss-age-1 regulates the development of S. stercoralis L3i via an IIS pathway in a manner similar to that observed in C. elegans dauer larvae.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathobiology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, United States of America.

ABSTRACT
Infective third-stage larvae (L3i) of the human parasite Strongyloides stercoralis share many morphological, developmental, and behavioral attributes with Caenorhabditis elegans dauer larvae. The 'dauer hypothesis' predicts that the same molecular genetic mechanisms control both dauer larval development in C. elegans and L3i morphogenesis in S. stercoralis. In C. elegans, the phosphatidylinositol-3 (PI3) kinase catalytic subunit AGE-1 functions in the insulin/IGF-1 signaling (IIS) pathway to regulate formation of dauer larvae. Here we identify and characterize Ss-age-1, the S. stercoralis homolog of the gene encoding C. elegans AGE-1. Our analysis of the Ss-age-1 genomic region revealed three exons encoding a predicted protein of 1,209 amino acids, which clustered with C. elegans AGE-1 in phylogenetic analysis. We examined temporal patterns of expression in the S. stercoralis life cycle by reverse transcription quantitative PCR and observed low levels of Ss-age-1 transcripts in all stages. To compare anatomical patterns of expression between the two species, we used Ss-age-1 or Ce-age-1 promoter::enhanced green fluorescent protein reporter constructs expressed in transgenic animals for each species. We observed conservation of expression in amphidial neurons, which play a critical role in developmental regulation of both dauer larvae and L3i. Application of the PI3 kinase inhibitor LY294002 suppressed L3i in vitro activation in a dose-dependent fashion, with 100 µM resulting in a 90% decrease (odds ratio: 0.10, 95% confidence interval: 0.08-0.13) in the odds of resumption of feeding for treated L3i in comparison to the control. Together, these data support the hypothesis that Ss-age-1 regulates the development of S. stercoralis L3i via an IIS pathway in a manner similar to that observed in C. elegans dauer larvae. Understanding the mechanisms by which infective larvae are formed and activated may lead to novel control measures and treatments for strongyloidiasis and other soil-transmitted helminthiases.

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Ce-age-1 is expressed in amphidial neurons and other tissues.Fluorescence (A,C) and DIC (B,D) images of transgenic C. elegans first-stage larvae expressing Ce-age-1p::Ce-age-1(102bp) ::egfp::Ce-age-1t from an extra-chromosomal array. (A,B) Strong expression of the EGFP reporter was present in amphidial neurons (a), a neuron or support cell anterior to the nerve ring (c), and the sphincter connecting the pharynx to the intestine (s). Weak expression was present in the intestine (i), hypodermis (h), and a phasmidial neuron (p). (C,D) EGFP reporter expression was present in the amphidial neurons AWC (short arrow) and ASJ (long arrow). Cell bodies of the amphidial neurons align just lateral to the black lines in panel D [74]. Scale bars = 100 µm.
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pone-0038587-g003: Ce-age-1 is expressed in amphidial neurons and other tissues.Fluorescence (A,C) and DIC (B,D) images of transgenic C. elegans first-stage larvae expressing Ce-age-1p::Ce-age-1(102bp) ::egfp::Ce-age-1t from an extra-chromosomal array. (A,B) Strong expression of the EGFP reporter was present in amphidial neurons (a), a neuron or support cell anterior to the nerve ring (c), and the sphincter connecting the pharynx to the intestine (s). Weak expression was present in the intestine (i), hypodermis (h), and a phasmidial neuron (p). (C,D) EGFP reporter expression was present in the amphidial neurons AWC (short arrow) and ASJ (long arrow). Cell bodies of the amphidial neurons align just lateral to the black lines in panel D [74]. Scale bars = 100 µm.

Mentions: In all six lines, we observed strong EGFP fluorescence in two pairs of amphidial neurons and their dendritic processes, a pair of inter-neurons or support cells anterior to the nerve ring, and the sphincter connecting the pharynx to the intestine (Figure 3A–D). We also noted variable expression in the hypodermis and the intestine between lines, with some lines having moderate expression in these tissues and others having little or no expression. Weak expression in a phasmidial neuron was observed in a minority of worms in each line. This led us to conclude that the main regulatory elements controlling anatomical expression of Ce-age-1 are located in the putative promoter region and not in the 5′ coding sequence or 3′ region.


Strongyloides stercoralis age-1: a potential regulator of infective larval development in a parasitic nematode.

Stoltzfus JD, Massey HC, Nolan TJ, Griffith SD, Lok JB - PLoS ONE (2012)

Ce-age-1 is expressed in amphidial neurons and other tissues.Fluorescence (A,C) and DIC (B,D) images of transgenic C. elegans first-stage larvae expressing Ce-age-1p::Ce-age-1(102bp) ::egfp::Ce-age-1t from an extra-chromosomal array. (A,B) Strong expression of the EGFP reporter was present in amphidial neurons (a), a neuron or support cell anterior to the nerve ring (c), and the sphincter connecting the pharynx to the intestine (s). Weak expression was present in the intestine (i), hypodermis (h), and a phasmidial neuron (p). (C,D) EGFP reporter expression was present in the amphidial neurons AWC (short arrow) and ASJ (long arrow). Cell bodies of the amphidial neurons align just lateral to the black lines in panel D [74]. Scale bars = 100 µm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3368883&req=5

pone-0038587-g003: Ce-age-1 is expressed in amphidial neurons and other tissues.Fluorescence (A,C) and DIC (B,D) images of transgenic C. elegans first-stage larvae expressing Ce-age-1p::Ce-age-1(102bp) ::egfp::Ce-age-1t from an extra-chromosomal array. (A,B) Strong expression of the EGFP reporter was present in amphidial neurons (a), a neuron or support cell anterior to the nerve ring (c), and the sphincter connecting the pharynx to the intestine (s). Weak expression was present in the intestine (i), hypodermis (h), and a phasmidial neuron (p). (C,D) EGFP reporter expression was present in the amphidial neurons AWC (short arrow) and ASJ (long arrow). Cell bodies of the amphidial neurons align just lateral to the black lines in panel D [74]. Scale bars = 100 µm.
Mentions: In all six lines, we observed strong EGFP fluorescence in two pairs of amphidial neurons and their dendritic processes, a pair of inter-neurons or support cells anterior to the nerve ring, and the sphincter connecting the pharynx to the intestine (Figure 3A–D). We also noted variable expression in the hypodermis and the intestine between lines, with some lines having moderate expression in these tissues and others having little or no expression. Weak expression in a phasmidial neuron was observed in a minority of worms in each line. This led us to conclude that the main regulatory elements controlling anatomical expression of Ce-age-1 are located in the putative promoter region and not in the 5′ coding sequence or 3′ region.

Bottom Line: We observed conservation of expression in amphidial neurons, which play a critical role in developmental regulation of both dauer larvae and L3i.Application of the PI3 kinase inhibitor LY294002 suppressed L3i in vitro activation in a dose-dependent fashion, with 100 µM resulting in a 90% decrease (odds ratio: 0.10, 95% confidence interval: 0.08-0.13) in the odds of resumption of feeding for treated L3i in comparison to the control.Together, these data support the hypothesis that Ss-age-1 regulates the development of S. stercoralis L3i via an IIS pathway in a manner similar to that observed in C. elegans dauer larvae.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathobiology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, United States of America.

ABSTRACT
Infective third-stage larvae (L3i) of the human parasite Strongyloides stercoralis share many morphological, developmental, and behavioral attributes with Caenorhabditis elegans dauer larvae. The 'dauer hypothesis' predicts that the same molecular genetic mechanisms control both dauer larval development in C. elegans and L3i morphogenesis in S. stercoralis. In C. elegans, the phosphatidylinositol-3 (PI3) kinase catalytic subunit AGE-1 functions in the insulin/IGF-1 signaling (IIS) pathway to regulate formation of dauer larvae. Here we identify and characterize Ss-age-1, the S. stercoralis homolog of the gene encoding C. elegans AGE-1. Our analysis of the Ss-age-1 genomic region revealed three exons encoding a predicted protein of 1,209 amino acids, which clustered with C. elegans AGE-1 in phylogenetic analysis. We examined temporal patterns of expression in the S. stercoralis life cycle by reverse transcription quantitative PCR and observed low levels of Ss-age-1 transcripts in all stages. To compare anatomical patterns of expression between the two species, we used Ss-age-1 or Ce-age-1 promoter::enhanced green fluorescent protein reporter constructs expressed in transgenic animals for each species. We observed conservation of expression in amphidial neurons, which play a critical role in developmental regulation of both dauer larvae and L3i. Application of the PI3 kinase inhibitor LY294002 suppressed L3i in vitro activation in a dose-dependent fashion, with 100 µM resulting in a 90% decrease (odds ratio: 0.10, 95% confidence interval: 0.08-0.13) in the odds of resumption of feeding for treated L3i in comparison to the control. Together, these data support the hypothesis that Ss-age-1 regulates the development of S. stercoralis L3i via an IIS pathway in a manner similar to that observed in C. elegans dauer larvae. Understanding the mechanisms by which infective larvae are formed and activated may lead to novel control measures and treatments for strongyloidiasis and other soil-transmitted helminthiases.

Show MeSH
Related in: MedlinePlus