Limits...
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.

Show MeSH

Related in: MedlinePlus

Ss-age-1 is expressed in amphidial neurons, the intestine, and other tissues.Fluorescence (A,C) and DIC (B,D) images of transgenic S. stercoralis post-free-living first-stage larvae expressing Ss-age-1p::egfp::Ss-era-1t from an extra-chromosomal array. (A,B) Expression of the EGFP reporter was present in the intestine (i), gonadal primordium (g), amphidial/head neuron (a), hypodermis (h), and phasmidial/tail neuron (p). (C,D) Expression of the EGFP reporter was present in an amphidial neuron (long arrow), with positional homology to AWC in C. elegans. The other cell body of the amphidial neuron pair is out of the plane of focus (short arrow). Cell bodies of the amphidial neurons align just lateral to the black lines in panel D [74]. Scale bars = 100 µm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3368883&req=5

pone-0038587-g004: Ss-age-1 is expressed in amphidial neurons, the intestine, and other tissues.Fluorescence (A,C) and DIC (B,D) images of transgenic S. stercoralis post-free-living first-stage larvae expressing Ss-age-1p::egfp::Ss-era-1t from an extra-chromosomal array. (A,B) Expression of the EGFP reporter was present in the intestine (i), gonadal primordium (g), amphidial/head neuron (a), hypodermis (h), and phasmidial/tail neuron (p). (C,D) Expression of the EGFP reporter was present in an amphidial neuron (long arrow), with positional homology to AWC in C. elegans. The other cell body of the amphidial neuron pair is out of the plane of focus (short arrow). Cell bodies of the amphidial neurons align just lateral to the black lines in panel D [74]. Scale bars = 100 µm.

Mentions: To determine the anatomical expression pattern of Ss-age-1, we transformed parental free-living S. stercoralis females with a construct fusing 1.3 kb of Ss-age-1 5′ region to egfp, along with an Ss-act-2p::mRFPmars co-injection marker, as previously described [7]. Injected females were paired with S. stercoralis males, and their post-free-living L1 progeny were screened for fluorescence. Of the more than 1,000 F1 larvae screened, 55 transgenic larvae expressing EGFP were observed. Each transgenic L1 was imaged at 400x magnification and scored for fluorescence in several tissues (Table 1). Strong EGFP expression was most frequently observed in the anterior intestine, gonadal primordium, amphidial/head neurons, and phasmidial/tail neurons (Figure 4A–D). Consistent with the observed strong intestinal expression, a search of the 1.3 kb region upstream of the Ss-age-1 translational start site for ELT-2 recognition motifs [66] revealed two consensus TGATAA motifs 136 bp and 630 bp upstream of the start site.


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)

Ss-age-1 is expressed in amphidial neurons, the intestine, and other tissues.Fluorescence (A,C) and DIC (B,D) images of transgenic S. stercoralis post-free-living first-stage larvae expressing Ss-age-1p::egfp::Ss-era-1t from an extra-chromosomal array. (A,B) Expression of the EGFP reporter was present in the intestine (i), gonadal primordium (g), amphidial/head neuron (a), hypodermis (h), and phasmidial/tail neuron (p). (C,D) Expression of the EGFP reporter was present in an amphidial neuron (long arrow), with positional homology to AWC in C. elegans. The other cell body of the amphidial neuron pair is out of the plane of focus (short arrow). Cell bodies of the amphidial neurons align just lateral to the black lines in panel D [74]. Scale bars = 100 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368883&req=5

pone-0038587-g004: Ss-age-1 is expressed in amphidial neurons, the intestine, and other tissues.Fluorescence (A,C) and DIC (B,D) images of transgenic S. stercoralis post-free-living first-stage larvae expressing Ss-age-1p::egfp::Ss-era-1t from an extra-chromosomal array. (A,B) Expression of the EGFP reporter was present in the intestine (i), gonadal primordium (g), amphidial/head neuron (a), hypodermis (h), and phasmidial/tail neuron (p). (C,D) Expression of the EGFP reporter was present in an amphidial neuron (long arrow), with positional homology to AWC in C. elegans. The other cell body of the amphidial neuron pair is out of the plane of focus (short arrow). Cell bodies of the amphidial neurons align just lateral to the black lines in panel D [74]. Scale bars = 100 µm.
Mentions: To determine the anatomical expression pattern of Ss-age-1, we transformed parental free-living S. stercoralis females with a construct fusing 1.3 kb of Ss-age-1 5′ region to egfp, along with an Ss-act-2p::mRFPmars co-injection marker, as previously described [7]. Injected females were paired with S. stercoralis males, and their post-free-living L1 progeny were screened for fluorescence. Of the more than 1,000 F1 larvae screened, 55 transgenic larvae expressing EGFP were observed. Each transgenic L1 was imaged at 400x magnification and scored for fluorescence in several tissues (Table 1). Strong EGFP expression was most frequently observed in the anterior intestine, gonadal primordium, amphidial/head neurons, and phasmidial/tail neurons (Figure 4A–D). Consistent with the observed strong intestinal expression, a search of the 1.3 kb region upstream of the Ss-age-1 translational start site for ELT-2 recognition motifs [66] revealed two consensus TGATAA motifs 136 bp and 630 bp upstream of the start site.

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