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[
Genome Res,
2005]
The Hedgehog (Hh) signaling pathway promotes pattern formation and cell proliferation in Drosophila and vertebrates. Hh is a ligand that binds and represses the Patched (Ptc) receptor and thereby releases the latent activity of the multipass membrane protein Smoothened (Smo), which is essential for transducing the Hh signal. In Caenorhabditis elegans, the Hh signaling pathway has undergone considerable divergence. Surprisingly, obvious Smo and Hh homologs are absent whereas PTC, PTC-related (PTR), and a large family of nematode Hh-related (Hh-r) proteins are present. We find that the number of PTC-related and Hh-r proteins has expanded in C. elegans, and that this expansion occurred early in Nematoda. Moreover, the function of these proteins appears to be conserved in Caenorhabditis briggsae. Given our present understanding of the Hh signaling pathway, the absence of Hh and Smo raises many questions about the evolution and the function of the PTC, PTR, and Hh-r proteins in C. elegans. To gain insights into their roles, we performed a global survey of the phenotypes produced by RNA-mediated interference (RNAi). Our study reveals that these genes do not require Smo for activity and that they function in multiple aspects of C. elegans development, including molting, cytokinesis, growth, and pattern formation. Moreover, a subset of the PTC, PTR, and Hh-r proteins have the same RNAi phenotypes, indicating that they have the potential to participate in the same processes.
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[
Sci Total Environ,
2023]
The increasing demand for rare earth elements (REEs) in modern applications has drawn significant attention. REEs can be introduced into the environment through REE-containing fertilizers, abandoned REE-rich equipment, and mining, persisting and impacting soil quality, nutrient cycles, and plant growth. Scientists have raised concerns about REEs entering the food chain from the environment and eventually accumulating in organisms. Decades of experimental evidence have shown that these effects include inhibited growth, impaired liver function, and alterations in children's intelligence quotients. However, there exists a paucity of research that has elucidated the metabolic-level biological impacts of REEs. In our study, Caenorhabditis elegans (C. elegans) was used as a model organism to investigate physiological and inherent metabolic changes under exposure to different concentrations of REEs. The diet bacteria of nematodes play a key role in their life and development. Therefore, we investigated the influence of bacterial activity on the nematodes' response to REE exposure. We observed a concentration-dependent accumulation of REEs in nematodes, which consequently led to a reduction in lifespan and alterations in body length. Exposure to a mixed solution of REEs, in comparison to a single REE solution, resulted in greater toxicity toward nematodes. The metabolic results showed that the above changes were closely related to REE-induced amino acid metabolism disorder, membrane disturbance, DNA damage, and oxidative stress. Of note, the presence of living bacteria elicits REE effects in C. elegans. These findings highlight the potential intrinsic metabolic changes occurring in nematodes under REE exposure. Our study raises awareness of the exposure risks associated with REEs, provides valuable insight into the metabolic-level biological impacts of REEs and contributes to the development of effective mitigation strategies to reduce potential risks to human health.
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[
Chemosphere,
2017]
Rare earth elements (REEs) are widely used in industry, agriculture, medicine and daily life in recent years. However, environmental and health risks of REEs are still poorly understood. In this study, neurotoxicity of trichloride neodymium, praseodymium and scandium were evaluated using nematode Caenorhabditis elegans as the assay system. Median lethal concentrations (48h) were 99.9, 157.2 and 106.4mg/L for NdCl3, PrCl3 and ScCl3, respectively. Sublethal dose (10-30mg/L) of these trichloride salts significantly inhibited body length of nematodes. Three REEs resulted in significant declines in locomotor frequency of body bending, head thrashing and pharyngeal pumping. In addition, mean speed and wavelength of crawling movement were significantly reduced after chronic exposure. Using transgenic nematodes, we found NdCl3, PrCl3 and ScCl3 resulted in loss of dendrite and soma of neurons, and induced down-expression of
dat-1::GFP and
unc-47::GFP. It indicates that REEs can lead to damage of dopaminergic and GABAergic neurons. Our data suggest that exposure to REEs may cause neurotoxicity of inducing behavioral deficits and neural damage. These findings provide useful information for understanding health risk of REE materials.
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[
BMC Genomics,
2008]
ABSTRACT: BACKGROUND: The Hedgehog (Hh) signaling pathway plays important roles in human and animal development as well as in carcinogenesis. Hh molecules have been found in both protostomes and deuterostomes, but curiously the nematode Caenorhabditis elegans lacks a bona-fide Hh. Instead a series of Hh-related proteins are found, which share the Hint/Hog domain with Hh, but have distinct N-termini. Results: We performed extensive genome searches such as the cnidarian Nematostella vectensis and several nematodes to gain further insights into Hh evolution. We found six genes in N. vectensis with a relationship to Hh: two Hh genes, one gene with a Hh N-terminal domain fused to a Willebrand factor type A domain (VWA), and three genes containing Hint/Hog domains with distinct novel N-termini. In the nematode Brugia malayi we find the same types of hh-related genes as in C. elegans. In the more distantly related Enoplea nematodes Xiphinema and Trichinella spiralis we find a bona-fide Hh. In addition, T. spiralis also has a quahog gene like C. elegans, and there are several additional hh-related genes, some of which have secreted N-terminal domains of only 15 to 25 residues. Examination of other Hh pathway components revealed that T. spiralis - like C. elegans - lacks some of these components. Extending our search to all eukaryotes, we recovered genes containing a Hog domain similar to Hh from many different groups of protists. In addition, we identified a novel Hint gene family present in many eukaryote groups that encodes a VWA domain fused to a distinct Hint domain we call Vint. Further members of a poorly characterized Hint family were also retrieved from bacteria. CONCLUSION: In Cnidaria and nematodes the evolution of hh genes occurred in parallel to the evolution of other genes that contain a Hog domain but have different N-termini. The fact that Hog genes comprising a secreted N-terminus and a Hog domain are also found in many protists suggests that this gene family must have arisen in very early eukaryotic evolution, which eventually gave rise to hh and hh-related genes in animals. The results indicate a hitherto unsuspected ability of Hog domain encoding genes to evolve new N-termini. In one instance in Cnidaria, the Hh N-terminal signaling domain is associated with a VWA domain and lacks a Hog domain, suggesting a modular mode of evolution also for the N-terminal domain. The Hog domain proteins, the inteins and VWA-Vint proteins represent three different families of Hint domain proteins that evolved in parallel in eukaryotesConclusion: In Cnidaria and nematodes the evolution of hh genes occurred in parallel to the evolution of other genes that contain a Hog domain but have different N-termini. The fact that Hog genes comprising a secreted N-terminus and a Hog domain are also found in many protists suggests that this gene family must have arisen in very early eukaryotic evolution, which eventually gave rise to hh and hh-related genes in animals. The results indicate a hitherto unsuspected ability of Hog domain encoding genes to evolve new N-termini. In one instance in Cnidaria, the Hh N-terminal signaling domain is associated with a VWA domain and lacks a Hog domain, suggesting a modular mode of evolution also for the N-terminal domain. The Hog domain proteins, the inteins and VWA-Vint proteins represent three different families of Hint domain proteins that evolved in parallel in eukaryotes.
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Ekker SC, Cotter RJ, Koonin EV, Ma Y, von Kessler DP, Beachy PA, Chen CH, Porter JA, Woods AS, Young KE, Park WJ
[
Cell,
1996]
Autocatalytic processing mediated by the carboxyterminal domain of the hedgehog (hh) protein precursor (Hh) generates an amino-terminal product that accounts for all known signaling activity. The role of autoprocessing biogenesis of the hh signal has been unclear, since a truncated unprocessed protein lacking all carboxy-terminal domain sequences retains signaling activity. Here, we present evidence that the autoprocessing reaction proceeds via an internal thioester intermediate and results in a covalent modification that increases the hydrophobic character of the signaling domain and influences its spatial and subcellular distribution. We demonstrate that truncated unprocessed amino-terminal protein causes embryonic mispatterning, even when expression is localized to cells that normally express Hh, thus suggesting a role for autoprocessing in spatial regulation of hh signaling. This type of processing also appears to operate in the biogenesis of other novel secreted proteins.
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[
WormBook,
2006]
In Drosophila and vertebrates, Hedgehog (Hh) signalling is mediated by a cascade of genes, which play essential roles in cell proliferation and survival, and in patterning of the embryo, limb buds and organs. In C. elegans, this pathway has undergone considerable evolutionary divergence; genes encoding homologues of key pathway members, including Hh, Smoothened, Cos2, Fused and Suppressor of Fused, are absent. Surprisingly, over sixty proteins (i.e. WRT, GRD, GRL, and QUA), encoded by a set of genes collectively referred to as the Hh-related genes, and two co-orthologs ( PTC-1 ,-3) of fly Patched, a Hh receptor, are present in C. elegans. Several of the Hh-related proteins are bipartite and all can potentially generate peptides with signalling activity, although none of these peptides shares obvious sequence similarity with Hh. In addition, the ptc -related ( ptr ) genes, which are present in a single copy in Drosophila and vertebrates and encode proteins closely related to Patched, have undergone an expansion in number in nematodes. A number of functions, including roles in molting, have been attributed to the C. elegans Hh-related, PTC and PTR proteins; most of these functions involve processes that are associated with the trafficking of proteins, sterols or sterol-modified proteins. Genes encoding other components of the Hh signalling pathway are also found in C. elegans, but their functions remain to be elucidated.
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[
Metallomics,
2010]
With their widespread applications in industry, agriculture and many other fields, more and more rare earth elements (REEs) are getting into the environment, especially the aquatic systems. Therefore, understanding the aquatic ecotoxicity of REEs has become more and more important. In the present work, Caenorhabditis elegans (C. elegans) was used as a test organism and life-cycle endpoints were chosen along with elemental assay to evaluate the aquatic toxicity of lanthanum (La), a representative of REEs. The results show La+ had significant adverse effects on the growth and reproduction of worms above a concentration of 10 mol L. The elemental mapping by microbeam synchrotron radiation X-ray fluorescence (-SRXRF) illustrated how La treatment disturbed the metals distribution in the whole body of a single tiny nematode at lower levels. Our results suggested that the high-level REEs in some polluted water bodies would lead to an aquatic ecological crisis. The assessment we performed in the present work could be developed as a standardized test design for aquatic toxicological research.
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[
East Coast Worm Meeting,
1998]
The Hedgehog family of signaling molecules controls many aspects of animal development, from embryonic patterning to limb formation. Recently, these proteins have been shown to rely on a novel mechanism to regulate their spatial distribution (1,2). Hedgehog proteins undergo an autoprocessing reaction to yield two distinct products, an amino-terminal fragment (Hh-N), and a carboxy-terminal fragment (Hh-C). Hh-N functions in signaling, whereas Hh-C mediates the processing reaction. This reaction proceeds via an internal thioester intermediate and results in the covalent linkage of cholesterol to Hh-N. This modification in turn causes Hh-N to remain tightly associated with the cell surface, thus effectively limiting its free diffusion and range of action. We are interested in determining whether similar mechanisms may be operating in the biogenesis of other secreted molecules. Towards this goal, we have started to characterize a set of eight C. elegans proteins with sequence similarity to the Hh-C domain of Hedgehog (2,3). In these proteins, as in the Hedgehog family, the Hh-C-like domain is located in the carboxy-teminal end, and is preceded by an amino-terminal domain bearing a signal sequence (but with otherwise no homology to Hh-N). This structure is consistent with the possibility that these proteins are secreted and undergo processing in a manner similar to that described for Hedgehog. To test this possibility we have fused the Hh-C-like domain of one of these proteins to a His tag, and purified the fusion protein from E. coli. We find that such a fusion can undergo the processing reaction in vitro, suggesting that the Hh-C-like domain is functionally active in the nematode proteins. We have begun to characterize the functions of Hh-C-related proteins using RNA-mediated interference. Our initial results suggest that one of these proteins, T05C12, is essential for molting. Injection of T05C12 double-stranded RNA results in 90% larval lethality. The larvae apparently die from a failure to shed old cuticles during molts. In many animals, a cuticular plug can be seen obstructing the mouth opening where it presumably interferes with feeding. The amino-terminal domain of T05C12 contains several sequence motifs similar to those found in collagens and other extracellular matrix proteins, raising the possibility that the T05C12 product is a cuticle component. Consistent with this possibility, a T05C12:GFP fusion is expressed in hypodermal cells during larval and adult stages. We are currently determining the effects of expressing mutant forms of T05C12 to test the function of its Hh-C-like domain. 1. Porter, JA. et al. (1996). Cell 86, 21-34. 2. Porter, JA. et al. (1996). Science 274, 255-259. 3. Burglin, TR. (1996). Current Biology 6, 1047-1050.
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[
Biochem J,
1999]
The cAMP-dependent protein kinase (protein kinase A, PK-A) is multifunctional in nature, with key roles in the control of diverse aspects of eukaryotic cellular activity. In the case of the free-living nematode, Caenorhabditis elegans, a gene encoding the PK-A catalytic subunit has been identified and two isoforms of this subunit, arising from a C-terminal alternative-splicing event, have been characterized [Gross, Bagchi, Lu and Rubin (1990) J. Biol. Chem. 265, 6896-6907]. Here we report the occurrence of N-terminal alternative-splicing events that, in addition to generating a multiplicity of non-myristoylatable isoforms, also generate the myristoylated variant(s) of the catalytic subunit that we have recently characterized [Aspbury, Fisher, Rees and Clegg (1997) Biochem. Biophys. Res. Commun. 238, 523-527]. The gene spans more than 36 kb and is divided into a total of 13 exons. Each of the mature transcripts contains only 7 exons. In addition to the already characterized exon 1, the 5'-untranslated region and first intron actually contain 5 other exons, any one of which may be alternatively spliced on to exon 2 at the 5' end of the pre-mRNA. This N-terminal alternative splicing occurs in combination with either of the already characterized C-terminal alternative exons. Thus, C. elegans expresses at least 12 different isoforms of the catalytic subunit of PK-A. The significance of this unprecedented structural diversity in the family of PK-A catalytic subunits is discussed.
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[
Genome Res,
1999]
Previously, we have described novel families of genes, warthog (wrt) and groundhog (grd), in Caenorhabditis elegans. They are related to Hedgehog (Hh) through the carboxy-terminal autoprocessing domain (called Hog or Hint). A comprehensive survey revealed 10 genes with Hog/Hint modules in C. elegans. Five of these are associated with a Wart domain in wrt genes, and three with multiple copies of the Ground domain in grd genes. Both the Wart domain and the Ground domain occur also in genes encoding no Hog domain. Further, we define a new group of genes related to the grd genes, called ground-like (grl). Overall, C. elegans has more than 50 genes belonging to these gene families. Phylogenetic and sequence analysis shows that the wrt, grd, and grl genes are derived from each other. Further examination reveals a sequence motif with similarity to the core of the amino-terminal-signaling domain of Hh proteins. Our data suggest that the wrt, grd, grl, and hh genes are derived from a single ancestral gene. wrt, grd, and grl genes are also present in other nematodes, but so far not in any other phyla. Conversely, hh is not found presently in C. elegans nor other nematodes. Thus, the nematode genes could be the homologs of Hh molecules in other phyla. The membrane molecule Patched has been shown previously to be a receptor of Hh. Many Patched-related proteins are present in C. elegans, which may be targets of the hh-related genes. No Hedgehog-interacting protein (Hip) was found. We analyzed the expression patterns of eight wrt and eight grd genes. The results show that some closely related genes are expressed in the same tissues, but, overall, the expression patterns are diverse, comprising hypodermis, seam cells, the excretory cell, sheath and socket cells, and different types of neurons.