Bouffard, J. et al. (2017) International Worm Meeting "SPV-1, a RhoGAP with an F-BAR domain, regulates calcium signaling in the C. elegans spermatheca during ovulation events."

Bouffard, J., Zaidel-Bar, R., Cram, E.

[International Worm Meeting, 2017]

The spermatheca is a 24-cell tube in the middle of the C. elegans reproductive system that functions as the site of fertilization, undergoing rounds of extreme stretch to accommodate entering oocytes followed by contraction to expel the fertilized egg. The contractility of the spermatheca is tightly regulated at the actomyosin level by calcium signaling and Rho activity. Many smooth muscle and non-muscle systems in other animals also exhibit actomyosin contractility regulated by calcium signaling and Rho activity, making the spermatheca a powerful model to study fundamental biological mechanisms regulating contractile tubes. SPV-1, a RhoGAP with an F-BAR domain, has emerged as a key regulator of contractility in the spermatheca. When spv-1 is lost, the spermatheca contracts immediately upon oocyte entry, leading to faster egg transit and perturbed egg shapes. Calcium signaling has been shown to drive contraction in the spermatheca, so we used the genetically encoded calcium sensor GCaMP expressed in the cells of the spermatheca to determine if the loss of spv-1 alters calcium signaling. Using widefield fluorescence microscopy, we monitored calcium activity in the spermatheca during ovulation events. We find that the loss of spv-1 results in a more rapid onset of calcium signaling upon oocyte entry, and elevated calcium levels throughout ovulation events. Overexpressing spv-1::mApple results in the expected opposite calcium phenotype, with slower onset of calcium signaling upon oocyte entry and decreased calcium levels throughout ovulation events. In addition to altered calcium levels, mutants with altered levels of spv-1 also lack proper spatiotemporal regulation of calcium signaling. High levels of SPV-1 result in retention of the embryo in the spermatheca, and preliminary data suggests that SPV-1 acts in a dose dependent manner to regulate the baseline calcium level. Studies using a mutated spv-1 which lacks RhoGAP activity exhibit calcium signaling similar to the loss of spv-1, suggesting that spv-1 controls calcium signaling primarily through GTPase activity. Previous work established that contractility of the spermatheca is carefully regulated by calcium signaling and RhoA activity. This work suggests that there is significant crosstalk between these two regulatory networks. Ongoing work aims to identify effectors that SPV-1 uses to regulate calcium signaling, and to use quantitative microscopy and analysis to more deeply understand how SPV-1 is modulating calcium signaling.

Natarajan L et al. (2000) East Coast Worm Meeting "Structure-function characterization of BAR-1 and other b -catenins in C. elegans"

Eisenmann DM, Natarajan L

[East Coast Worm Meeting, 2000]

C. elegans vulval development is co-ordinated by conserved RTK/Ras and Notch signaling pathways, so that six Vulval Precursor Cells (VPCs) adopt cell fates in the pattern 3/F 3 2 1 2 3 (F stands for Fused fate). In a screen for mutants affecting vulval development, bar-1 was identified. bar-1 mutants show defects in VPC and P12 cell fate specification and QL progeny migration. In each case, bar-1 is required to maintain Hox gene expression in the affected cells. bar-1 encodes a C. elegans b -catenin/Armadillo homolog. These proteins function in both cell adhesion and Wnt signal transduction. Wnt pathways regulate Hox genes in other systems and Wnt pathway mutants in C. elegans show similar phenotypes as bar-1 mutants which suggests that bar-1 acts in a Wnt pathway in the vulva. We would like to further understand BAR-1 structure and function. To identify transcriptional activation domains in BAR-1, regions of BAR-1 were made as GAL4 DBD fusions and tested in yeast. N-terminal and the C-terminal regions of BAR-1 possess transcriptional activating function, similar to other b -catenins. The effects of deletion of different BAR-1 domains on BAR-1 activity in the worm will be analyzed. A single region containing Armadillo repeats (1-9) did not activate transcription on its own and was used to identify BAR-1 interacting factors (143) by the yeast two hybrid method. The roles of potential interactors in vulval development are being investigated. BAR-1 is also being tested for interaction with other known Wnt pathway components in C. elegans. APR-1 and POP-1 interact with BAR-1 and reducing the activity of these genes results in vulval defects (work from our lab and Hajnal lab). BAR-1 does not interact with EGL-27, LIN-25 and HMP-1 (a -catenin) in yeast. C. elegans has three b -catenins, HMP-2, WRM-1 and BAR-1, as opposed to one (Armadillo) in Drosophila. WRM-1 functions in Wnt signaling in embryogenesis and HMP-2 in cell adhesion/morphogenesis. We are testing if BAR-1 function in the vulva can be substituted by fly Armadillo and other b -catenins in C. elegans. We would also like to know if BAR-1 interacting proteins can interact with WRM-1 and HMP-2. These experiments will help us understand if the functions of b-catenins in C. elegans have been conserved.

Lakshmi Natarajan et al. (2002) East Coast Worm Meeting "Characterizing bar-1 function and regulation during C. elegans vulval development"

David M Eisenmann, Lakshmi Natarajan

[East Coast Worm Meeting, 2002]

bar-1 was identified in a screen for mutants affecting vulval development. In bar-1 mutants, the Vulval Precursor Cells (VPCs) show defects in cell fate specification and adopt Fused fates more often than in wild-type animals. bar-1 was cloned and found to encode a C. elegans homolog of the -catenin/Armadillo family of proteins that have two functions: cell adhesion and Wnt signaling. bar-1 is required to maintain levels of lin-39Hox in the VPCs and mab-5Hox in the Q neuroblasts to enable these cells to adopt correct cell fates, suggesting a role for bar-1 in Wnt signaling. pry-1, an Axin homolog and a negative regulator of Wnt signaling, functions upstream of bar-1 in the above processes. pry-1 mutants display phenotypes associated with overactivation of the Wnt pathway and hence would be a good tool to isolate suppressors that could potentially identify other genes functioning in Wnt signaling in these processes. We have identified six suppressors from screening 5000 haploid genomes. We are in the process of characterizing the phenotypes of these suppressors and will determine if any of them are bar-1alleles. In addition to bar-1(ga80) isolated in our lab, there are seven more alleles of bar-1 that were isolated from screens done in the Kenyon lab and have not been further characterized. Efforts are underway to determine the nature of mutations in these alleles that leads to differences in severity of phenotypes amongst them. We know from work in our lab and others that bar-1 functions through a Wnt signaling pathway to enable the VPCs to adopt correct cell fates. However, we know very little about how bar-1 is regulated in the vulva to begin with. We used a series of bar-1 promoter deletions made as transcriptional GFP fusions to determine the spatio-temporal expression patterns in the vulva and other places. Using the above analysis, we found a 1.1 kb piece of the bar-1 promoter that was sufficient to drive bar-1expression in the VPCs and another 1.1 kb piece that is sufficient to drive expression in the ventral cord neurons. We are in the process of analyzing smaller deletions within these 1.1 kb regions to find minimal enhancer elements required for expression in the VPCs and ventral cord neurons in the hope of identifying transcription factors that bind to these sites and regulate bar-1 activity in vivo.

Eisenmann DM et al. (1997) International C. elegans Meeting "BAR-1 ENCODES A beta-CATENIN/ARMADILLO-RELATED PROTEIN FUNCTIONING IN VULVAL DEVELOPMENT"

Eisenmann DM, Kim SK

[International C. elegans Meeting, 1997]

We are interested in how the initially-equivalent vulval precursor cells (VPCs) become different from each other and adopt distinct cell fates during vulval development. We are studying how a b-catenin/armadillo-related protein (BAR-1) functions in this process. b-catenin/armadillo proteins function in cell adhesion and in Wnt signaling pathways. We identified the bar-1 gene in a screen for mutations that result in defective vulval induction (WBG 13.1, p69), and were surprised to find that this gene (then called pvl-1; 1996 WCWM) encodes a b-catenin/armadillo homolog. In bar-1 mutants, the VPCs do not adopt their cell fates correctly; P3.p-P8.p often remain undivided rather than adopting the 1!, 2! or 3!!fate. This bar-1 underinduced phenotype is epistatic to the Muv phenotype caused by let-60(gf) and mpk-1(gf) mutations but not lin-1(lf) and lin-31(lf) mutations. This result suggests that bar-1 may act downstream of the let-60 ras/mpk-1 MAP kinase pathway. BAR-1 is found in the cytoplasm and nucleus of the VPCs and other cells, but is not localized at cell junctions. This suggests that BAR-1 may have a function in cell signaling but not cell adhesion. Based on 1) the similarity of various bar-1 mutant phenotypes to those caused by mutations in the Hox genes lin-39, mab-5 and egl-5, (Maloof, Clandinin, 1996 WCWM; J. Maloof, pers. comm.), and 2) the fact that anti-sense expression in the vulva of a C. elegans APC-related gene gives a bar-1 like phenotype (A. Hajnal, unpublished), our current model is that bar-1 is a component of a Wnt signaling pathway that functions with Hox genes during the generation of the VPCs or in the specification of VPC fates.

Chan, Wesley et al. (2021) International Worm Meeting "BAR-1/beta-catenin and PRY-1/Axin show asymmetric and complementary expression in neuroblasts during C. elegans ventral nerve cord assembly"

Colavita, Antonio, Murray, John, Roenspies, Tony, Evans, Justin, Preston, Elicia, Chan, Wesley

[International Worm Meeting, 2021]

During embryogenesis DD, DA, and DB neuroblasts arise from left and right lineages, move towards the midline and intercalate into a single tract to form the ventral nerve cord (VNC). VNC assembly involves rosette-mediated convergent extension and planar cell polarity (PCP) and Robo pathways [1]. Disruption of this process results in the mispositioning, usually manifested as an anterior displacement, of embryonically-derived motor neurons in the VNC. A more recent analysis of canonical Wnt pathway components also revealed motor neuron position defects. The six DD neurons are evenly spaced along the anterior-posterior (AP) axis and therefore a convenient marker of VNC assembly. We found that mutations in bar-1/beta-catenin and pop-1/TCF display DD spacing defects. For example, in bar-1 and pop-1 mutants, DD2 is displaced anteriorly and therefore in closer proximity to DD1. In contrast, disruption of the negative Wnt signaling regulator PRY-1/Axin results in the posterior displacement of DD1 such that it is in closer proximity to DD2. To begin to understand the roles of BAR-1 and PRY-1, we examined where endogenously-tagged proteins were expressed during VNC assembly. Using CRISPR/Cas9, we generated bar-1(zy97[GFP::bar-1]) and found that BAR-1 is expressed in right but not left side-derived VNC neuroblasts. In contrast, PRY-1::mNG (cp383) is expressed in left but not right side-derived neuroblasts. In pry-1 mutants, BAR-1 is expressed symmetrically in right and left neuroblasts indicating a left-sided repression of BAR-1 signaling. We are examining how neuroblasts intercalate into a single VNC tract in bar-1 and pry-1 mutants to understand the role of this asymmetric expression. Preliminary observations suggest that motor neuron positioning defects begin to manifest around the 1.5-fold stage and later. We hypothesize that BAR-1 asymmetry in right side neuroblasts may help contribute to the proper ordering of DD, DA and DB neurons along the VNC. [1] Shah et al. Dev Cell 2017.

Lakshmi Natarajan et al. (2003) International Worm Meeting "Identifying cis-acting elements involved in the regulation of bar-1 expression"

Lakshmi Natarajan, David Eisenmann, Elizabeth Szyleyko

[International Worm Meeting, 2003]

bar-1was identified in a screen for mutants affecting vulval development. In bar-1mutants, the Vulval Precursor Cells (VPCs) adopt fused fates more often than seen in wild-type animals, Q neuroblast descendants migrate incorrectly, P12.p cell fate is misspecified and the animals are slightly uncoordinated. bar-1 encodes a C. elegans homolog of -catenin/Armadillo proteins that have two functions: cell adhesion and Wnt signaling. We know from work in our lab and others that bar-1functions through a Wnt signaling pathway in the VPCs.To determine factors that act in a cell type specific manner to regulate expression of bar-1in specific cells, we sought to isolate cis-acting elements required for bar-1expression in specific cells. We used a series of bar-1promoter deletions made as transcriptional GFP fusions to determine the spatio-temporal expression patterns in the vulva and other places. Using the above analysis, we found a 1.1kb piece of the bar-1 promoter that is sufficient to drive bar-1 expression in the VPCs, and another 1.1kb piece that is sufficient to drive expression in the Ventral Cord Neurons(VCNs). We analyzed smaller deletions within these 1.1kb regions to find minimal enhancer elements required for expression in the VPCs and the VCNs. We have narrowed down the VCN element to a 0.5kb region that is sufficient to drive expression in the VCNs. However, we could not identify a smaller VPC element that was sufficient to drive expression in the VPCs. So, we set out to identify elements within the 1.1kb VPC element that are necessary but not sufficient for expression in the VPCs. We took a bioinformatics approach and compared the sequences of the 1.1kb element found in C. elegans with that of C. briggsae to identify regions that are conserved between the two species. The two elements showed a 60% overall conservation in sequence along with some regions of tightly conserved stretches. We identified eight conserved stretches of sequences that were more than 8bp in length and scrambled each sequence individually to determine if they were important for bar-1 expression in the vulva. Results indicate that out of eight scrambled sequences analyzed, seven of them fail to show GFP expression in the vulva. This suggests that several elements within the 1.1kb VPC element appear necessary for bar-1 expression in the vulva. We are at present expressing bar-1 cDNA under the control of the 1.1kb VPC element to determine if it can rescue bar-1 mutants.

Lakshmi Natarajan et al. (2001) International C. elegans Meeting "The three C. elegans beta-catenin homologs make distinct protein interactions but retain functional redundancy in vivo"

Lakshmi Natarajan, Nina E Witwer, David M Eisenmann

[International C. elegans Meeting, 2001]

bar-1 encodes a C. elegans homolog of the b -catenin/Armadillo family of proteins which are known to function in cell adhesion and Wnt signaling. C. elegans has three b -catenin family members (BAR-1, WRM-1 and HMP-2), while Drosophila has only a single homolog which performs both functions. Interestingly, the homologs in C. elegans show only about 17-28% amino acid identity to vertebrate b -catenins and to each other. We are interested in determining if the three highly diverged b -catenin family members in C. elegans have segregated b -catenins function amongst themselves or if all three can perform both functions as in Drosophila and vertebrates. Using a directed yeast two hybrid assay, we determined if the b -catenin homologs in C. elegans have similar or different interacting factors. Results show that BAR-1 interacts with POP-1 (TCF homolog) and APR-1 (APC homolog) and not with HMP-2 ( a -catenin), suggesting a Wnt signaling function and not a cell adhesion function for BAR-1. WRM-1 however interacts with LIT-1 and POP-1, consistent with both POP-1 and LIT-1 functioning in Wnt signaling in embryogenesis. Finally, HMP-2 interacts only with vertebrate and C. elegans a -catenin (HMP-1) implying a cell adhesion function for HMP-2. Similar results have been reported by Korswagen et al .(1). These results support the idea that the three b -catenin homologs may have evolutionarily diverged from an ancestral b -catenin to perform different functions. However, wrm-1, hmp-2 and armadillo driven by the bar-1 promoter can rescue the bar-1 vulval phenotype and can thus substitute for BAR-1 function in vivo . This suggests that the homologs may still share conserved functions. However, HMP-2 can rescue only when injected at high concentrations. This suggests that high levels of the protein may result in forced interactions between HMP-2 and BAR-1 interacting factors allowing HMP-2 to substitute for BAR-1 function. We also found that BAR-1, WRM-1 and HMP-2 can all activate transcription in yeast, a function attributed to a role in Wnt signaling indicating they all share this function of b -catenin. Further characterization of BAR-1 shows that the N- and C-terminal domains possess transcriptional activation function and are required for BAR-1 activity in vivo. We have isolated BAR-1 interacting proteins (BIPs) from a yeast two hybrid screen and are testing them for their function in the vulva by RNAi. We will test these BIPs for interaction in yeast with HMP-2 and WRM-1 to determine which are common interacting factors and which are specific to BAR-1. (1) Korswagen et al. Nature 406, 527-32 (3rd Aug 2000)

Natarajan L et al. (2000) Worm Breeder's Gazette "Functional divergence of beta-catenins in C. elegans"

Witwer NE, Eisenmann DM, Natarajan L

[Worm Breeder's Gazette, 2000]

Vulval development in C. elegans is an excellent model system to study cell signaling in development. In a screen for mutants defective in vulval formation, bar-1 was identified. bar-1 was cloned and found to encode a C. elegans homolog of the b-catenin/ Armadillo family of proteins. b-catenin proteins function in two different processes; Wnt signaling and cell adhesion. Vertebrates have two b-catenin family members, b-catenin and plakoglobin, and Drosophila has one, Armadillo. In contrast, C.elegans has three members of this family (BAR-1, WRM-1 and HMP-2), of which WRM-1 functions in Wnt signaling in the embryo, BAR-1 functions in Wnt signaling in larval life and HMP-2 plays a role in cellular morphogenesis during embryogenesis. Interestingly, the three b-catenin homologs in C. elegans show only about 17-28% amino acid identity to vertebrate b-catenins and to each other, while homologs from other species show between 50-70% identity with vertebrate b-catenins. The question that follows is why does the worm have three highly divergedb-catenin family members? Are they diverged to perform different functions or are their Wnt signaling and adhesion functions still conserved? We addressed this question by taking two approaches. First, we performed a directed yeast two hybrid assay using four b-catenin proteins (BAR-1, HMP-2, WRM-1 and mouse b-catenin) fused to the Gal4 activation domain. We then tested these fusions for interactions in yeast with several proteins each fused to the Gal4 DNA Binding domain. These proteins were Wnt signaling factors POP-1, APR-1 and LIT-1, the alpha catenin homolog HMP-1 and the histone deacetylase EGL-27. Our results show that BAR-1 interacts strongly with POP-1 (TCF homolog) and APR-1 (APC homolog) and does not interact with LIT-1, EGL-27 and HMP-1. This suggests that BAR-1 may have a Wnt signaling function and not a cell adhesion function. Consistent with the results that BAR-1 interacts with APR-1 and POP-1, work from Alex Hajnal's lab has shown that apr-1 antisense RNA results in bar-1-like defects in vulval development and our lab has found that pop-1 RNAi on larvae results in a vulval phenotype, suggesting both factors act in this process with BAR-1. WRM-1 on the other hand interacts less strongly with POP-1 and is the only b-catenin tested which interacts with LIT-1. This is consistent with the fact that both POP-1 and LIT-1 are involved in WRM-1 signaling in embryogenesis. However, we did not see an interaction with WRM-1 and APR-1 even though APR-1 functions in embryonic Wnt signaling. Finally, HMP-2 does not interact with any of the Wnt signaling components but strongly interacts with vertebrate and C. elegans a-catenin (HMP-1). These results suggest that HMP-2 may have evolutionarily diverged from an ancestral b-catenin perform different functions. Similar results have recently been reported by Korswagen et al. (1) The vertebrate b-catenin tested in our assay interacts with vertebrate a-catenin, but does not interact with any of the C. elegans proteins. As another approach to understanding if the threeb-catenins have been conserved in function despite sequence divergence, we are determining if WRM-1 and HMP-2 can substitute for BAR-1 function during vulval development. wrm-1 and hmp-2 driven by the bar-1 promoter have been injected into bar-1 mutant animals and are being analyzed for rescue of the bar-1 vulval phenotype. Preliminary results show that wrm-1 is able to rescue the bar-1 mutant phenotype in the vulva suggesting that wrm-1 and bar-1 might have similar functions but different expression patterns. Taken together, our evidence suggests that C. elegans may have oneb-catenin which functions in cell morphogenesis (HMP-2) and two which function in Wnt signaling (BAR-1 and WRM-1). Therefore, the three C. elegans b-catenins may be less conserved in sequence because they have been free to diverge due to this segregation of function. (1) Korswagen et al. Nature 406, 527-32 (3rd Aug 2000)

Javier E. Irazoqui et al. (2007) International Worm Meeting "BAR-1/b-catenin and EGL-5/AbdominalB control innate immunity in C. elegans."

Emily R. Troemel, Frederick M. Ausubel, Ramnik Xavier, Javier E. Irazoqui

[International Worm Meeting, 2007]

Due to its relatively simple body plan, excellent genetic resources, and ease of propagation, Caenorhabditis elegans is an excellent model system for the study of host-pathogen interactions. We are interested in identifying signaling pathways involved in the recognition of, and response to, infection by bacterial pathogens. Using a candidate gene approach, we discovered that bar-1 mutants have an Esp (enhanced susceptibility to pathogens) phenotype when infected with either Staphylococcus aureus or Pseudomonas aeruginosa. BAR-1 codes for a homolog of <font face=symbol>b</font>-catenin, a transcription cofactor involved in the highly conserved Wnt signaling pathway. BAR-1 transcriptional activity appeared to be required for wild-type survival on pathogens, since mutation of EGL-5, a homeobox transcription factor downstream of BAR-1, also caused an Esp phenotype. In contrast, mutation of DAF-16, which interacts directly with BAR-1, caused no immunity phenotype, suggesting that BAR-1 acts in a DAF-16-independent mechanism in immunity. This is interesting given the importance of DAF-16 as a regulator of lifespan and stress responses to environmental insults. In order to better understand the role of BAR-1 and EGL-5 during infection with S. aureus, we performed microarray and qRT-PCR analysis to define a minimal set of genes whose expression is induced, mostly in the intestine, upon infection. In the majority of cases examined, induction of target genes was reduced or abolished by mutation of BAR-1. Interestingly, in egl-5 mutants this induction was reduced or abolished only for a subset of the BAR-1 target genes, consistent with EGL-5s role downstream of BAR-1, and suggesting the existence of parallel EGL-5-independent pathway(s). Similarly, BAR-1 and EGL-5 are required for full induction of a subset of P. aeruginosa-inducible genes, indicating that their role is fundamental to the response to infection by Gram-positive and -negative pathogens. This role appears to be parallel to the SEK-1/NSY-1/PMK-1 (p38 MAPK) and DAF-2/DAF-16 (insulin/IGF1) pathways that also regulate innate immunity in C. elegans, as shown by western blot analysis of PMK-1 activation and epistasis analysis. Importantly, this pathway may be conserved in mammals, since overexpression of an EGL-5 homolog leads to the induction of an NF-<font face=symbol>k</font>B reporter construct in tissue culture. Thus, we have identified a novel pathway important for host-pathogen interactions in C. elegans and, perhaps, mammals. These results suggest a role for <font face=symbol>b</font>-catenin signaling in the maintenance of intestinal homeostasis at the level of host-pathogen interactions.

Eisenmann DM et al. (2000) East Coast Worm Meeting "Characterization of the pvl-2/mig-14/mom-3 locus, which functions in multiple Wnt signaling processes in C. elegans"

Eisenmann DM, Gleason JE

[East Coast Worm Meeting, 2000]

During early larval life, P3.p P8.p express the Hox gene lin-39 and become the vulval precursor cells (VPCs). Later, the VPCs adopt one of three cell fates (1, 2, 3) in response to activation of Ras and Notch signaling pathways. This is true in 50% of animals; in the remaining 50% P3.p loses its VPC identity and fuses with the hypodermis without dividing (the Fused or F fate). Mutations in bar-1 were found in a screen for mutants with a Protruding Vulva (Pvl) phenotype. In bar-1 mutants P4.p P8.p can also adopt the F fate and lose their VPC identity, and VPCs that maintain their identity can adopt incorrect cell fates (3 instead of 1 or 2). bar-1 encodes a b-catenin/Armadillo-related protein, one of three in C. elegans. These proteins function in Wnt signaling pathways as transcription factors whose stability is regulated by Wnt signals. In bar-1 mutants, VPCs that adopt the F fate have lost lin-39 expression, indicating bar-1 is required for lin-39 regulation. This phenotype is enhanced by a mutation in let-23, indicating that the Ras and Wnt pathways coordinately regulate lin-39. bar-1 mutants also have defects in the migration of the progeny of the neuroblast QL, and in fate determination by P12. In both of these cases bar-1 appears to function in a Wnt pathway regulating Hox gene expression. Several other loci identified in the Pvl screen cause vulval defects like bar-1. One of these is pvl-2, which causes defects in VPC fate specification, QL migration and P12 fate specification, suggesting pvl-2 may function in Wnt signaling with bar-1. Consistent with this, we found that the pvl-2 F fate phenotype is also enhanced by loss of Ras signaling. pvl-2 maps to LG IIR, and fails to complement mig-14, identified by the Kenyon lab in a screen for QL migration mutants, and fails to complement mom-3, identified by Bruce Bowerman in a screen for mutants affecting mesoderm/endoderm specification. Both of these processes are known to function via Wnt signaling. Efforts to map and clone pvl-2/mig-14/mom-3 are underway. There are no know Wnt pathway components or regulators in the interval where this locus lies, suggesting it may encode a novel Wnt pathway component in C. elegans.