Shea C et al. (1995) International C. elegans Meeting "SEARCH FOR ECR HOMOLOGS IN NEMATODES"

Maina CV, Hough DM, Shea C, Richer J

[International C. elegans Meeting, 1995]

Dirofilaria immitis, the causative agent of dog heartworm disease, is a model system for the study of filarial parasites. Filariasis afflicts over 300 million people worldwide, causing serious and debilitating disease. Knowledge of the molecular mechanisms involved in parasite development will facilitate the design of therapeutic agents. Nematodes such as D. immitis undergo a series of larval molts before becoming sexually mature adults. The steroid hormone ecdysone is present in D. immitis and is capable of stimulating molting in the parasite in vitro. This suggests that ecdysone has a role in regulating molting and possibly other developmental processes in filaria. In order to understand these processes, we have identified a D. immitis ecdysone receptor (EcR) homolog, dinhr-3, by PCR using degenerate primers derived from the sequence of the DNA binding domain of the Drosophila EcR. The dinhr-3 cDNA, compared with the Drosophila EcR, shows 79% amino acid identity in the DNA binding domain and 59% amino acid identity over the E1, E2, and E3 regions of the hormone binding domain. In Drosophila, EcR heterodimerizes with ultraspiracle (Usp), an RXR family member. A putative Usp homolog from D. immitis, dinhr-4, has also been identified showing 81% identity in the DNA binding domain and 52% over the E1, E2, and E3 regions of the hormone binding domain. The biochemistry and developmental regulation of these NHR's are being investigated. In addition we have isolated several other NHR's from D. immitis and C. elegans some showing significant sequence similarity with specific members of the NHR superfamily (see abstract by Sluder et. al.). Further molecular characterization of dinhr-3, dinhr-4,and the other NHR's is currently underway. Identifying genes which are regulated by the EcR and exploring their roles in parasite development will allow the development of strategies to combat filariasis.

Zhang T et al. (2021) Food Funct "Differentiated 4,4-dimethylsterols from vegetable oils reduce fat deposition depending on the NHR-49/SCD pathway in Caenorhabditis elegans."

Chang M, Zhang T, Xie L, Wang X, Jin Q, Liu R

[Food Funct, 2021]

Consumption of 4-desmethylsterols has been claimed to have many beneficial effects, but the benefits of 4,4-dimethylsterols are less appreciated. We utilized a nematode model, Caenorhabditis elegans (C. elegans), to explore the anti-obesity effects of different classes of 4,4-dimethylsterols purified from rice bran oil (RST) and shea nut butter (SST). Both SST and RST significantly reduced fat deposition in C. elegans with smaller sizes and numbers of lipid droplets. But the food intake was not significantly affected. Metabolomics analysis indicated a significantly altered pathway after treatment with 4,4-dimethylsterols. Finally, it was found that 4,4-dimethylsterols targeted stearoyl-CoA desaturases (SCD) and nuclear hormone receptor-49 (NHR-49), resulting in a reduced desaturation index as proved by a lower ratio of oleic acid (C18:1n-9) to stearic acid (C18:0). Overall, 4,4-dimethylsterols can inhibit fat deposition via regulating the NHR-49/SCD pathway in C. elegans.

Sluder AE et al. (1995) International C. elegans Meeting "NEMATODE NUCLEAR HORMONE RECEPTORS: TWO DOZEN AND COUNTING"

Maina CV, Lindblom TH, Hough DM, Sluder AE, Wong S, Robbins A

[International C. elegans Meeting, 1995]

To date 24 C. elegans genes encoding members of the nuclear hormone receptor (NHR) superfamily of transcription factors have been identified, primarily by our direct homology screens and by the genome sequencing project. Most of these genes encode widely divergent members of the NHR superfamily. While all exhibit significant sequence similarity in the highly conserved DNA-binding domain, many (13/24) have unique amino acid sequences in the region responsible for DNA binding site recognition, suggesting that the DNA binding specificities of these C. elegans proteins will differ from those of previously characterized NHRs. All of the C. elegans NHRs are "orphan" receptors for which the ligands, if any, are unknown. Though not as highly conserved as the DNA-binding domains, blocks of sequence similarity are found in the ligand-binding domains of all NHRs known to bind ligands. These regions of similarity are also seen in many, but not all, orphan receptors, including at least 10 of the C. elegans NHRs. Five NHR genes have also been identified in the dog heartworm Dirofilaria immitis. One of these, dinhr-2, is closely related to the C. elegans gene nhr-6. Two others exhibit significant homology to the two genes encoding subunits of the Drosophila ecdysone receptor (see abstract by Shea et al.). As little is known about the biological roles of most of the C. elegans NHR genes we are undertaking genetic analysis of a selected subset. Tc1 insertions have been generated in nhr-6 and in the embryonically expressed nhr-2; deletion screens are underway. Progress in these and other screens will be presented.

Julianne Paille et al. (2007) International Worm Meeting "An RXR nuclear receptor homolog from Pristionchus pacificus."

Sharita Flowers, Chris R. Gissendanner, Julianne Paille

[International Worm Meeting, 2007]

The retinoic acid X receptors (RXRs) are considered to be an ancient group of nuclear receptors and have been identified in a variety of metazoans, including nematodes. However, the presence of RXR homologs in nematodes has only been confirmed in filarial parasites (Shea et al, 2004). In insects, the RXR homolog USP interacts with the EcR nuclear receptor to function as the holoreceptor for the molting hormone 20-hydroxyecdysone. Neither RXR nor EcR nuclear receptor homologs are encoded in the C. elegans and C. briggsae genomes, even though many of the nuclear receptors that function downstream of USP/EcR in insects are found in C. elegans and function to regulate the nematode molting process (Gissendanner et al, 2004). Therefore, an interesting question is whether RXR, and EcR, are found in other, non-parasitic nematodes. A search of genome sequences from the free-living nematode Pristionchus pacificus identified a genomic fragment encoding a potential RXR nuclear receptor. This fragment was used to design RT-PCR experiments to isolate cDNAs encoding this putative RXR nuclear receptor. We have successfully isolated several full-length cDNAs corresponding to the genomic sequence, and these cDNAs encode a nuclear receptor with significant similarity to RXR nuclear receptors (>80% in the DNA binding domain). Several mRNA isoforms have been isolated. Temporal expression profiles using semi-quantitative RT-PCR indicate expression fluctuations that correlate with the molting cycle, suggesting a role for the Pristionchus pacificus RXR during molting. We are currently further testing this hypothesis using Northern analysis and RNA interference. The isolation of an RXR nuclear receptor from a free-living nematode provides an opportunity to investigate the biological functions and evolution of RXR in nematodes.

Zhao Y et al. (2007) BMC Genomics "Poly-G/poly-C tracts in the genomes of Caenorhabditis."

Zhao Y, O'Neil NJ, Rose AM

[BMC Genomics, 2007]

ABSTRACT: BACKGROUND: In the genome of Caenorhabditis elegans, homopolymeric poly-G/poly-C tracts (G/C tracts) exist at high frequency and are maintained by the activity of the DOG-1 protein. The frequency and distribution of G/C tracts in the genomes of C. elegans and the related nematode, C. briggsae were analyzed to investigate possible biological roles for G/C tracts. RESULTS: In C. elegans, G/C tracts are distributed along every chromosome in a non-random pattern. Most G/C tracts are within introns or are close to genes. Analysis of SAGE data showed that G/C tracts correlate with the levels of regional gene expression in C. elegans. G/C tracts are over-represented and dispersed across all chromosomes in another Caenorhabditis species, C. briggase. However, the positions and distribution of G/C tracts in C. briggsae differ from those in C. elegans. Furthermore, the C. briggsae dog-1 ortholog CBG19723 can rescue the mutator phenotype of C. elegans dog-1 mutants. CONCLUSIONS: The abundance and genomic distribution of G/C tracts in C. elegans, the effect of G/C tracts on regional transcription levels, and the lack of positional conservation of G/C tracts in C. briggsae suggest a role for G/C tracts in chromatin structure but not in the transcriptional regulation of specific genes.

Bhagwati P Gupta et al. (2002) West Coast Worm Meeting "Genetic analysis of the vulval mutants in C. briggsae"

Shahla Gharib, Bhagwati P Gupta, Paul W Sternberg, Jennifer X Li

[West Coast Worm Meeting, 2002]

To understand the evolution of developmental mechanisms, we are doing a comparative analysis of vulval patterning in C. elegans and C. briggsae. C. briggsae is closely related to C. elegans and has identical looking vulval morphology. However, recent studies have indicated subtle differences in the underlying mechanisms of development. The recent completion of C. briggsae genome sequence by the C. elegans Sequencing Consortium is extremely valuable in identifying the conserved genes between C. elegans and C. briggsae.

Antika TR et al. (2023) J Biol Chem "Sequence-specific targeting of C. elegans C-Ala to the D-loop of tRNAAla."

Horng JC, Hsu HL, Nazilah KR, Wang CC, Wang TL, Wang SC, Antika TR, Chuang TH, Chrestella DJ, Wang SW, Tseng YK, Pan HC

[J Biol Chem, 2023]

Alanyl-tRNA synthetase (AlaRS) retains a conserved prototype structure throughout its biology. Nevertheless, its C-terminal domain (C-Ala) is highly diverged and has been shown to play a role in either tRNA or DNA binding. Interestingly, we discovered that Caenorhabditis elegans cytoplasmic C-Ala (Ce-C-Ala_c) robustly binds both ligands. How Ce-C-Ala_c targets its cognate tRNA and whether a similar feature is conserved in its mitochondrial counterpart remain elusive. We show that the N- and C-terminal subdomains of Ce-C-Ala_c are responsible for DNA and tRNA binding, respectively. Ce-C-Ala_c specifically recognized the conserved invariant base G¹⁸ in the D-loop of tRNA^Ala through a highly conserved lysine residue, K934. Despite bearing little resemblance to other C-Ala domains, C. elegans mitochondrial C-Ala (Ce-C-Ala_m) robustly bound both tRNA^Ala and DNA and maintained targeting specificity for the D-loop of its cognate tRNA. This study uncovers the underlying mechanism of how C. elegans C-Ala specifically targets the D-loop of tRNA^Ala.

Blumenthal TE et al. (1994) Worm Breeder's Gazette "C. elegans U2AF 65."

Zorio DAR, Lea K, Blumenthal TE

[Worm Breeder's Gazette, 1994]

C. elegans U2AF65

Oomura, S. et al. (2019) International Worm Meeting "Early embryogenesis of C. inopinata, a sibling species of C.elegans."

Matsumura, Y., Haruta, N., Hoshi, Y., Sugimoto, A., Oomura, S.

[International Worm Meeting, 2019]

C. inopinata is a newly discovered sibling species of C. elegans. Despite their phylogenetic closeness, they have many differences in morphology and ecology. For example, while C. elegans is hermaphroditic, C. inopinata is gonochoristic; C. inopinata is nearly twice as long as C. elegans. A comparative analysis of C. elegans and C. inopinata enables us to study how genomic changes cause these phenotypic differences. In this study, we focused on early embryogenesis of C. inopinata. First, by the microparticle bombardment method we made a C. inopinata line that express GFP::histone in whole body, and compared the early embryogenesis with C. elegans by DIC and fluorescent live imaging. We found that the position of pronuclei and polar bodies were different between these two species. In C. elegans, the female and male pronuclei first become visible in anterior and posterior sides, respectively, then they meet at the center of embryo. On the other hand, the initial position of pronuclei were more closely located in C. inopinata. Also, the polar bodies usually appear in the anterior side of embryo in C. elegans, but they appeared at random positions in C. inopinata. Therefore, we infer that C. inopinata may have a different polarity formation mechanism from that in C. elegans. We are also analyzing temperature dependency of embryogenesis in C. inopinata, whose optimal temperature is ~7 degree higher than that in C. elegans.

Guven K (1995) Journal of Thermal Biology "Differential expression of hsp70 proteins in response to heat and cadmium in Caenorhabditis elegans."

Guven K

[Journal of Thermal Biology, 1995]

1. The patterns of HSP70 expression induced in Caenorhabditis elegans by mild (31 degrees C) or severe (34 degrees C) heat shock, and by cadmium ions at 31 degrees C, have been compared with those expressed constitutively ill 20 degrees C controls by 1- and a-dimensional immunoblotting. 2. The 2D spot patterns become more complex with increasing severity of stress (34 degrees C > 31 degrees C + Cd > 31 degrees C > 20 degrees C). 3. A stress-inducible transgene construct is minimally active at 31 degrees C, but is abundantly expressed in the presence of cadmium or at 34 degrees C. 4. Differing degrees or types of stress may differentially induce available hsp70