Theska, Tobias et al. (2021) International Worm Meeting "NHR-1 and NHR-40 in C. elegans - an outgroup approach to the origin of a novel trait"

Theska, Tobias, Sommer, Ralf

[International Worm Meeting, 2021]

A longstanding prediction of evolutionary theory is that phenotypic plasticity, the ability of one genotype to produce different phenotypes based on environmental input during development, plays a significant role in the evolution of morphological novelty. Nematodes of the Diplogastridae family are characterized by the presence of such a novelty: they possess cuticular teeth at the base of their mouths. Additionally, these structures are also polyphenic; different environmental cues can induce development of either a predatory form with two large teeth or a bacterivorous morph with only one dorsal tooth. Previous work demonstrated that two nuclear receptors, Ppa-NHR-1 and Ppa-NHR-40, regulate the morphogenesis of these teeth in Pristionchus pacificus. Interestingly, nematodes outside of the Diplogastridae, like Caenorhabditis elegans, lack this morphological novelty and the associated phenotypic plasticity entirely. Instead, these worms are monomorphic with simple, triangular flaps at the base of their mouths. However, Ppa-nhr-1 and Ppa-nhr-40 are the only genes of the P. pacificus mouth-form regulatory network that retain 1:1 orthologs in C. elegans. Therefore, we investigate whether these transcription factors also have a conserved function in regulating the development of the C. elegans mouth. Using the CRISPR/Cas9 system, we generated small indels in the coding sequences of Cel-nhr-1 and Cel-nhr-40 and isolated frameshift mutants to ensure a loss-of-function. Additionally, we aim to investigate the localization of both nuclear receptors by tagging them with fluorescent protein markers (e.g., mNeonGreen). In order to identify potential mutant phenotypes, we quantify differences in mouth shape between wildtype and CRISPR-edited strains by applying landmark-based geometric morphometrics in combination with k-medoid and model-based clustering.This data will be complemented with future RNA-seq experiments, which will identify the regulatory targets of Cel-NHR-1 and Cel-NHR-40. Taken together, this data will allow a comparison of the cellular localization, the regulatory targets, and the functional relevance of NHR-1 and NHR-40 for stoma development between C. elegans and P. pacificus. Ultimately, this study will reveal whether these nuclear receptors share a conserved function in stoma development that predates the evolution of the morphological novelty, or if a neo-functionalization accompanied its origin.

Schramp, Mark W. et al. (2011) International Worm Meeting "TES-1 mediates epithelial morphogenesis."

Schramp, Mark W., Lynch, Allison, Hardin, Jeff

[International Worm Meeting, 2011]

tes-1 encodes an ortholog of human Testin. TES has been identified as a tumor suppressor(Tobias et al., 2001) and a novel focal adhesion-associated protein that can co-localize with paxillin and zyxin, which it depends on for focal adhesion targeting in mouse fibroblast cells(Garvalov et al., 2003). In addition, TES has been shown to enhance cell spreading and inhibit cell migration, highlighting its potential role as a tumor suppressor. Recently, TES was shown to co-localize with -catenin at sites of cell-cell contact in fibroblasts(Griffith et al., 2004), corroborating its potential role as a modulator of cell attachments. tes-1 was identified in a screen for enhancers of embryonic lethality observed in worms homozygous for a hypomorphic allele (fe4) of hmp-1/-catenin. The fe4 mutation results in ~70% embryonic lethality, with most embryos showing elongation defects and varying degrees of defects in circumferential F-actin bundles (CFBs). The knockdown of tes-1 by feeding RNAi in fe4 worms results in >98% embryonic lethality with the vast majority of embryos exhibiting the Humpback phenotype characterized by dorsal humps along the body axis. Using a TES-1::GFP fusion protein driven by the tes-1 promoter, we have found that tes-1 is expressed in the hypodermis and in neurons during embryogenesis. During the process of embryonic elongation, TES-1 expressed in seam hypodermal cells localizes with HMR-1 at sites of cell-cell contact, just apical to the DLG-1/AJM-1 complex. In adult hermaphrodites, TES-1 is expressed in many neurons including the nerve ring, ventral nerve cord and tail ganglia. In addition, TES-1 is expressed in epithelial cells of the vulva and uterus. Worms homozygous for a tes-1 null allele (ok1036) do not exhibit increased embryonic lethality