Morphogenesis in C. elegans is a highly dynamic process in which a bean shaped embryo is transformed into its final adult form. During this process, epithelial cells extend to form sheets and tubes that shape the body and form organs. Disrupted epithelial morphogenesis often leads to embryonic arrest and defects, such as those displayed by the
vab-1 and
vab-2 mutants, which encode the ephrin and eph receptor, respectively(1,2). Here, we describe the role of the
lawd-1 (lumen associated with WD40 domain) gene in epithelial morphogenesis. The
lawd-1 mutants
cr7 and
tm4605 each display a highly penetrant viable Vab (Variable abnormal) phenotype and a less penetrant embryonic lethality. Genetic analyses indicate that neither allele is likely to be null, hence a new knockout allele is being generated using CRISPR/Cas9. Both
lawd-1 mutants are rescued by a recombineered fosmid containing
lawd-1::mCherry (C-terminal). The LAWD-1::mCh reporter is expressed throughout development in all epithelial tissues except the hypodermis. Given that
lawd-1 mutants have a Vab phenotype, the absence of hypodermal expression, except in seam cells, is surprising although this may simply be due to a lack of germline expression despite the ability of the reporter to rescue
lawd-1 mutants. We are making a germline reporter to test this possibility. When
lawd-1::mCh is co-expressed in embryos with the epithelial markers
hmp-1::gfp,
dlg-1::gfp or lifeact::gfp, we find that LAWD-1::mCh is apically enriched in epithelial cells. The
lawd-1 gene is predicted to encode multiple isoforms, a number of which have been detected by western analysis. Some of these isoforms have the potential to form an N-terminal double-propeller with 2x7 WD40 repeats. The presence of a LAWD-1 WD40 domain has led us to hypothesise that LAWD-1 mediates protein-protein interactions with other proteins involved in epithelial morphogenesis. To test this hypothesis we have co-immunoprecipitated LAWD-1::mCh and identified potential interacting partners by mass spectrometry. Several of the candidates isolated have known roles in epithelial development. One such candidate is VAB-10B, a spectraplakin isoform that interacts with actin during elongation3. Interestingly, a synthetic lethal interaction has also been detected between
lawd-1 and
sma-1, which encodes the actin interacting protein beta-H spectrin4. We are currently validating the candidate LAWD-1 interacting proteins identified in our screen.Ref. 1Chin-Sang ID et al. (1999) Cell. 99;781. 2George SE et al. (1998) Cell. 92;633. 3Bosher JM et al. (2003) J. Cell Biol. 161;757. 4McKeown C et al. (1998) Development. 125(11);2087.