To help identify genes important in intestinal morphogenesis we are attempting to construct an intestine-specific RNAi system. We are expressing
rde-1(+)under control of an intestinal promoter,
end-1, in
rde-1 mutant embryos (referred to as
end-1::RDE-1 embryos). We have tested our system by performing RNAi against
hmr-1, a classical cadherin expressed in all epithelia in C. elegans (Costa et al., 1999). Based on expression of
end-1::GFP reporter constructs, we would have expected penetrant RNAi effects at early stages of embryogenesis; however, we only see significant loss of HMR-1 staining in the intestine of late embryos, approximately two-fold and pretzels.
hmr-1(RNAi) in
end-1::RDE-1 embryos, either by injection or bacterially-mediated delivery, produces no lethality in embryos, in contrast to N2 embryos, which die with major defects in body morphogenesis and enclosure. In some of the treated
end-1::RDE-1 embryos, we have observed partial loss of HMR-1 staining in hypodermal cells with concomitant hypodermal morphogenesis defects; this may be due to the fact that the
rde-1 allele we used,
ne219, is not a null. We have also attempted to inhibit the function of two other genes reported to be required for intestinal morphogenesis,
die-1 (Heid et al., 2001) and
lin-12(Hermann et al., 2000) using our system, and failed to observe the expected phenotypic defects. Hmr-1,
die-1, and
lin-12 are expressed both maternally and zygotically, so it is possible that perdurance of maternal product may interfere with our ability to inhibit gene function.