ACaenorhabditis elegansHomologue ofhunchbackIs Required for Late Stages of Development but Not Early Embryonic Patterning

AbstractWe have cloned aCaenorhabditis eleganshomologue of theDrosophilagap genehunchback(hb) and have designated ithbl-1(hunchback-like).hbl-1encodes a predicted 982-amino-acid protein, containing two putative zinc-finger domains similar to those ofDrosophilaHunchback. The gene is transcribed embryonically, but unlike the maternally expressedDrosophila hb,its mRNA is not detected inC. elegansoocytes. Ahbl-1::gfpreporter is expressed primarily in ectodermal cells during embryonic and larval development. Double-stranded RNA-interference (RNAi) was used to indicatehbl-1loss-of-function phenotypes. Progeny ofhbl-1(RNAi)hermaphrodites exhibit a range of defects; the most severely affected progeny arrest as partially elongated embryos or as hatching, misshapen L1 larvae. Animals that survive to adulthood exhibit variably dumpy (Dpy), uncoordinated (Unc), and egg-laying defective (Egl) phenotypes, as well as defects in vulval morphology (Pvl). Abnormal organization of hypodermal cells and expression of a hypodermal marker inhbl-1(RNAi)animals suggests that most of the phenotypes observed could be due to improper specification of hypodermal cells. The pattern ofhbl-1expression is similar to that reported for the leech hunchback homologueLzf-2,suggesting that these proteins may have similar biological functions in diverse species with cellular embryos