Our analysis of 86 genes on chromosome I by feeding versus injection identified 13 with an RNAi phenotype. Among these 13 genes were two, apr-1 and mei-1, previously reported to have loss-of-function phenotypes. apr-1 encodes a protein similar to the APC (adenomatous polyposis coli) protein; it is involved in Wnt signaling and has previously been shown to control endoderm induction in the embryo [22]. Although we failed to obtain embryonic lethality for apr-1 by feeding, we did identify reproducible and specific phenotypes - uncoordinated movement, body morphology defects, and larval lethality - consistent with the expression pattern and previously demonstrated roles for this gene [23]. Both feeding and injection produced strong embryonic lethality for mei-1, a regulator of meiosis [12]. Furthermore, by titrating the IPTG concentration, we were able to phenocopy the Him phenotype of a weak mei-1 mutant, which is indicative of X-chromosomal non-disjunction during meiosis [13].
