The C elegans hunchback homolog, hbl-1, controls temporal patterning and is a probable microRNA target.

Abstract hunchback regulates the temporal identity of neuroblasts in Drosophila. Here we show that hbl-1 , the C. elegans hunchback ortholog, also controls temporal patterning. Furthermore, hbl-1 is a probable target of microRNA regulation through its 3′UTR. hbl-1 loss-of-function causes the precocious expression of adult seam cell fates. This phenotype is similar to loss-of-function of lin-41 , a known target of the let-7 microRNA. Like lin-41 mutations, hbl-1 loss-of-function partially suppresses a let-7 mutation. The hbl-1 3′UTR is both necessary and sufficient to downregulate a reporter gene during development, and the let-7 and lin-4 microRNAs are both required for HBL-1/GFP downregulation. Multiple elements in the hbl-1 3′UTR show complementarity to regulatory microRNAs, suggesting that microRNAs directly control hbl-1 . MicroRNAs may likewise function to regulate Drosophila hunchback during temporal patterning of the nervous system.