The tailless ortholog nhr-67 functions in the development of the C. elegans ventral uterus

The development of the C. elegans uterus provides a model for understanding the regulatory pathways that control organogenesis. In C. elegans, the ventral uterus develops through coordinated signaling between the uterine anchor cell (AC) and a ventral uterine (VU) cell. The nhr-67 gene encodes the nematode ortholog of the tailless nuclear receptor gene. Fly and vertebrate tailless genes function in neuronal and ectodermal developmental pathways. We show that nhr-67 functions in multiple steps in the development of the C. elegans uterus. First, it functions in the differentiation of the AC. Second, it functions in reciprocal signaling between the AC and an equipotent VU cell. Third, it is required for a later signaling event between the AC and VU descendants. nhr-67 is required for the expression of both the lag-2/Delta signal in the AC and the lin-12/Notch receptor in all three VU cells and their descendants, suggesting that nhr-67 may be a key regulator of Notch-signaling components. We discuss the implications of these findings for proposed developmental regulatory pathways that include the helix-loop-helix regulator hlh-2/daughterless and transcription factor egl-43/Evi1 in the differentiation of ventral uterine cell types.