Reciprocal EGFR signaling in the Anchor Cell ensures precise inter-organ connection during C. elegans vulval morphogenesis

During C. elegans vulval development, the uterine anchor cell (AC) first secretes an epidermal growth factor (EGF) to specify the vulval cell fates and then invades into the underlying vulval epithelium. Thereby, the AC establishes direct contact with the invaginating 1° vulF cells and attaches the developing uterus to the vulva. The signals involved and the exact sequence of events joining these two organs are not fully understood. Using a conditional let-23 egf receptor (EGFR) allele along with novel microfluidic short- and long-term imaging methods, we discovered a specific function of the EGFR in the AC during vulval lumen morphogenesis. Tissue-specific inactivation of let-23 in the AC resulted in imprecise alignment of the AC with the 1° vulval cells, delayed AC invasion and disorganized adherens junctions at the newly forming contact site between the AC and the dorsal vulF toroid. We propose that EGFR signaling, activated by a reciprocal EGF cue from the 1° vulval cells, positions the AC at the vulval midline, guides it during invasion and assembles a cytoskeletal scaffold organizing the adherens junctions that connect the developing uterus to the dorsal vulF toroid. EGFR signaling in the AC thus ensures the precise alignment of the two developing organs.