Using C. intestinalis to study Islet in ascidian palp morphogenesis

In Ciona intestinalis, the palps consist of three conical protrusions within a field of thickened epithelium that form late in embryogenesis as tailbuds mature into larvae. The palp protrusions express the LIM-homeodomain transcription factor Islet. Protrusion occurs through differential cell elongation, likely mediated by Islet, as we find that ectopic expression of Islet is sufficient to promote cell elongation. FGF signaling is required for both Islet expression and palp morphogenesis. Importantly, we show that Islet expression can rescue the palp-deficient phenotype that results from inhibition of FGF signaling. We conclude that Islet is a key regulatory factor governing morphogenesis of the palps. It is conceivable that Islet is also essential for the cellular morphogenesis of placode-derived sensory neurons in vertebrates. Islet expression can rescue the palp-deficient phenotype that results from inhibition of FGF signaling, and conclude that Islet is a key regulatory factor governing morphogenesis of the palps. Three biological replicates were analyzed for both sample types (Fox positive and Negative).