Jelly belly, a novel signal and its receptor. J.B. Weiss 1, H. Lee 2, A. Norris 1, M. Frasch 2. 1) Molecular Medicine, OHSU, Portland, OR; 2) Cell and Developmental Biology Mount Sinai School of Medicine.
The signaling protein Jelly belly (Jeb) was identified as a transcriptional target of the homeodomain protein Tinman. Jeb is made in somatic muscle precursors, secreted and taken up by visceral mesoderm precursors. Mutants that lack functional Jeb have no mature smooth muscle. Jeb is not required for visceral mesoderm specification but does provide essential positional information to circular muscles of the gut. We have recently identified a tissue-specific, high-affinity signaling receptor for Jeb. The Jeb receptor, DAlk, binds Jeb with a Kd of approximately 2nM. It is a receptor-tyrosine-kinase and member of the insulin receptor superfamily. We have shown in a heterologous tissue culture system that Jeb binding is necessary and sufficient to activate the receptor as well as downstream components of the signal transduction pathway. We have also shown that dominant negative receptors phenocopy jeb mutations and that activated ras partially rescues jeb mutations.