| Research Abstract |
We have carried out a systematic screening of peptide signaling molecules which are involved in development of fresh water coelenterate, Hydra. During the course of the screening, we have purified over 300 peptides, attempted sequencing of more than 120 peptides. Among them we have identified various interesting molecules. For example, two morphogenetic epitheliopeptides, Hym-323 and Hym-346 alter the positional values along the body axis, when exogenously applied to the animals, and enhance foot formation. The gene encoding Hym-346 is expressed in the foot region and also at the base of tentacles. During foot regeneration, its transcription begins early at the tip and continues thereafter. This suggests that the peptide is required for both foot formation and the maintenance of the foot. In contrast, the Hym-323 gene is expressed during foot formation but ceases to express when the complete foot is formed. Thus, Hym-323 appears to be required only for foot formation but not for the maintenance. Another newly found epitheliopeptide, Hym-301 is 14 amino acids long with an internal S-S bond and amidation at the C-terminus. The expression analysis of the Hym-301 gene suggested its involvement in tentacle formation. In fact, the exogenous addition of the peptide enhances tentacle formation, while the blockage of the transcrition of the Hym-301 gene with RNAi inhibits tentacle formation. These observations indicate that the peptide is involved in the tentacle formation in vivo.
In addition to epiteliopeptides, we have also identified novel neuropeptides which are involved in neuron differentiation and muscle contraction. Hym-355 is strongly expressed in the head and foot neurons and appears to be a feedback signal to regulate neuron density together with PW peptides, a family of epitheliopeptides.
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