The head activator was first isolated from the sea anemone Anthopleura elegantissima.An identical peptide was also purified and identified in Hydra magnipapillata as well as in the hypothalamus and intestine of rats and humans.
Distribution of the head activator The head activator has been identified in Hydra as well as in the hypothalamus and intestine of rats and humans, where the peptide appears to have a role in neuronal differentiation.It has been suggested that the head activator acts as a neuropeptide,although direct evidence is lacking. Recently, the Hydra Genome Project was completed; however, the Hydra genome sequence does not include a putative head activator gene, and therefore the nature of this factor is uncertain.
The head activator andthe head inhibitor.When a certain threshold ratio of head activator to head inhibitor is attained, a head forms. The head activator increases the rate of head regeneration and bud formation, and increases the number of regenerated tentacles. Thus, this peptide was initially characterized as a morphogen. The head activator also functions as a mitogen and an inducer of neuronal differentiation.
The head activator is a neuropeptide that regulates pattern-forming processes in Hydra magnipapillata.
