Meeting Abstract
The class I POU-domain transcription factor, POU-I (Pit-1), has an ancient evolutionary origin at the base of animals, but was later lost in protostome bilaterian lineages (e.g. Drosophila and C. elegans). Pit-1 plays an essential role in the development of the vertebrate anterior pituitary gland by regulating differentiation of peptide-hormone-producing cell types, but its ancestral function basal to vertebrates is poorly understood. In amphioxus, Pit-1 is expressed in the pre-oral organ which is believed to be a chemosensory and neurosecretory organ homologous to the adenohypophysis, and in the scyphozoan cnidarian, Aurelia sp.1, Pit-1 is expressed in a subset of sensory cells in the ectoderm of rhopalia (sensory organs). These comparative gene expression data raise the possibility that Pit-1 directed differentiation of sensory cells in the last common ancestor of Cnidaria and Bilateria. To further examine this hypothesis, we are analyzing the developmental expression pattern and function of Pit-1 in the anthozoan cnidarian Nematostella vectensis, by using in-situ hybridization, immunohistochemistry and CRISPR-Cas9-mediated targeted mutagenesis. We find that during the planula stage Pit-1 is expressed throughout the endoderm, and, at tentacle-bud and polyp stages its expression becomes restricted to ectodermal sensory cells in the tentacles. These data are consistent with Pit-1 having a role in differentiation of sensory cell types. We are currently characterizing the subpopulations of Pit-1 positive cells and generating knockout animals to test whether Pit-1 is necessary to regulate the differentiation of sensory cells in anthozoans. Further investigation is required to clarify if Pit-1+ cells of Nematostella vectensis produce growth-related hormones and neuropeptides as seen in chordates.
