Expression of pro-opiomelanocortin (POMC) in the cerebral ganglion and ovary of a protochordate.

The distribution of neurones expressing POMC mRNA in the cerebral ganglion of the protochordate ascidian, Styela plicata, was investigated using a non-radioactive in situ hybridization technique. Nerve cell bodies of mono and bipolar types expressing POMC mRNA, were observed mainly in the outer layer of the ganglion. Discrete groups of neurones containing POMC mRNA were also localized in the inner portion of the ganglion, and few small monopolar perykaria expressing POMC mRNA were visible at the emergence of the main nerve trunks. POMC mRNA labeling was also found at level of the cytoplasm of previtellogenic and vitellogenic oocytes, and of follicular cells. Our results demonstrate the expression of one or more genes in the cerebral ganglion and ovary, that may be similar to one or more regions of the mammalian POMC gene. Therefore POMC-related molecules seem to be involved in neuromodulatory pathways and regulatory mechanisms of the oogenesis of ascidians.