PROOPIOMELANOCORTIN GENE-EXPRESSION DURING PIG PITUITARY AND BRAIN-DEVELOPMENT

The expression of proopiomelanocortin (POMC) mRNA, which plays an impo rtant role in neural, endocrine, neuroendocrine and immune systems, wa s studied by in situ hybridization during the development of pituitary in the domestic pig. The POMC gene was activated as early as fetal da y 30 (E30). The signal for POMC mRNA in the anterior lobe progressivel y increased from E30 to E80 and then remained at relatively constant l evel. In contrast, POMC transcripts in the intermediate lobe first app eared at E40 and steadily increased during development. POMC transcrip ts in the brain were first found at E40 and were scattered in the arcu ate nucleus (AN) and nucleus medialis thalami (NMT). At E50 the extra- pituitary POMC mRNA was located not only in the AN and NMT but also in the fasciulus tegmenti and entorhinal cortex. In the posterior lobe, no signal was detected. The specific pattern of expression of the pig POMC gene in the pituitary and in specific regions of the central nerv ous system suggests important roles for POMC in fetal development. The se results also suggest that POMC is excellent for studying the expres sion and regulation of pituitary hormone genes because of its tissue-s pecific regulation and developmental pattern.