Molecular cloning of porcine neuronatin and analysis of its expression during pituitary ontogeny.

We cloned and sequenced two types (alpha and beta type) of cDNA from the porcine anterior pituitary cDNA library, encoding neuronatin that has been cloned as a gene expressed by the fetal developing brain. Nucleotide sequences of alpha and beta type were identical except for two gaps, suggesting that they were produced by an alternative splicing. The amino acid sequences showed a high homology (more than 94 %) compared to those of other mammals, including human, rat, and mouse. In this study, RT-PCR was performed for the RNA samples prepared from the porcine fetal and postnatal pituitaries. The results showed that two types of neuronatin are expressed through the fetal stages, from day 40 to day 110 in both sexes. The relative amounts of alpha to beta type reversed just after birth in both sexes, and both amounts increased further in the postnatal anterior pituitary. This increased expression after birth is quite different from the brain in which the expression of neuronatins decreased, indicating the distinct role of the neuronatin in pituitary and brain. Finally, we found a pituitary cell type specific localization, especially in gonadotroph cell lines LbetaT2, of beta-neuronatins.