Abstract
Recently, we discovered a novel cDNA encoding the precursor of a small secretory protein, neurosecretory protein GL (NPGL), in the hypothalamic infundibulum of chickens. NPGL plays an important role in the regulation of growth and feeding. A database search indicated that the NPGL gene has a paralogous gene: neurosecretory protein GM (NPGM), also in chickens. We identified cDNA encoding the NPGM precursor in chickens. Morphological analysis showed that NPGM-containing cells are specifically localized in the medial mammillary nucleus (MM) and infundibular nucleus (IN) in the hypothalamus. In addition, we found that NPGM and NPGL are co-localized, especially in the MM. The expression levels of NPGM mRNA gradually decreased during post-hatch development, in contrast to those of NPGL mRNA. Moreover, we investigated the relationship between NPGM and other known factors. NPGM was found to be produced in histaminergic neurons in the MM. NPGM and histidine decarboxylase, a histamine-producing enzyme, displayed similar expression patterns during post-hatch development. Acute intracerebroventricular injection of NPGM decreased food intake, similar to the effect of histamine. To our knowledge, this is the first report of the localization and function of NPGM in the brain of vertebrates. These results will further advance the understanding mechanisms underlying energy homeostasis.
Highlights
We discovered a novel cDNA encoding the precursor of a small secretory protein, neurosecretory protein GL (NPGL), in the hypothalamic infundibulum of chickens
We found that neurosecretory protein GM (NPGM)-immunoreactive cells were localized in the mammillary nucleus (MM) and the infundibular nucleus (IN) (Fig. 6a,c and e), but that the precursor mRNA for histidine decarboxylase (HDC), a histamine-producing enzyme, was only expressed in the MM (Fig. 6b,d and f)
The NPGM precursor mRNA and protein were expressed in the MM and the IN in the hypothalamic infundibulum
Summary
We discovered a novel cDNA encoding the precursor of a small secretory protein, neurosecretory protein GL (NPGL), in the hypothalamic infundibulum of chickens. Acute intracerebroventricular injection of NPGM decreased food intake, similar to the effect of histamine To our knowledge, this is the first report of the localization and function of NPGM in the brain of vertebrates. Avian and mammalian species share many common neuropeptides which maintain energy homeostasis, such as NPY, POMC, CRH, melanin-concentrating hormone (MCH), and ghrelin[10]. These peptides do not always play similar roles in birds and mammals[10]. We identified a novel cDNA encoding the precursor of a small neurosecretory protein in the hypothalamus of chickens, mice, and rats[14,15,16]. To investigate the physiological function(s) of NPGM and the relationship between NPGM and NPGL, we performed cDNA cloning of the NPGM precursor and analyzed its localization and the effects of i.c.v. injection of mature NPGM in chicks
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