Study on molecular mechanism of melanocyte-stimulating hormone system in the chicken

1. a-MSH在鸟类外周组织中的存在及其可能的生理作用尚未确定。结合RT-PCR、免疫细胞化学和原位杂交技术，我们鉴定了a- msh在发育中的眼内表达，并在时间和空间上受到调控。结果表明，在胚胎期和出生后，视网膜色素上皮细胞（RPE细胞）和视锥细胞分别是a-MSH的眼内来源。这是首次报道a- msh在鸟类外周组织中的表达，支持了我们关于鸟类a- msh是一种旁分泌/自分泌激素的假设。生长激素（GH）被认为在糖尿病视网膜病变的光发生中起作用。RT-PCR和5′race分析鉴定了一种新的生长激素异构体在发育中的鸡眼中表达。免疫细胞化学显示，新的生长激素异构体，被称为s-cGH，与RPE细胞中的生长激素受体的结合受到暂时调节，并与胚胎发育期间RPE细胞中a- msh的产生密切相关，这意味着s-cGH可能参与了眼部发育的调节。许多脊椎动物在禁食后所表现出的代偿性贪食的神经机制尚不完全清楚，但在哺乳动物中，似乎涉及下丘脑中共同表达神经肽Y （NPY）和针刺相关蛋白（AGRP）的营养敏感神经元。我们研究了这些神经元是否在非哺乳动物脊椎动物日本鹌鹑中进化保守。双标记原位杂交结果表明，在脊椎动物的进化过程中，大多数NPY神经元共表达AGRP mRNA，表明这种细胞类型在神经解剖学和功能上是保守的。

1. The presence and possible physiological roles of a-MSH in the peripheral tissues of birds have not established. By a combination of RT-PCR, immunocytochemitry and in situ hybridization, we identified the expression of a-MSH in the eye, which is regulated temporally and spatially in the developing chicken. The data clearly indicated that the retinal pigment epithelial cells (RPE cells) and the cone cells are intraocular sources of a-MSH in the embryonic and postnatal life of the chicken, respectively. Embryonic expression of a-MSH in the RPE cells implies a possible role for the peptide in ocular development This is the first report demonstrating the expression of a-MSH in peripheral tissues in birds, and supports our hypothesis that avian a-MSH is a paracrine/autocrine hormone.2. Growth hormone (GH) is considered to play a role in the phatogenesis of diabetic retinopathy. RT-PCR and 5'RACE analysis identified a novel GH isoform expressed in the developing chicken eye. Immunocytochemistry revealed that the binding of the novel GH isoform, named as s-cGH, to GH receptors in the RPE cells is temporally regulated and correlates well with the production of a-MSH in the RPE cells during embryonic development, implying a possible involvement of s-CGH in the regulation of ocular development.3. The neural mechanisms involved in the compensatory hyperphagia exhibited by many vertebrate species after a fast are not fully understood but, in mammals, appear to involve neutritionally-sensitive neurons that co-express neuropeptide Y (NPY) and agouti-related protein (AGRP) in the infundibular hypothalamus. We investigated whether these neurons have been evolutionarily conserved in a non-mammalian vertebrate, the Japanese quail. Double-label in situ hybridization revealed that majority of NPY neurons in the infundibular nucleus co-express AGRP mRNA, indicating that this cell type has been neuroanatomically and functionally conserved during vertebrate evolution. .