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

1.α-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。通过RT-PCR、免疫细胞化学和原位杂交，我们鉴定了a-MSH在眼睛中的表达，它在发育中的鸡的时间和空间上受到调控。结果表明，视网膜色素上皮细胞(RPE细胞)和视锥细胞分别是鸡胚胎和出生后眼内a-MSH的来源。α-MSH在RPE细胞中的胚胎表达提示该肽可能在眼发育中起作用。这是首次报道鸟类外周组织中α-MSH的表达，并支持我们的假设，即禽α-MSH是一种旁分泌/自分泌激素。生长激素(GH)被认为在糖尿病视网膜病变的发病机制中起作用。RT-PCR和5‘RACE分析证明，在发育中的鸡眼中表达了一种新的生长激素亚型。免疫细胞化学结果显示，新的生长激素异构体S-CGH与视网膜色素上皮细胞中GH受体的结合受时间调控，并与胚胎发育过程中视网膜色素上皮细胞中α-MSH的产生密切相关，提示S-CGH可能参与了眼发育的调控。许多脊椎动物禁食后出现代偿性吞噬反应的神经机制尚不完全清楚，但在哺乳动物中，似乎涉及到漏斗状下丘脑中共表达神经肽Y(NPY)和刺鼠相关蛋白(AGRP)的神经敏感神经元。我们调查了这些神经元在进化上是否在非哺乳类脊椎动物日本鹌鹑中得到了保守。双标记原位杂交结果显示，漏斗核中的NPY神经元大部分共表达AGRP mRNA，表明在脊椎动物进化过程中，这种细胞在神经解剖学和功能上都是保守的。。

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. .