瘦蛋白基因(leptin)在哺乳動(dòng)物的能量平衡和生殖調(diào)控等方面有重要作用。以前對(duì)該基因的研究主要集中于它對(duì)人類(lèi)健康,，尤其是肥胖癥方面,。而對(duì)該基因所具有的其它可能的新功能卻知之甚少。
中國(guó)科學(xué)院昆明動(dòng)物研究所張亞平院士課題組和云南大學(xué)于黎研究員，博士研究生靳偉等測(cè)定了海洋哺乳動(dòng)物--鯨目代表物種的leptin基因,，并結(jié)合55條網(wǎng)上已有哺乳動(dòng)物leptin序列進(jìn)行研究,。研究結(jié)果發(fā)現(xiàn)在鯨目中的齒鯨亞目祖先枝和食肉目水生鰭腳類(lèi)中的海豹科祖先枝都發(fā)現(xiàn)了正選擇作用和正選擇位點(diǎn)。而鯨目中的須鯨亞目祖先枝和食肉目中水生鰭腳類(lèi)中的海獅科祖先枝都沒(méi)有發(fā)現(xiàn)正選擇作用,。提示leptin基因在海洋哺乳動(dòng)物的特定類(lèi)群中,，包括須鯨亞目和海豹科物種中產(chǎn)生了新的組織特異性和新功能，如與深水潛水有關(guān)的呼吸系統(tǒng)功能適應(yīng),。此外,，我們還對(duì)與瘦蛋白結(jié)合的瘦蛋白受體（leptin receptor）基因進(jìn)行了分析，研究結(jié)果并沒(méi)有在鯨目和食肉目鰭腳類(lèi)中發(fā)現(xiàn)正選擇,。因此leptin和leptin receptor基因之間不存在共進(jìn)化,。本研究為哺乳動(dòng)物從陸地到海洋轉(zhuǎn)變過(guò)程中的leptin進(jìn)化和可能具有的新功能提供了重要信息。
研究結(jié)果已發(fā)表在國(guó)際刊物《PLOS ONE》上(Yu et al. 2011. 6: e26579),。（生物谷 Bioon.com）
doi:10.1371/journal.pone.0026579
PMC:
PMID:
Evidence for Positive Selection on the Leptin Gene in Cetacea and Pinnipedia
Li Yu, Wei Jin, Xin Zhang, Ding Wang, Jin-song Zheng, Guang Yang, Shi-xia Xu, Soochin Cho, Ya-ping Zhang
The leptin gene has received intensive attention and scientific investigation for its importance in energy homeostasis and reproductive regulation in mammals. Furthermore, study of the leptin gene is of crucial importance for public health, particularly for its role in obesity, as well as for other numerous physiological roles that it plays in mammals. In the present work, we report the identification of novel leptin genes in 4 species of Cetacea, and a comparison with 55 publicly available leptin sequences from mammalian genome assemblies and previous studies. Our study provides evidence for positive selection in the suborder Odontoceti (toothed whales) of the Cetacea and the family Phocidae (earless seals) of the Pinnipedia. We also detected positive selection in several leptin gene residues in these two lineages. To test whether leptin and its receptor evolved in a coordinated manner, we analyzed 24 leptin receptor gene (LPR) sequences from available mammalian genome assemblies and other published data. Unlike the case of leptin, our analyses did not find evidence of positive selection for LPR across the Cetacea and Pinnipedia lineages. In line with this, positively selected sites identified in the leptin genes of these two lineages were located outside of leptin receptor binding sites, which at least partially explains why co-evolution of leptin and its receptor was not observed in the present study. Our study provides interesting insights into current understanding of the evolution of mammalian leptin genes in response to selective pressures from life in an aquatic environment, and leads to a hypothesis that new tissue specificity or novel physiologic functions of leptin genes may have arisen in both odontocetes and phocids. Additional data from other species encompassing varying life histories and functional tests of the adaptive role of the amino acid changes identified in this study will help determine the factors that promote the adaptive evolution of the leptin genes in marine mammals.
