Roehe R, Plastow G S, Knap P W
Institut für Tierzucht und Tierhaltung, Christian-Albrechts-Universität zu Kiel, 24118 Kiel.
Homo. 2003;54(2):119-31. doi: 10.1078/0018-442x-00064.
After 30 years of selection, breeding of the pig breed sus scrofa Piétrain has resulted in reduced backfat thickness (from 3.2 to 1.9 mm) and increased loin muscle area (40 to 60 cm2) which indicates high genetic determination of these body composition traits. The use of sophisticated quantitative genetic methods that include all genetic relationships of large populations has led to a high response to selection of these traits. Selection on feed intake, lean and fat tissue growth using nonlinear functions to optimise these traits during the entire growth period in a biological model offers the opportunity to further improve total genetic potential. Protein and lipid deposition rates during the entire growth period have to be known for this biological model to be applied; thus knowledge of the genetic background of these traits is of high economic value. With the use of molecular genetic methods, such as candidate gene and genome scan approaches, the identification of genes for obesity and growth can be obtained. In sus scrofa, candidate genes associated with obesity and growth include Leptin Receptor, Melanocortin-4 Receptor, Agouti related protein, Heart fatty acid binding protein 3, and Insulin-like growth factor 2. Some of these candidate genes also explain variation in obesity levels in humans. Initial genome-wide scans have identified quantitative trait loci (QTL) on chromosomes 1, 4, 5, 7 and X for obesity and on chromosomes 1, 4, 7, 8, 13 and 18 for growth. Physiological candidate genes and predispositional QTL for obesity are not always located on the same chromosome; this is known the "polygenic paradox". Use of a nonlinear growth function is recommended in order to give more insight into the physiological regulation of obesity traits. Sus scrofa is an excellent model organism to examine the genetic regulation of obesity. The conservation of DNA sequence and chromosomal segments between sus scrofa and homo sapiens will permit easy transfer of results to human studies.
经过30年的选育，皮特兰猪种（Sus scrofa Piétrain）的背膘厚度降低（从3.2毫米降至1.9毫米），腰肌面积增加（从40平方厘米增至60平方厘米），这表明这些身体组成性状具有较高的遗传决定性。使用复杂的数量遗传学方法，包括考虑大群体的所有遗传关系，已导致对这些性状的选择有较高响应。在生物模型中，利用非线性函数对整个生长周期的采食量、瘦肉和脂肪组织生长进行选择，为进一步提高总遗传潜力提供了机会。要应用这个生物模型，必须了解整个生长周期的蛋白质和脂质沉积率；因此，了解这些性状的遗传背景具有很高的经济价值。通过使用分子遗传学方法，如候选基因和基因组扫描方法，可以鉴定出与肥胖和生长相关的基因。在猪（Sus scrofa）中，与肥胖和生长相关的候选基因包括瘦素受体、黑皮质素-4受体、刺鼠相关蛋白、心脏脂肪酸结合蛋白3和胰岛素样生长因子2。其中一些候选基因也解释了人类肥胖水平的差异。最初的全基因组扫描已经确定了1号、4号、5号、7号和X染色体上与肥胖相关的数量性状位点（QTL），以及1号、4号、7号、8号、13号和18号染色体上与生长相关的数量性状位点。肥胖的生理候选基因和易感性QTL并不总是位于同一条染色体上；这就是所谓的“多基因悖论”。建议使用非线性生长函数，以便更深入地了解肥胖性状的生理调节。猪（Sus scrofa）是研究肥胖遗传调控的优秀模式生物。猪（Sus scrofa）和智人之间DNA序列和染色体片段的保守性将使研究结果易于转化为人类研究。
