Genetically modified (GM) pigs hold great promises for pig genetic improvement, human health and life science. When GM pigs are produced, selectable marker genes (SMGs) are usually introduced into their genomes for host cell or animal recognition. However, the SMGs that remain in GM pigs might have multiple side effects. To avoid the possible side effects caused by the SMGs, they should be removed from the genome of GM pigs before their commercialization. The Cre recombinase is commonly used to delete the LoxP sites-flanked SMGs from the genome of GM animals. Although SMG-free GM pigs have been generated by Cre-mediated recombination, more efficient and cost-effective approaches are essential for the commercialization of SMG-free GM pigs. In this article we describe the production of a recombinant Cre protein containing a cell-penetrating and a nuclear localization signal peptide in one construct. This engineered Cre enzyme can efficiently excise the LoxP-flanked SMGs in cultured fibroblasts isolated from a transgenic pig, which then can be used as nuclear donor cells to generate live SMG-free GM pigs harboring a desired transgene by somatic cell nuclear transfer. This study describes an efficient and far-less costly method for production of SMG-free GM pigs.

中文翻译：

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通过工程化 Cre 重组酶从转基因猪基因组中有效删除 LoxP 侧翼选择标记基因。

转基因（GM）猪对猪的遗传改良、人类健康和生命科学有着巨大的希望。在生产转基因猪时，通常将选择标记基因 (SMG) 引入其基因组中，以供宿主细胞或动物识别。然而，留在转基因猪体内的 SMG 可能有多种副作用。为避免 SMG 可能引起的副作用，应在商业化之前将其从转基因猪的基因组中移除。Cre 重组酶通常用于从转基因动物的基因组中删除 LoxP 位点侧翼的 SMG。尽管 Cre 介导的重组已经产生了不含 SMG 的转基因猪，但更有效和更具成本效益的方法对于不含 SMG 的转基因猪的商业化至关重要。在本文中，我们描述了在一个构建体中包含细胞穿透和核定位信号肽的重组 Cre 蛋白的生产。这种工程化的 Cre 酶可以有效地切除从转基因猪分离的培养成纤维细胞中的 LoxP 侧翼 SMG，然后可以将其用作核供体细胞，通过体细胞核移植产生含有所需转基因的无 SMG 转基因猪。本研究描述了一种生产无 SMG 转基因猪的有效且成本低得多的方法。