Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
Endocrinology. 2020 Aug 1;161(8). doi: 10.1210/endocr/bqaa054.
Targeted gene ablation studies of the endocrine pancreas have long suffered from suboptimal Cre deleter strains. In many cases, Cre lines purportedly specific for beta cells also displayed expression in other islet endocrine cells or in a subset of neurons in the brain. Several pancreas and endocrine Cre lines have experienced silencing or mosaicism over time. In addition, many Cre transgenic constructs were designed to include the hGH mini-gene, which by itself increases beta-cell replication and decreases beta-cell function. More recently, driver lines with Cre or CreER inserted into the Ins1 locus were generated, with the intent of producing β cell-specific Cre lines with faithful recapitulation of insulin expression. These lines were bred in multiple labs to several different mouse lines harboring various lox alleles. In our hands, the ability of the Ins1-Cre and Ins1-CreER lines to delete target genes varied from that originally reported, with both alleles displaying low levels of expression, increased levels of methylation compared to the wild-type allele, and ultimately inefficient or absent target deletion. Thus, caution is warranted in the interpretation of results obtained with these genetic tools, and Cre expression and activity should be monitored regularly when using these lines.
靶向基因敲除研究的内分泌胰腺长期以来一直受到不理想的 Cre 缺失株的困扰。在许多情况下，据称专门针对β细胞的 Cre 系也在其他胰岛内分泌细胞或大脑中的一组神经元中表达。随着时间的推移，一些胰腺和内分泌 Cre 系经历了沉默或嵌合体。此外，许多 Cre 转基因构建体被设计为包含 hGH 微基因，该基因本身会增加β细胞的复制并降低β细胞的功能。最近，具有 Cre 或 CreER 插入 Ins1 基因座的驱动系被产生，目的是产生具有胰岛素表达忠实再现的β细胞特异性 Cre 系。这些系在多个实验室中与携带各种lox 等位基因的多种不同小鼠系进行了杂交。在我们的手中，Ins1-Cre 和 Ins1-CreER 系删除靶基因的能力与最初报道的不同，两个等位基因的表达水平较低，与野生型等位基因相比，甲基化水平增加，最终目标基因缺失效率低下或缺失。因此，在使用这些遗传工具获得的结果的解释中需要谨慎，并且在使用这些系时应定期监测 Cre 的表达和活性。
