Department of Psychology, College of Arts and Sciences, The Ohio State University, Columbus, OH 43210.
Department of Psychology, College of Arts and Sciences, The Ohio State University, Columbus, OH 43210
eNeuro. 2022 Apr 20;9(2). doi: 10.1523/ENEURO.0422-21.2022. Print 2022 Mar-Apr.
Inducible Cre recombinase facilitates temporal control of genetic recombination in numerous transgenic model systems, a feature which has made it a popular tool for adult neurogenesis studies. One of the most common forms of inducible Cre, CreER, requires activation by the selective estrogen receptor modulator tamoxifen (TAM) to initiate recombination of LoxP-flanked sequences. To date, most studies deliver TAM via intraperitoneal injection. But the introduction of TAM-infused commercial chows has recently expanded the possible modes of TAM delivery. Despite the widespread use of TAM-inducible genetic models in adult neurogenesis research, the comparative efficiency and off-target effects of TAM administration protocols is surprisingly infrequently studied. Here, we compare a standard, 5 d TAM injection regimen with voluntary consumption of TAM-infused chow. First, we used adult NestinCreER;Rosa-LoxP-STOP-LoxP-EYFP reporter mice to show that two weeks of TAM chow and 5 d of injections led to LoxP recombination in a similar phenotypic population of neural stem and progenitor cells (NSPCs) in the adult dentate gyrus. However, TAM chow resulted in substantially less overall recombination than injections. TAM administration also altered adult neurogenesis, but in different ways depending on administration route: TAM injection disrupted neural progenitor cell proliferation three weeks after TAM, whereas TAM chow increased neuronal differentiation of cells generated during the diet period. These findings provide guidance for selection of TAM administration route and appropriate controls in adult neurogenesis studies using TAM-inducible Cre mice. They also highlight the need for better understanding of off-target effects of TAM in other neurologic processes and organ systems.
诱导型 Cre 重组酶在许多转基因模型系统中促进遗传重组的时间控制，这一特性使其成为成年神经发生研究的常用工具。最常见的诱导型 Cre 之一 CreER 需要选择性雌激素受体调节剂他莫昔芬 (TAM) 的激活才能启动 LoxP 侧翼序列的重组。迄今为止，大多数研究通过腹腔注射给药 TAM。但最近，TAM 注入商业饲料的引入扩大了 TAM 给药的可能模式。尽管 TAM 诱导的遗传模型在成年神经发生研究中被广泛使用，但 TAM 给药方案的比较效率和脱靶效应却很少被研究。在这里，我们将标准的 5d TAM 注射方案与 TAM 注入饲料的自愿消耗进行了比较。首先，我们使用成年 NestinCreER;Rosa-LoxP-STOP-LoxP-EYFP 报告小鼠表明，2 周的 TAM 饲料和 5d 的注射导致成年齿状回中类似表型的神经干细胞和祖细胞 (NSPC) 中的 LoxP 重组。然而，TAM 饲料导致的总体重组明显少于注射。TAM 给药也改变了成年神经发生，但根据给药途径而有所不同：TAM 注射在 TAM 后 3 周破坏神经祖细胞增殖，而 TAM 饲料增加了饮食期间产生的细胞的神经元分化。这些发现为使用 TAM 诱导型 Cre 小鼠的成年神经发生研究中 TAM 给药途径和适当对照的选择提供了指导。它们还强调了需要更好地了解 TAM 在其他神经过程和器官系统中的脱靶效应。
