Taking advantage of their ability to integrate their genomes into the host genome, lentiviruses have been used to rapidly produce transgenic mice in biomedical research. In most cases, transgenes delivered by lentiviral vectors have resisted silencing mediated by epigenetic modifications in mice. However, some studies revealed that methylation caused decreased transgene expression in mice. Therefore, there is conflicting evidence regarding the methylation-induced silencing of transgenes delivered by lentiviral transduction in mice. In this study, we present evidence that the human TTR transgene was silenced by DNA methylation in the liver of a transgenic mouse model generated by lentiviral transduction. The density of methylation on the transgene was increased during reproduction, and the expression of the transgene was completely silenced in mice of the F2 generation. Interestingly, 5-azacytidine (5-AzaC), a methyltransferase inhibitor, potently reactivated the silenced genes in neonatal mice whose hepatocytes were actively proliferating and led to stable transgene expression during development. However, 5-AzaC did not rescue liver transgene expression when administered to adult mice. Moreover, 5-AzaC at the given dose had low developmental toxicity in the newborn mice. In summary, we demonstrate the methylation-induced silencing of an exogenous gene in the liver of a mouse model generated by lentiviral transduction and show that the silenced transgene can be safely and efficiently reactivated by 5-AzaC treatment, providing an alternative way to obtain progeny with stable transgene expression in the case of the methylation of exogenous genes in transgenic mice generated by lentiviral transduction.

利用它们将基因组整合到宿主基因组中的能力，慢病毒已被用于在生物医学研究中快速生产转基因小鼠。在大多数情况下，慢病毒载体传递的转基因抵抗小鼠表观遗传修饰介导的沉默。然而，一些研究表明甲基化导致小鼠转基因表达降低。因此，关于甲基化诱导小鼠慢病毒转导传递的转基因沉默的证据相互矛盾。在这项研究中，我们提供的证据表明人类TTR通过慢病毒转导产生的转基因小鼠模型肝脏中的 DNA 甲基化使转基因沉默。转基因的甲基化密度在繁殖过程中增加，转基因的表达在 F2 代小鼠中完全沉默。有趣的是，甲基转移酶抑制剂 5-氮杂胞苷 (5-AzaC) 有效地重新激活了新生小鼠的沉默基因，这些小鼠的肝细胞正在积极增殖，并在发育过程中导致稳定的转基因表达。然而，当对成年小鼠给药时，5-AzaC 并没有挽救肝脏转基因表达。此外，给定剂量的 5-AzaC 在新生小鼠中具有低发育毒性。总之，