Not All C57BL/6 Substrains Are Created Equal

对来自JAX的80个C57BL/6GEM中缺失多个外显子的突变的烟酰胺核苷酸转氢酶(NNT)等位基因进行基因分型，发现27个GEM(34%)实际上含有完整的NNT基因，这在C57BL/6小鼠的所有其他亚株中都存在。进一步的研究表明，来自JAX的C57BL/6J亚株对醋氨酚诱导的肝损伤(AILI)的敏感性显著低于其他供应商携带完整NNT基因的C57BL/6小鼠的其他三个亚株。这一发现非常重要，因为它解释了文献中关于c-Jun氨基末端激酶2(JNK2)信号在AILI中的作用的相互矛盾的结果。在一项研究中，发现JNK2基因缺失的GEM比对照C57BL/6J小鼠更容易感染AILI，这表明JNK2对AILI具有保护作用。其他研究人员得出结论，JNK2与AILI的病因学有关，因为他们发现JNK2基因缺陷的小鼠比野生型C57BL/6窝产仔更不容易感染AILI。我们发现来自JAX的JNK2基因缺陷小鼠并不是在C57BL/6J背景上，而是回交到一个含有完整NNT基因的C57BL/6亚系，该亚系比JNK2基因缺陷研究中用作对照的C57BL/6J亚系更容易感染ALI。正是这种错配导致了JNK2对AILI具有保护作用的错误结论，因为无论JNK2基因如何，具有完整NNT基因的C57BL/6亚株上的JNK2缺陷小鼠天生比C57BL/6J小鼠对AILI更敏感。 最近，用醋氨酚处理的JAX C57BL/6J小鼠和Taconic的C57BL/6小鼠的肝脏外显子阵列进行的全基因组表达分析表明，这两个亚株之间在表达基因和剪接变体方面存在大量差异。 结论：所有生物医学研究人员都应该意识到C57BL/6亚株的遗传和表型差异。当在C57BL/6背景下使用GEM进行研究时，这方面的知识尤为重要。GEM与错误的C57BL/6亚株对照的缺失配对可能会导致错误和误导性的发现。另一方面，研究C57BL/6亚株的遗传和表型差异可能有助于识别可能在多种病理过程中发挥作用的重要危险因素。

Genotyping 80 C57BL/6 GEM from JAX for a mutant nicotinamide nucleotide transhydrogenase (Nnt) allele missing several exons, which is specific to the C57BL/6J substrain, revealed that 27 GEM (34%) actually contained the intact Nnt gene, which is found in all other substrains of C57BL/6 mice. Further studies revealed that the C57BL/6J substrain from JAX was significantly less susceptible to acetaminophen-induced liver injury (AILI) than three other substrains of C57BL/6 mice carrying the intact Nnt gene from other vendors. This finding is very important because it explains the conflicting results in the literature as to the role c-Jun N-terminal kinase 2 (JNK2)-signaling in AILI. In one study, GEM deficient in JNK2 were found to be more susceptible to AILI than control C57BL/6J mice, suggesting that JNK2 had a protective role in AILI. Other researchers concluded that JNK2 was involved in the etiology of AILI because they found that mice deficient in JNK2 were less susceptible to AILI than wild-type C57BL/6 littermates. We discovered that the JNK2 deficient mice from JAX were not on a C57BL/6J background, but instead backcrossed to a C57BL/6 substrain containing the intact Nnt gene that was more susceptible to AILI than the C57BL/6J substrain used as controls in the studies with GEM deficient in JNK2. It is this mispairing that lead to the incorrect conclusion that JNK2 was protective against AILI because the JNK2 deficient mice on a C57BL/6 substrain possessing the intact Nnt gene were inherently more susceptible to AILI than C57BL/6J mice irrespective of the JNK2 gene. Recent genome-wide expression analysis with exon arrays of livers from acetaminophen-treated C57BL/6J mice from JAX and C57BL/6 mice from Taconic containing the intact Nnt gene revealed numerous differences in expressed genes and spliced variants between the two substrains. Conclusion: All biomedical researchers should be aware of the genetic and phenotypic differences in C57BL/6 substrains. This knowledge is particularly important when doing studies with GEM on a C57BL/6 background. Missing pairing of GEM with the wrong C57BL/6 substrain control can lead to erroneous and misleading findings. On the other hand, studying the genetic and phenotypic difference in C57BL/6 substrains may lead to the identification of important risk factors that may play a role in a variety pathological processes.