Institute for Biomedical Sciences, Center for Inflammation, Immunity and Infection, Digestive Disease Research Group, Georgia State University, Atlanta, GA, USA.
Center of Research on Inflammation, U1149 INSERM, Paris, France.
NPJ Biofilms Microbiomes. 2020 Jul 21;6(1):27. doi: 10.1038/s41522-020-0137-y.
Numerous studies of knockout mice find impacts on microbiota composition that influence host phenotype. However, such differences can vanish when KO mice are compared directly to WT littermates, suggesting these differences do not reflect the genetic deletion per se but microbiota composition drifting over generations. Hence, our hypothesis that absence of di/tri-peptide transporter PepT1 altered microbiota composition resulting in resistance to colitis compelled scrutiny. In this study, we used PepT1 and WT founder mice bred separately for multiple generations. Such mice were then bred to each other to generate F1 PepT1 and WT littermates, which were then bred within their genotype to generate F2, F3, and F4, offspring. Here we report that founder PepT1 mice were, relative to their WT counterparts, resistant to DSS colitis. Such resistance was associated with alterations in gut microbiota, which, when transplanted to germfree mice, was sufficient to transfer resistance to colitis. Such differences were not observed when comparing F1 PepT1 to F1 WT littermates but rather, returned gradually over subsequent generations such that, relative to their F4 WT controls, F4 PepT1 displayed microbiota composition and colitis-resistant phenotype nearly identical to the founder PepT1 mice. Our findings indicate a role for PepT1 in influencing microbiota composition and, consequently, proneness to colitis and cancer. Overall, our study indicates that littermate-controlled experiments can be insufficient for assessing microbiota-dependent phenotypes and prevent a full comprehension of genotype-driven phenomena. Rather, impact of a single genetic alteration on microbiota and host phenotype may take generations to manifest.
大量研究敲除小鼠发现，微生物群落组成的变化会影响宿主表型。然而，当 KO 小鼠与 WT 同窝仔鼠直接比较时，这些差异可能会消失，这表明这些差异并不反映基因缺失本身，而是几代人之间微生物群落组成的漂移。因此，我们的假设是，二肽/三肽转运蛋白 PepT1 的缺失改变了微生物群落组成，导致对结肠炎的抵抗，这一假设迫使我们进行仔细审查。在这项研究中，我们使用 PepT1 和 WT 奠基者小鼠分别繁殖了多代。然后，将这些小鼠相互交配，产生 F1 PepT1 和 WT 同窝仔鼠，然后在其基因型内繁殖，产生 F2、F3 和 F4 后代。在这里，我们报告说，与 WT 对照相比，奠基者 PepT1 小鼠对 DSS 结肠炎具有抗性。这种抗性与肠道微生物群的改变有关，当将其移植到无菌小鼠中时，足以将结肠炎的抗性转移。当比较 F1 PepT1 与 F1 WT 同窝仔鼠时，没有观察到这种差异，而是在随后的几代中逐渐恢复，与 F4 WT 对照相比，F4 PepT1 显示出的微生物群落组成和结肠炎抗性表型几乎与奠基者 PepT1 小鼠相同。我们的研究结果表明 PepT1 在影响微生物群落组成方面发挥作用，因此，容易发生结肠炎和癌症。总的来说，我们的研究表明，同窝仔控制实验可能不足以评估依赖微生物群的表型，并且无法全面理解基因型驱动的现象。相反，单个遗传改变对微生物群和宿主表型的影响可能需要几代时间才能显现。
