MIWI2 Regulates Mitochondrial Gene Expression During Influenza and Exacerbates Disease Outcome

The airway epithelium, consisting of diverse cell types, plays a vital role in defending against respiratory viruses. MIWI2 multiciliated (M2MC) cells are a rare subpopulation of multiciliated cells distinguished by the expression of MIWI2, the mouse analogous PIWIL4 argonaute family protein. While recognized for its role in repressing retrotransposons during spermatogenesis and regulating viral RNA in mosquitos, the function of MIWI2 in M2MC cells remains poorly understood. This study explores the transcriptomic changes in retrotransposons, viral RNAs, and host genes in an effort to elucidate MIWI2’s role in the airway. M2MC and nonM2MC cells were sorted from digested lungs of MIWI2 haplosufficient (Miwi2+/tom) and deficient (Miwi2tom/tom) mice intratracheally instilled with saline or mouse adapted A/Puerto Rico/8/1934 (PR8) IAV three days post infection. Our findings indicated that retrotransposon and viral RNA expression is independent of MIWI2 expression. However, MIWI2 deficiency decreased mitochondrial and ribosomal gene expression in M2MC cells during PR8 infection. In addition, a decrease in small RNAs mapped to nuclear mitochondrial (NuMT) DNA was observed in saline treated MIWI2 expressing cells. These findings were then followed up by flow cytometry studies where an increase in intracellular reactive oxygen species (ROS) was observed in PR8 infected multiciliated cells from Miwi2tom/tom mice. In addition, Miwi2tom/tom mice experience decreased viral titer and RNA 7 days post infection and recovered faster in percent body weight compared to wild-type and Miwi2+/tom mice. These studies suggest that MIWI2 exacerbates IAV outcomes by regulating mitochondrial gene expression and function. These results reveal a novel role for MIWI2 in somatic cells and propose MIWI2/PIWIL4 as a potential biomarker for susceptibility to severe respiratory infections. Understanding MIWI2-dependent pathways could lead to new therapeutic targets for respiratory viral infections.