RNAseq analysis of skeletal muscle transcriptomes from wild-type, LONP1 skeletal muscle specific knockout (LONP1 mKO) and LONP1ATF4 skeletal muscle double-knockout (LONP1ATF4 DmKO) mice.

Studying the molecular basis for the skeletal muscle mitochondrial stress response could potentially be targeted to counteract metabolic disorders such as obesity. We uncovered a crucial role for the mitochondrial protease LONP1 in controlling the muscle mitochondrial proteostasis stress response that governs systemic metabolic homeostasis. Skeletal muscle-specific ablation of LONP1 led to broad genomic reprogramming of muscle and protected the mice from HFD-induced obesity. To thoroughly analyze pathways that are affected by ATF4 deficiency in the context of LONP1 mKO, we performed RNA-Seq transcriptome analysis of skeletal muscles from WT, LONP1 mKO and LONP1ATF4 DmKO mice. We identified a total of 3017 differentially expressed genes with a cutoff of 1.5-fold, and p < 0.05. Surprisingly, we found that ATF4 loss blunted a subset of regulated genes in LONP1 mKO muscles, whereas the majority of differentially regulated genes in LONP1 mKO muscles were not affected by ATF4 ablation. GO analysis of ATF4-dependent genes regulated by LONP1 ablation revealed significant enrichment in amino acid metabolic processes, Interestingly, however, LONP1 deficiency induced activation of muscle UPR and UPR-related RNA processing as well as myokine pathways were not affected by ATF4 ablation. Therefore, our results highlight a ATF4-independent mechanism in mediating the UPRmt in mammals. Gastrocnemius muscle mRNA profiles of 6-week-old WT, LONP1 mKO and LONP1ATF4 DmKO mice were generated by deep sequencing, in duplicate, using Illumina HiSeq 4000.