Mice with a malignant hyperthermia mutation (Y522S) in the ryanodine receptor (RyR1) display muscle contractures, rhabdomyolysis, and death in response to elevated environmental temperatures. We demonstrate that this mutation in RyR1 causes Ca(2+) leak, which drives increased generation of reactive nitrogen species (RNS). Subsequent S-nitrosylation of the mutant RyR1 increases its temperature sensitivity for activation, producing muscle contractures upon exposure to elevated temperatures. The Y522S mutation in humans is associated with central core disease. Many mitochondria in the muscle of heterozygous Y522S mice are swollen and misshapen. The mutant muscle displays decreased force production and increased mitochondrial lipid peroxidation with aging. Chronic treatment with N-acetylcysteine protects against mitochondrial oxidative damage and the decline in force generation. We propose a feed-forward cyclic mechanism that increases the temperature sensitivity of RyR1 activation and underlies heat stroke and sudden death. The cycle eventually produces a myopathy with damaged mitochondria.

and collect data. BHC helped generate Tug1-transgenic mice and edit the manuscript. PAO helped edit the manuscript, and FRD oversaw experiments, prepared the manuscript, and provided guidance on overall project design.

Recent advances have led to a greater appreciation of how mitochondrial dysfunction contributes to diverse acute and chronic pathologies. Indeed, mitochondria have received increasing attention as a therapeutic target in a variety of diseases since they serve as key regulatory hubs uniquely situated at crossroads between multiple cellular processes. This review provides an overview of the role of mitochondrial dysfunction in chronic kidney disease (CKD) with special emphasis on its role in the development of diabetic nephropathy (DN). We will examine the current understanding on the molecular mechanisms that cause mitochondrial dysfunction in the kidney and describe the impact of mitochondrial damage on kidney function. The new concept that mitochondrial shape and structure is intimately linked with its function in the kidneys is discussed. Furthermore, the mechanisms that translate cellular cues and demands into mitochondrial remodeling and cellular damage, including the role of microRNAs and lncRNAs, are examined with the final goal of identifying mitochondrial targets to improve treatment of patients with chronic kidney diseases.

Mitochondrial fission has been linked to the pathogenesis of diabetic nephropathy (DN). However, how mitochondrial fission affects progression of DN in vivo is unknown. Here, we report the effect of conditional podocyte-specific deletion of dynamin-related protein 1 (Drp1), an essential component of mitochondrial fission, on the pathogenesis and progression of DN. Inducible podocyte-specific deletion of Drp1 in diabetic mice decreased albuminuria and improved mesangial matrix expansion and podocyte morphology. Ultrastructure analysis revealed a significant increase in fragmented mitochondria in the podocytes of wild-type diabetic mice but a marked improvement in mitochondrial structure in Drp1-null podocytes of diabetic mice. When isolated from diabetic mice and cultured in high glucose, Drp1-null podocytes had more elongated mitochondria and better mitochondrial fitness associated with enhanced oxygen consumption and ATP production than wild-type podocytes. Furthermore, administration of a pharmacologic inhibitor of Drp1, Mdivi1, significantly blunted mitochondrial fission and rescued key pathologic features of DN in mice. Taken together, these results provide novel correlations between mitochondrial morphology and the progression of DN and point to Drp1 as a potential therapeutic target in DN.

The piggyBac transposon system represents a promising non-viral tool for gene delivery and discovery, and may also be of value for clinical gene therapy. PiggyBac is a highly efficient integrating vector that stably transfects (~40%) of primary human T cells for potential adoptive immunotherapy applications. To evaluate the potential genotoxicity of piggyBac, we compared 228 integration sites in primary human T cells to integrations in two other human derived cell lines (HEK293 and HeLa) and randomly simulated integrations into the human genome. Our results revealed distinct differences between cell types. PiggyBac had a non-random integration profile and a preference for transcriptional units (~50% into RefSeq genes in all cell types), CpG islands (18% in T cells and 8% in other human cells), and transcriptional start sites (TSS) (< 5kb, 16–20% in all cell types). PiggyBac also preferred TTAA but not AT rich regions of the human genome. We evaluated the expression of mapped genes into which piggyBac integrated, and found selection of more active genes in primary human T cells compared to other human cell types, possibly due to concomitant T cell activation during transposition. Importantly, we found that in comparison to what has been reported for gammaretroviral and human lenitviral vectors, piggyBac had decreased integration frequency into or within 50kb of the TSS of known proto-oncogenes. Hence the piggyBac non-viral gene delivery system appears to represent a promising gene transfer system for clinical applications using human T lymphocytes.