Integrated analysis of the molecular pathogenesis of FDXR-associated disease.

The mitochondrial flavoprotein ferredoxin reductase (FDXR) is required for biogenesis of iron-sulfur clusters and for steroidogenesis. Iron-sulfur (Fe-S) clusters are ubiquitous cofactors essential to various cellular processes, and an increasing number of disorders are associated with disruptions in the synthesis of Fe-S clusters. Our previous studies have demonstrated that hypomorphic mutations in FDXR cause a novel mitochondriopathy and optic atrophy in humans and mice, attributed in part to reduced function of the electron transport chain (ETC) as well as elevated production of reactive oxygen species (ROS). Inflammation and peripheral neuropathy are also hallmarks of this disease. In this paper, we demonstrate that FDXR mutation leads to significant optic transport defects that are likely to underlie optic atrophy, a major clinical presentation in FDXR patients, as well as a neurodegenerative loss of cells in the central nervous system (CNS). Molecular analysis indicates that FDXR mutation also leads to mitochondrial iron overload and an associated depolarization of the mitochondrial membrane, further supporting the hypothesis that FDXR mutations cause neurodegeneration by affecting FDXR\u27s critical role in iron homeostasis

Evaluation of tarsal injuries in C57BL/6J male mice.

Tarsal joint abnormalities have been observed in aged male mice on a C57BL background. This joint disease consists of calcaneal displacement, inflammation, and proliferation of car- tilage and connective tissue, that can progress to ankylosis of the joint. While tarsal pathol- ogy has been described previously in C57BL/6N substrains, as well as in STR/ort and B10. BR strain, no current literature describes this disease occurring in C57BL/6J mice. More importantly the behavioral features that may result from such a change to the joint have yet to be evaluated. This condition was observed in older male mice of the C57BL/6J lineage, around the age of 20 weeks or older, at a frequency of 1% of the population. To assess potential phenotypic sequela, this study sought to evaluate body weight, frailty assessment, home cage wheel running, dynamic weight bearing, and mechanical allodynia with and with- out the presence of pain relief with morphine. Overall mice with tarsal injuries had signifi- cantly higher frailty scores (p\u3c 0.05) and weighed less (p\u3c0.01) compared to unaffected mice. Affected mice had greater overall touch sensitivity (p\u3c0.05) and they placed more weight on their forelimbs (p\u3c0.01) compared to their hind limbs. Lastly, when housed with a running wheel, affected mice ran for a shorter length of time (p\u3c0.01) but tended to run a greater distance within the time they did run (p\u3c0.01) compared to unaffected mice. When tested just after being given morphine, the affected mice performed more similarly to unaf- fected mice, suggesting there is a pain sensation to this disease process. This highlights the importance of further characterizing inbred mouse mutations, as they may impact research programs or specific study goals

Assessing Healthspan and Lifespan Measures in Aging Mice: Optimization of Testing Protocols, Replicability, and Rater Reliability.

The relationship between chronological age (lifespan) and biological age (healthspan) varies amongst individuals. Understanding the normal trajectory and characteristic traits of aging mice throughout their lifespan is important for selecting the most reliable and reproducible measures to test hypotheses. The protocols herein describe assays used for aging studies at The Jackson Laboratory\u27s Mouse Neurobehavioral Phenotyping Facility and include assessments of frailty, cognition, and sensory (hearing, vision, olfaction), motor, and fine motor function that can be used for assessing phenotypes in aged mice across their lifespan as well as provide guidance for setting up and validating these behavioral measures. Researchers aiming to study aging phenotypes require access to aged mice as a reference when initiating these types of studies in order to observe normal aging characteristics that cannot be observed in young adult mouse populations. © 2018 by John Wiley & Sons, Inc

T Cells from NOD-PerIg Mice Target Both Pancreatic and Neuronal Tissue.

The CD27-CD70 costimulatory pathway is essential for the full activation of T cells, but some studies show that blocking this pathway exacerbates certain autoimmune disorders. In this study, we report on the impact of CD27-CD70 signaling on disease progression in the NOD mouse model of type 1 diabetes (T1D). Specifically, our data demonstrate that CD70 ablation alters thymocyte selection and increases circulating T cell levels. CD27 signaling was particularly important for the thymic development and peripheral homeostasis of Foxp3+Helios+ regulatory T cells, which likely accounts for our finding that CD70-deficient NOD mice develop more-aggressive T1D onset. Interestingly, we found that CD27 signaling suppresses the thymic development and effector functions of T1D-protective invariant NKT cells. Thus, rather than providing costimulatory signals, the CD27-CD70 axis may represent a coinhibitory pathway for this immunoregulatory T cell population. Moreover, we showed that a CD27 agonist Ab reversed the effects of CD70 ablation, indicating that the phenotypes observed in CD70-deficient mice were likely due to a lack of CD27 signaling. Collectively, our results demonstrate that the CD27-CD70 costimulatory pathway regulates the differentiation program of multiple T cell subsets involved in T1D development and may be subject to therapeutic targeting

Biallelic mutations in the ferredoxin reductase gene cause novel mitochondriopathy with optic atrophy.

Iron-sulfur (Fe-S) clusters are ubiquitous cofactors essential to various cellular processes, including mitochondrial respiration, DNA repair, and iron homeostasis. A steadily increasing number of disorders are being associated with disrupted biogenesis of Fe-S clusters. Here, we conducted whole-exome sequencing of patients with optic atrophy and other neurological signs of mitochondriopathy and identified 17 individuals from 13 unrelated families with recessive mutations in FDXR, encoding the mitochondrial membrane-associated flavoprotein ferrodoxin reductase required for electron transport from NADPH to cytochrome P450. In vitro enzymatic assays in patient fibroblast cells showed deficient ferredoxin NADP reductase activity and mitochondrial dysfunction evidenced by low oxygen consumption rates (OCRs), complex activities, ATP production and increased reactive oxygen species (ROS). Such defects were rescued by overexpression of wild-type FDXR. Moreover, we found that mice carrying a spontaneous mutation allelic to the most common mutation found in patients displayed progressive gait abnormalities and vision loss, in addition to biochemical defects consistent with the major clinical features of the disease. Taken together, these data provide the first demonstration that germline, hypomorphic mutations in FDXR cause a novel mitochondriopathy and optic atrophy in humans. Hum Mol Genet 2017 Dec 15; 26(24):4937-4950