Biology subjects

Wagner, K. R.

Publications and source records attributed to Wagner, K. R..

4 recordsLinked to original sources

bioRxiv2021

Loss of TDP-43 function and rimmed vacuoles persist after T cell depletion in a xenograft model of sporadic inclusion body myositis

Sporadic inclusion body myositis (IBM) is the most common acquired muscle disease in adults over age 50, yet it remains unclear whether the disease is primarily driven by T cell-mediated autoimmunity. IBM muscle biopsies exhibit nuclear clearance and cytoplasmic aggregation of TDP-43 in muscle cells, a pathologic finding observed initially in neurodegenerative disease, and nuclear loss of TDP-43 in neurons causes aberrant RNA splicing. Here, we show that loss of TDP-43 splicing repression, as determined by inclusion of cryptic exons, occurs in skeletal muscle of IBM patients. Out of 119 muscle biopsies tested, RT-PCR-mediated detection of cryptic exon expression is 84% sensitive and 99% specific for diagnosing IBM, indicating utility as a functional and diagnostic biomarker. To determine the role of T cells in pathogenesis, we generated a novel xenograft model by transplanting human IBM muscle into the hindlimb of immunodeficient mice. Xenografts from IBM patients display robust regeneration of human myofibers and recapitulate both inflammatory and degenerative features of the disease. Myofibers in IBM xenografts are invaded by human, oligoclonal CD8+ T cells and exhibit MHC-I upregulation, rimmed vacuoles, mitochondrial pathology, p62-positive inclusions, and nuclear clearance and cytoplasmic aggregation of TDP-43, resulting in expression of cryptic exons. Depletion of human T cells within IBM xenografts by treating mice intraperitoneally with anti-CD3 (OKT3) suppresses MHC-I upregulation, but rimmed vacuoles and loss of TDP-43 function persist. These data suggest that myofiber degeneration occurs independent of T cells, and muscle cell-intrinsic mechanisms, such as loss of TDP-43 splicing repression, drive IBM pathogenesis. One Sentence SummaryDepletion of T cells in a xenograft model of sporadic inclusion body myositis suppresses inflammation but not TDP-43 pathology or muscle degeneration.

pathology↗

bioRxiv2020

Human muscle stem cells are refractory to aging

Age-related loss of muscle mass and strength is widely attributed to limitation in the capacity of muscle resident satellite cells to perform their myogenic function. This idea contains two notions that have not been comprehensively evaluated by experiment. First, it entails the idea that we damage and lose substantial amounts of muscle in the course of our normal daily activities. Second, it suggests that mechanisms of muscle repair are in some way exhausted, thus limiting muscle regeneration. A third option is that the aged environment becomes inimical to the conduct of muscle regeneration. In the present study we used our established model of human muscle xenografting to test whether muscle samples taken from cadavers, of a range of ages, maintained their myogenic potential after being transplanted into immunodeficient mice. We find no measurable difference in regeneration across the range of ages investigated up to 78 years of age. Moreover, we report that satellite cells maintained their myogenic capacity even when muscles were grafted 11 days postmortem in our model. We conclude that the loss of muscle mass with increasing age is not attributable to any intrinsic loss of myogenicity and is most likely a reflection of progressive and detrimental changes in the muscle micro-environment such as to disfavor the myogenic function of these cells.

cell biology↗

bioRxiv2019

CaMKII oxidation is a performance/disease trade-off in vertebrate evolution

Reactive oxygen species (ROS) contribute to health and disease. CaMKII is a widely expressed enzyme whose activation by oxidation of regulatory domain methionines (ox-CaMKII) contributes to cardiovascular disease, asthma, and cancer. Here we integrate comparative genomic and experimental data to show that CaMKII activation by ROS arose more than half-a-billion years ago on the vertebrate stem lineage where it constituted a bridge between ROS and increased intracellular Ca2+ release, exercise responsive gene transcription, and improved performance in skeletal muscle. These enhancements to fight-or-flight physiology were likely key in facilitating a well-evidenced shift in the behavioural ecology of our immediate chordate ancestors, and, in turn, the evolutionary success of vertebrates. Still, the ox-CaMKII innovation for augmenting performance must be considered a critical evolutionary trade-off, as it rendered us more susceptible to common and often fatal diseases linked to excessive ROS.

evolutionary biology↗

bioRxiv2017

Reduced representation optical methylation mapping (R2OM2).

Reduced representation methylation analysis utilizes a subset of CpGs in order to report the overall methylation status of the probed genomic regions. Here, we use this concept in order to create fluorescent optical methylation profiles along chromosomal DNA molecules for epigenetic profiling. Reduced representation optical methylation mapping (R2OM2) in combination with Bionano Genomics next generation genome mapping (NGM) technology provides a hybrid genetic/epigenetic genome map of individual chromosome segments spanning hundreds of kilobase pairs (kbp). These long reads, along with the single-molecule resolution, allow for epigenetic variation calling and methylation analysis of large structural aberrations such as pathogenic macrosatellite arrays not accessible to single-cell next generation sequencing (NGS). We show that in addition to the inherent long-read benefits of R2OM2, it provides genomic methylation patterns comparable to whole genome bisulfite sequencing (WGBS) while retaining single-molecule information. The method is applied here to detect methylation along genes, around regulatory histone marks and to study facioscapulohumeral muscular dystrophy (FSHD), simultaneously recording the haplotype, copy number and methylation status of the disease-associated, highly repetitive locus onchromosome 4q.

genetics↗