Gutierrez-Cruz, G. | Search bioRxiv

bioRxiv2022

Transcriptomic profiling reveals distinct subsets of immune checkpoint inhibitor-induced myositis

ObjectivesInflammatory myopathy or myositis is a heterogeneous family of immune-mediated diseases including dermatomyositis (DM), antisynthetase syndrome (AS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM). Immune checkpoint inhibitors (ICI) can also cause myositis (ICI-myositis). This study was designed to define gene expression patterns in muscle biopsies from patients with ICI-myositis. MethodsBulk RNA sequencing was performed on 200 muscle biopsies (35 ICI-myositis, 44 DM, 18 AS, 54 IMNM, 16 IBM, and 33 normal muscle biopsies) and single nuclei RNA sequencing was performed on 22 muscle biopsies (7 ICI-myositis, 4 DM, 3 AS, 6 IMNM, and 2 IBM). ResultsUnsupervised clustering defined three distinct transcriptomic subsets of ICI-myositis: ICI-DM, ICI-MYO1, and ICI-MYO2. ICI-DM included patients with DM and anti-TIF1{gamma} autoantibodies who, like DM patients, overexpressed type 1 interferon-inducible genes. ICI-MYO1 patients had highly inflammatory muscle biopsies and included all patients that developed co-existing myocarditis. ICI-MYO2 was composed of patients with predominant necrotizing pathology and low levels of muscle inflammation. The type 2 interferon pathway was activated both in ICI-DM and ICI-MYO1. Unlike the other types of myositis, all three subsets of ICI-myositis patients overexpressed genes involved in the IL6 pathway. ConclusionsWe identified three distinct types of ICI-myositis based on transcriptomic analyses. The IL6 pathway was overexpressed in all groups, the type I interferon pathway activation was specific for ICI-DM, the type 2 IFN pathway was overexpressed in both ICIDM and ICI-MYO1, and only ICI-MYO1 patients developed myocarditis.

immunology↗

bioRxiv2021

Transcriptomic analysis of mdx mouse muscles reveals a signature of early human Duchenne muscular dystrophy

The mdx mouse (C57BL/10ScSn-DMDmdx/J) is the oldest model of Duchenne muscular dystrophy (DMD). Mdx remains popular and has not been replaced by newer mouse models, despite criticisms that mdx has a nearly normal lifespan and mild pathology while DMD remains a severe, fatal disease. At some point we noticed that the absence of mdx RNA-seq data limited our ability to assess the results of physiological work on the mouse model and to compare these results to human genetic data [1]. We carried out RNA-seq analysis of wild-type and mdx mice of 2 and 5 months of age, using three hindlimb muscles per mouse: the flexor digitorum brevis (FDB), the extensor digitorum longus (EDL) and the soleus (SOL), with a total of 55 samples. We then mined the data and found that each of the three muscles is a valid experimental model for DMD-related mouse work, even the FDB, despite a delayed pathology development. We also show that the mdx mouse muscles are enriched in metabolic, developmental, regenerational and structural pathways that have been found to be the "disease signature" of DMD in young and presymptomatic subjects [38, 39]. Additionally, we show that healthy human muscle fiber microtubules present the grid-like organization found in control rodents but perturbed in the mdx mouse. We conclude that the mdx mouse appropriately mimics the early stages of DMD, with its microtubule defects signaling fiber regeneration [35]. We hope that these results may contribute to a better understanding of the failure of regeneration as DMD progresses.

genetics↗