Biology subjects

Merve, A.

Publications and source records attributed to Merve, A..

4 recordsLinked to original sources

bioRxiv2025

TDP-43 pathology induces CD8+ T cell activation through cryptic epitope recognition

Aggregation and nuclear depletion of the RNA binding protein TDP-43 are the crucial pathological features of amyotrophic lateral sclerosis (ALS) and inclusion body myositis (IBM), two degenerative diseases of the CNS and muscle. The loss of TDP-43 nuclear function results in the aberrant inclusion of cryptic exons in mRNA transcripts, leading to the expression of de novo proteins. Clonally expanded and highly differentiated CD8+ T cells have been observed in individuals with TDP-43 proteinopathies and therapeutics modulating the T cell response have recently been found to extend survival. However, the target antigens mediating T cell activation have remained elusive. Here, we investigate whether the de novo proteins induced by aberrant cryptic splicing due to TDP-43 nuclear loss can act as neo-antigens. We detect the HDGFL2 cryptic peptide and multiple other TDP-43 cryptic exons in IBM skeletal muscle, where their presence correlates with enrichment of T cells and class I antigen presentation pathways. Furthermore, we identify epitopes deriving from HDGFL2 and IGLON5 cryptic peptides which are recognized by clonally expanded and functionally differentiated populations of CD8+ T cells in ALS and IBM Patients. Finally, we demonstrate that T cells engineered to express the identified TCRs can bind and activate in response to the cryptic peptide derived epitopes (cryptic epitopes) and are able to kill TDP-43 deficient astrocytes. This work identifies for the first time specific T cell antigens in ALS and IBM, directly linking adaptive immune response to TDP-43 pathology.

immunology↗

bioRxiv2025

Spatial transcriptomic analysis of muscle biopsy from treatment-naive juvenile dermatomyositis patients reveals mitochondrial abnormalities despite disease-related interferon driven signature

ObjectivesThis study aimed to investigate the spatial transcriptomic landscape of muscle tissue from treatment-naive juvenile dermatomyositis (JDM) patients in comparison to healthy paediatric muscle tissue. MethodsMuscle biopsies from three JDM patients and three age-matched controls were analysed using the Nanostring GeoMx(R) Digital Spatial Profiler. Regions of interest were selected based on muscle fibres without immune cells, immune cell infiltration and CD68+ macrophage enrichment. Differential gene expression, pathway analysis and pathways clustering analysis were conducted. Key findings were validated in 19 cases of JDM using immunohistochemistry and chemical stains, and a bulk RNAseq dataset of four cases of JDM. ResultsJDM muscle tissues exhibited significant interferon pathway activation and mitochondrial dysfunction compared to controls. A 15-gene interferon signature was significantly elevated in JDM muscle and macrophage-enriched regions, correlating with clinical weakness. In contrast, mitochondrial dysregulation, characterized by downregulated respiratory chain pathways, was present regardless of interferon activity or muscle strength. The interferon-driven and mitochondrial signatures were replicated in an independent RNAseq dataset from JDM muscle; lack of association between interferon signature and mitochondrial dysregulation was validated in 19 cases by conventional staining methods. Clustering analysis revealed distinct transcriptomic profiles between JDM and control tissues, as well as between JDM patients with varying clinical phenotypes. ConclusionsThis study highlights mitochondrial dysfunction as a consistent pathological feature in JDM muscle, which may be independent of interferon-driven inflammation. These findings highlight the potential for mitochondrial-targeted therapies in JDM management and emphasise the need for further studies to explore their therapeutic value. KEY MESSAGESWhat is already known on this topic O_LIJuvenile dermatomyositis (JDM) involves interferon-driven inflammation and immune-mediated muscle damage. C_LIO_LIMitochondrial abnormalities in blood immune cells persist despite treatment and contribute to disease pathology. C_LI What this study adds O_LIMitochondrial dysfunction is present in both muscle fibres and tissue-infiltrating immune cells within JDM muscle. C_LIO_LIThese abnormalities are detectable even in clinically less severe muscle weakness. C_LIO_LIDegree of mitochondrial abnormality at transcript and protein level may be independent of strength of IFN-driven signal. C_LIO_LIMitochondrial dysregulation detected at transcriptional level correlates with abnormal transcription of muscle (sarcomere) and the subcellular peroxisome organelle. C_LI How this study might affect research, practice, or policy O_LITargeting mitochondrial dysfunction could enhance treatment outcomes for JDM, especially in patients whose disease is refractory to current therapies. C_LIO_LIInsights from this study support the development of stratification tools to detect aspects of pathology which are not tightly correlated with IFN-driven pathology. C_LI

immunology↗

bioRxiv2024

Modelling medulloblastoma pathogenesis and treatment in human cerebellar organoids.

Faithful genetically engineered in vivo models of medulloblastoma (MB) are currently available only for some molecular subgroups, in keeping with recent studies showing the unique role of human-specific progenitors in the development of G3 and G4 MB subgroups. We generated human cerebellar organoids (CbO) from expanded potential stem cells (EPSC) and characterised their epigenetic and transcriptomic profile compared to the developing human cerebellum. We show the presence of sub compartment-specific cerebellar lineages linked to MB formation, including populations expressing signature genes of putative G3 and G4 MB cells-of-origin. We show that these lineages can be genetically engineered to model MB tumour onset. Moreover, we demonstrate that CbO sustain proliferation and invasion of G3/4 MB cells in a 3D co-culture model (CbO-MB) while preserving their molecular identity, and that treatment of CbO-MB with anti-tumour compounds recapitulate the efficacy of in vivo drug testing in xenograft models.

cancer biology↗

bioRxiv2021

Biallelic loss-of-function OBSCN variants predispose individuals to severe, recurrent rhabdomyolysis

Rhabdomyolysis is the acute breakdown of skeletal myofibres in response to an initiating factor, most commonly toxins and over exertion. A variety of genetic disorders predispose to rhabdomyolysis through different pathogenic mechanisms, particularly in patients with recurrent episodes. However, the majority of cases remain without a genetic diagnosis. Here we present six patients who presented with severe and recurrent rhabdomyolysis, usually with onset in the teenage years; other features included a history of myalgia and muscle cramps. We identified ten bi-allelic loss-of-function variants in the gene encoding obscurin (OBSCN) co-segregating with disease. We show reduced expression of OBSCN and loss of obscurin protein in patient muscle. Obscurin is proposed to be involved in SR function and Ca2+ handling. Patient cultured myoblasts appear more susceptible to starvation as evidenced by a greater decreased in SR Ca2+ content compared to control myoblasts. This likely reflects a lower efficiency when pumping Ca2+ back into the SR and/or a decrease in Ca2+ SR storage ability when metabolism is diminished. OSBCN variants have previously been associated with cardiomyopathies. None of the patients presented with a cardiomyopathy and cardiac examinations were normal in all cases in which cardiac function was assessed. There was also no history of cardiomyopathy in first degree relatives, in particular in any of the carrier parents. This cohort is relatively young, thus follow-up studies and the identification of additional cases with bi-allelic null OBSCN variants will further delineate OBSCN-related disease and the clinical course of disease.

genetics↗