675P Understanding skeletal muscle pathology and function in late-onset Pompe disease: insights from proteomic and transcriptomic analyses

• Published in: Neuromuscular disorders : NMD Vol. 43; p. 104441
• Main Authors: Schaiter, A., Lohanadan, K., van der Ven, P., Hentschel, A., Mensch, A., Hahn, A., Kornblum, C., Stenzel, W., Krämer, H., Rosenbohm, A., Bartkuhn, M., Roos, A., Schänzer, A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2024
• ISSN: 0960-8966
• DOI: 10.1016/j.nmd.2024.07.742

Pompe disease is a metabolic lysosomal disease caused by mutations in the alpha 1,4-glucosidase (GAA) gene. Reduced GAA enzyme activity leads to accumulation of glycogen, particularly in striated muscle fibers. Dependent on the age of onset and residual GAA enzyme activity, Pompe disease is classified as infantile onset Pompe disease (IOPD) and late onset Pompe disease (LOPD). The clinical and morphological phenotype is highly variable and response to enzyme replacement therapy (ERT) can be difficult to predict. The aim of our study was to perform transcriptomic and proteomic studies on human skeletal muscle samples to obtain a deeper insight into the pathophysiological mechanisms underlying Pompe disease. In a retrospective study, mass spectrometry (MS) was performed on skeletal muscle biopsies from 21 LOPD patients (mean age 47.3y, 43% female) prior ERT and 11 non-diseased subjects (mean age 43.4y, 50% female). RNA-Seq analysis was conducted on 10 LOPD and 7 control samples. Samples with different degree of LOPD muscle pathology were included in the study and the muscle pathology was assessed by histological grading. Bioinformatic studies utilizing the GO and HALLMARK database, an overrepresentation pathway analysis and a gene set enrichment analysis were performed. Due to the large number of samples proteins associated with the degree of muscle pathology were identified by additional regression analysis. MS analysis identified a total of 830 proteins, and significant deregulation of 68 proteins in LOPD (44 downregulated and 24 upregulated proteins) compared to controls. RNA-Seq analysis revealed 20,171 genes, of which 22 showed significant down-regulation and 1 up-regulation in LOPD. Among others, sarcomere proteins associated with thin filaments (e.g. TPM3, TNNI2), thick filaments (e.g. MYL6B, MYH4), and z-discs (e.g. PDLIM3, NEB) were downregulated in LOPD. These findings were supported by transcriptomic analysis, which revealed that genes important for the structural integrity of the muscle fibers were systematically downregulated in LOPD. Correlation of MS data with the degree of muscle pathology unveiled a significant positive correlation of Vesicle-associated membrane associated protein B/C (VAPB), which is known to participate in the endoplasmic reticulum unfolded protein response (UPR), with increasing muscle pathology (p=0.024). Multiomic analysis of skeletal muscle biopsies from patients with LOPD revealed a significant deregulation of several proteins and genes involved in contractile muscle function. Whether these findings are dependent on intracellular glycogen accumulation needs to be investigated in further studies. In addition, the identification of proteins associated with the degree of muscle pathology may provide further insights into the clinical and morphological heterogeneity of LOPD.