PGM1-congenital disorder of glycosylation (PGM1-CDG) is frequently associated with cardiomyopathy. Although galactose therapy corrects glycosylation defects, cardiac dysfunction typically persists, suggesting a glycosylation-independent mechanism. Recent evidence of mitochondrial abnormalities in PGM1-deficient human and murine heart, together with the association of PGM1 with the Z-disk protein LDB3 (ZASP/Cypher), suggests a critical role for PGM1 in cardiomyocyte structural and energetic homeostasis. We hypothesized that PGM1-related cardiomyopathy arises from a glycosylation-independent disruption of Z-disk-mitochondrial coupling driven by loss of PGM1-LDB3 interactions, resulting in mitochondrial energy failure and impaired contractile function. Induced pluripotent stem cell-derived cardiomyocytes (iCMs) were generated from PGM1-deficient patient fibroblasts. Multielectrode array (MEA) recordings, untargeted (glyco)proteomics, and pathway analysis were performed to assess functional and molecular changes. Key findings were validated using tracer metabolomics and mitochondrial respiration assays. PGM1-deficient iCMs exhibited reduced beating frequency, impaired contractility, and prolonged contraction kinetics. Proteomic analyses revealed depletion of Z-disk components, including LDB3. AlphaFold3 structural modeling predicted a direct interaction between PGM1 and LDB3, implicating PGM1 in Z-disk integrity, which was confirmed in vitro. In addition, mitochondrial proteins were severely depleted, prompting us to investigate mitochondrial function. Functional validation confirmed extensive metabolic rewiring, energy depletion, and severely impaired mitochondrial respiration. Finally, the in silico drug repurposing identified possible therapeutic options that could target PGM1-deficient cardiomyopathy. Our data suggests PGM1 is key regulator of cardiomyocyte function, linking sarcomeric Z-disk integrity with mitochondrial metabolism. These mechanistic insights offer a foundation for developing targeted therapies for PGM1-CDG and potentially other cardiomyopathies involving Z-disk dysfunction.

Congenital disorders of glycosylation (CDG) are rare inherited disorders resulting from defects in cellular glycosylation machinery. Albumin has recently been shown to be N-glycosylated at two non-canonical glycosylation sites. We applied multiplexed mass spectrometry-based glycoproteomics to identify site-specific N-glycosylation alterations in albumin from patients with PMM2-CDG, MPI-CDG, SRD5A3-CDG, MAN1B1-CDG and PGM1-CDG. Our findings demonstrate that the glycosylation of albumin is indeed affected in CDG and indicate a potential role for albumin-derived glycopeptides as diagnostic biomarkers.

Protein glycosylation is a crucial process involving the addition of oligosaccharides to proteins, which plays a significant role in stabilizing proteins and mediating protein-protein interactions. Mutations in genes associated with glycosylation can lead to congenital disorders of glycosylation (CDG), resulting in multisystem disorders. One such example is phosphoglucomutase 1 (PGM1) -CDG, caused by a deficiency of the PGM1 enzyme. In this report, we describe a patient with PGM1-CDG who was initially misdiagnosed with growth hormone insensitivity and benefited from recombinant human insulin-like growth factor-1 (rhIGF-1) therapy. A 2-year-11-month-old female patient, born to first-degree cousin parents, presented with hypoglycemia and short stature. Her physical examination revealed frontal bossing, infantile facial appearance, and short stature. Laboratory investigations revealed that basal and stimulated growth hormone levels were very high, IGF-1 was low, and the inadequate response to the IGF generation test was consistent with growth hormone insensitivity (GHI). The patient was started on rhIGF-1 therapy, resulting in significant height gain. Subsequently, the patient showed improvement in height with rhIGF-1 therapy. The patient, who had additional findings such as elevated creatine kinase (CK) and transaminase levels and cardiomyopathy, was diagnosed with PGM1-CDG. This case highlights that PGM1-CDG can mimic clinical and laboratory findings of GHI. CDG diagnosis should be considered in cases with clinical and laboratory findings of GHI accompanied by multisystem disorders such as hepatopathy, elevated CK, and cardiomyopathy. This patient's successful response to rhIGF-1 therapy highlights the potential benefits of targeted therapies in treating growth hormone-related disorders in patients.

Atrial septal defect (ASD) is a common congenital heart defect that remains mainly asymptomatic in childhood. However, when left ventricular (LV) compliance is impaired, as in myocarditis or cardiomyopathy, ASD may lead to severe heart failure due to increased left-to-right shunting and a reduced systemic cardiac output. We report the case of a 6-year-old boy with CDG-PGM1 and a large ASD who developed acute refractory heart failure, likely triggered by Parvovirus B19 myocarditis. Despite optimal medical therapy, including immunoglobulins, inotropes, and heart failure medication, he remained dependent on pharmacological support. He was deemed ineligible for heart transplantation due to his underlying metabolic condition; therefore an ASD closure was questioned as a last therapeutic option. A balloon occlusion test showed a mild increase in LV end-diastolic pressure, allowing percutaneous closure using a hand-made fenestrated device. The procedure was successful, leading to rapid weaning from inotropes and full clinical recovery. At 6-month follow-up, LV function was normalized, and the patient was asymptomatic. In selected patients with impaired LV compliance, ASD closure may offer a life-saving therapeutic option. Haemodynamic evaluation with balloon occlusion testing is essential to evaluate closure feasibility and determine the potential need of using a fenestrated device.

The ability of adeno-associated viruses (AAVs) to transduce host cells relies on interactions with glycan moieties on the cellular surface. Consequently, disrupted protein glycosylation, which is seen in a range of neurodevelopmental and neurodegenerative diseases, could impair transduction efficiency. Understanding how altered glycosylation impacts AAV binding is essential to optimize AAV-mediated therapeutic strategies. We used glycoproteomics data from cortical brain organoids and iCardiomyocytes of individuals with congenital disorders of glycosylation (CDG) (ALG13-, PMM2-, and PGM1-CDG) to examine the abundance of AAV-binding glycan species. Additionally, we assessed the abundance of coreceptors in proteomics data. We found that the abundance of AAV-binding glycan species was downregulated for all CDG subtypes, but this was significant only for AAV5-, AAV8-, and AAV9-binding glycan motifs in PGM1-CDG. The proteomics data showed significantly decreased abundance of the coreceptor PDGFRβ in ALG13-CDG. The downregulation of glycan species and AAV coreceptors in models of aberrant protein glycosylation underscores the need to optimize AAV selection for conditions with altered protein glycosylation, including CDG and neurodegenerative diseases such as Parkinson's and Alzheimer's disease.