bims-meglyc 2026-08-16 papers

bims-meglyc

Biomed News

on Metabolic disorders affecting glycosylation

Issue of 2026–08–16
six papers selected by
Silvia Radenkovic, UMC Utrecht

Proteo-Metabolomic Profiling of PMM2-CDG Reveals Dysregulation of Retinoic Acid Synthesis, Myo-Inositol, and the Hexosamine Pathway.
Crystal structure of a β1,3-Glucosyltransferase reveals an unusual substrate recognition by a two-domain GT-A fold glycosyltransferase.
CHARACTERIZATION OF A SERIES OF PATIENTS WITH GNE-RELATED THROMBOCYTOPENIA: INSIGHTS INTO PATHOGENESIS, DIAGNOSIS, AND TREATMENT.
Modeling Inherited Disorders of Post-Lanosterol Cholesterol Biosynthesis: From Animal Models to Patient-Derived Stem Cells.
Phenotypic and glycosylation profiles of the FGG c.902G > A (p.Arg301His) mutation in a Chinese pedigree with congenital dysfibrinogenemia.
Loss of MGAT3 Amplifies TGF-β Signaling to Promote Bronchiolitis Obliterans Progression.

J Inherit Metab Dis. 2026 Sep;49(5): e70233

Proteo-Metabolomic Profiling of PMM2-CDG Reveals Dysregulation of Retinoic Acid Synthesis, Myo-Inositol, and the Hexosamine Pathway.

Diana Gallego, Giuseppina Andreotti, Maria Monticelli, Debora Paris, Arturo Martín-Martínez, Alejandra Gámez, Mercedes Serrano, José Córdoba-Caballero, Pedro Seoane, Juan A G Ranea, Belén Pérez.

  Phosphomannomutase deficiency (PMM2-CDG), the most common congenital disorder of glycosylation (CDG), is characterized by multisystem involvement and a lack of disease-modifying therapies. While previous transcriptomic studies have uncovered disrupted cellular pathways, the functional consequences of these alterations remain poorly understood. To further investigate PMM2-CDG pathophysiology, we integrated proteomic and metabolomic profiling of patient-derived fibroblasts with previously published transcriptomic data. Proteomic analysis was performed using Tandem Mass Tag-based mass spectrometry, while metabolomics was conducted via Nuclear Magnetic Resonance spectroscopy. Multi-omics integration was performed using principal component analysis-based dimensionality reduction, incorporating clinical metadata as supplementary variables. Proteomic analysis identified 43 significantly altered proteins, with enrichment in the retinoic acid synthesis pathway, wound healing, and cytoskeletal organization. Metabolomic profiling revealed altered amino acid levels and elevated concentrations of UDP-GlcNAc, consistent with perturbation of the hexosamine biosynthesis pathway, and increased levels of myo-inositol. Notably, myo-inositol levels showed a strong association with disease severity in the integrated analysis. RT-qPCR confirmed the upregulation of GFPT2. This integrative multi-omics study identifies consistent alterations in the retinoic acid synthesis pathway and hexosamine biosynthesis in PMM2-CDG patient-derived fibroblasts and reveals an association between intracellular myo-inositol levels and disease severity. These findings provide new insights into PMM2-CDG-associated molecular alterations and illustrate the value of multi-omics integration for hypothesis generation in rare diseases.

Keywords:  PMM2‐CDG; hexosamine pathway; metabolomics; myo‐inositol; proteomics; retinoic acid; retinol

DOI:  https://doi.org/10.1002/jimd.70233
J Biol Chem. 2026 Aug 10. pii: S0021-9258(26)02290-8. [Epub ahead of print] 113418

Crystal structure of a β1,3-Glucosyltransferase reveals an unusual substrate recognition by a two-domain GT-A fold glycosyltransferase.

Steven J Berardinelli, Renuka Kadirvelraj, Kelvin B Luther, Zhongwei Gao, Digantkumar Chapla, Chin Huang, Daniel M Tehrani, Ao Zhang, Kelley W Moremen, Zachary A Wood, Robert S Haltiwanger.

  β1,3-Glucosyltransferase (B3GLCT) adds a glucose onto O-linked fucose on thrombospondin type 1 repeats (TSRs). Protein O-fucosyltransferase 2 (POFUT2) first transfers a fucose to properly folded TSRs containing a consensus sequence for O-fucosylation. This uncommon O-fucose modification is then extended to a glucose-fucose disaccharide by B3GLCT. B3GLCT is a GT-A fold glycosyltransferase and pathogenic variants cause Peters Plus Syndrome (PTRPLS, OMIM #261540), a Congenital Disorder of Glycosylation (CDG). Most GT-A fold family members have a single GT-A domain, but B3GLCT contains an additional GT-A domain. To assess the function of the additional GT-A domain and binding of TSR substrates, we determined the crystal structure of an O-fucosylated TSR (Fuc-O-TSR3) from Thrombospondin-1 bound to B3GLCT. The additional GT-A domain is essential for substrate binding but is catalytically inactive: it does not bind UDP or Mn2+ and is not a β1,3-glucosyltransferase. It also creates a deep pocket with a vestigial active site located on the opposite face of the Fuc-O-TSR3 substrate binding site. The Fuc-O-TSR3 acceptor substrate binds in a cleft between the two GT-A domains, each of which has evolved hypervariable regions for Fuc-O-TSR recognition. This structure is an unusual example of a glycosyltransferase with a catalytically inactive extra GT-A domain, providing insight into the binding of B3GLCT's diverse Fuc-O-TSR substrates. We also discuss how B3GLCT mimics the two-domain structure of GT-B fold glycosyltransferases. All GT-B fold glycosyltransferases contain two bilobal Rossmann-like fold domains, like B3GLCT. Our data also explains how PTRPLS-associated variants and predicted pathogenic mutations disrupt B3GLCT function.

Keywords:  Glycosyltransferase; O-fucosylation; Peters Plus Syndrome; Thrombospondin Type 1 Repeats; X-ray Crystallography

DOI:  https://doi.org/10.1016/j.jbc.2026.113418
J Thromb Haemost. 2026 Aug 14. pii: S1538-7836(26)00526-X. [Epub ahead of print]

CHARACTERIZATION OF A SERIES OF PATIENTS WITH GNE-RELATED THROMBOCYTOPENIA: INSIGHTS INTO PATHOGENESIS, DIAGNOSIS, AND TREATMENT.

Serena Barozzi, Christian A Di Buduo, Stefania Zampieri, Federica Isidori, Simone Frisari, Giuseppe Lassandro, Marco Lunghi, Alice Martinotti, Valeria Bozzi, Tommaso Mina, Simone Cesaro, Tommaso Pippucci, Paola Giordano, Alessandra Balduini, Alessandro Pecci.

   BACKGROUND: GNE-related thrombocytopenia (GNE-RT) is a very rare disorder caused by biallelic variants in GNE, encoding a key enzyme for the sialic acids biosynthesis. Patients usually present severe thrombocytopenia and excessive bleeding. Knowledge about this condition is still poor. There are no recognized tools for diagnosis. Previous study of one patient showed reduced platelet half-life as a mechanism of thrombocytopenia; however, it is still unclear if the sialylation defect also impairs platelet biogenesis.
OBJECTIVES: To gain insights into clinical aspects and platelet biogenesis in GNE-RT.
METHODS: We investigated 4 novel GNE-RT patients (3 families). A recently standardized flow cytometry assay was applied to characterize platelet sialylation. Patients' megakaryocytes were cultured to study megakaryopoiesis and proplatelet formation. A validated three-dimensional bone marrow model was exploited to investigate platelet production.
RESULTS: We characterized 3 novel GNE variants, demonstrating the pathogenicity of 2 VUS. In all individuals, platelet flow cytometry detected an obvious increase in RCA-1 and ECL lectins binding and decreased MAL-II binding. Sialylation of serum transferrin did not show straightforward alterations. Although presenting the sialylation defect, patients' megakaryocytes showed preserved differentiation, maturation, and proplatelet formation. Megakaryocytes generated ex-vivo a normal number of normal-sized platelets. Two patients received Eltrombopag, achieving a durable clinical response (38- and 72-month follow-up).
CONCLUSIONS: The profound megakaryocyte sialylation defect induced by GNE variants does not affect platelet biogenesis. Platelet flow cytometry for RCA-1 and MAL-II binding is a reliable and simple assay for diagnosis of GNE-RT. Based on literature review, 55% of GNE-RT patients responded to thrombopoietin-mimetics.

Keywords:  GNE gene; inherited thrombocytopenia; platelet biogenesis; protein glycosylation; sialic acids

DOI:  https://doi.org/10.1016/j.jtha.2026.08.004
Int J Mol Sci. 2026 Jul 30. pii: 6853. [Epub ahead of print]27(15):

Modeling Inherited Disorders of Post-Lanosterol Cholesterol Biosynthesis: From Animal Models to Patient-Derived Stem Cells.

Elvira Akhmetzyanova, Evelina Nasybullina, Albert Rizvanov, Yana Mukhamedshina.

  Altered post-lanosterol cholesterol biosynthesis causes a heterogeneous group of rare inherited metabolic disorders, including Smith-Lemli-Opitz syndrome, desmosterolosis, lathosterolosis, and congenital hemidysplasia with ichthyosiform nevus and limb defects syndrome. These conditions are characterized by impaired cholesterol synthesis together with the accumulation of disease-specific sterol intermediates. Current experimental and clinical evidence suggests that pathogenesis reflects both cholesterol insufficiency and sterol-mediated toxicity, including oxidative stress, perturbed developmental signaling, membrane dysfunction, and impaired neurodevelopment. Experimental models have played a central role in elucidating these mechanisms and in evaluating emerging therapeutic strategies. This review provides a comprehensive overview of currently available experimental models used to investigate inherited cholesterol biosynthesis disorders, including genetically engineered animal models, patient-derived fibroblasts, immortalized and CRISPR/Cas9-edited cell lines, and induced pluripotent stem cell-based systems. Particular emphasis is placed on Smith-Lemli-Opitz syndrome, the most extensively studied disorder within this group, while recent advances in modeling desmosterolosis, lathosterolosis, and congenital hemidysplasia with ichthyosiform nevus and limb defects syndrome are also critically discussed. We compare the strengths and limitations of each experimental platform, highlighting their contributions to understanding sterol metabolism, developmental abnormalities, and cell-type-specific disease mechanisms. Finally, we discuss current challenges and future perspectives, including the development of patient-specific induced pluripotent stem cell models, genome editing approaches, and next-generation multicellular systems. Collectively, this review provides an updated framework for selecting appropriate experimental models to investigate cholesterol biosynthesis disorders and accelerate the development of mechanism-based therapeutic strategies.

Keywords:  CHILD syndrome; CRISPR/Cas9; DHCR24; DHCR7; NSDHL; SC5D; Smith–Lemli–Opitz syndrome; animal models; cholesterol biosynthesis; desmosterolosis; iPSCs; lathosterolosis; patient-derived fibroblasts

DOI:  https://doi.org/10.3390/ijms27156853
Thromb Res. 2026 Aug 01. pii: S0049-3848(26)00212-4. [Epub ahead of print]264 109793

Phenotypic and glycosylation profiles of the FGG c.902G > A (p.Arg301His) mutation in a Chinese pedigree with congenital dysfibrinogenemia.

Xiaozhen Kang, Luoyuan Cao, Weitong Peng, Xianxiang Peng, Jiaojiao Lu, Tao Zhang, Shouzhong Wei.

   OBJECTIVE: Congenital dysfibrinogenemia (CD) is characterized by functionally impaired fibrinogen. This study aimed to characterize the phenotypic, molecular, and clinical features associated with the FGG p.Arg301His mutation in a Chinese pedigree.
METHODS: A Chinese pedigree comprising 12 members was enrolled, including 6 individuals carrying the FGG p.Arg301His mutation. Phenotypic evaluation was performed using conventional coagulation tests, thromboelastography (TEG), and thrombosis biomarker panels. Fibrinogen was purified from plasma and subjected to structural analysis via SDS-PAGE and LC-MS/MS mass spectrometry. Glycosylation profiles of the fibrinogen γ-chain were compared between mutation carriers and healthy controls. Molecular modeling was conducted to predict the structural effects of the mutation.
RESULTS: Conventional coagulation tests combined with TEG effectively identified a hypocoagulable state in mutation carriers, whereas thrombosis biomarker panels showed limited diagnostic value. Structural analysis revealed markedly increased O-glycosylation sites (17 vs. 3) and N-glycosylated peptides (5 vs. 3) in the fibrinogen γ-chain of mutation carriers compared with controls. A unique glycan HexNAc(6)Hex(4)Fuc(2) was detected exclusively in the mutation group. Bioinformatic modeling predicted that the p.Arg301His substitution reduces hydrogen bonding, leading to conformational destabilization (ΔΔG ranging from -0.08 to -1.211 kcal/mol.). Clinically, female carriers experienced miscarriage and postpartum hemorrhage, while male carriers remained asymptomatic.
CONCLUSION: The FGG p.Arg301His mutation induces aberrant glycosylation and structural alterations in fibrinogen, contributing to functional impairment and a hypocoagulable state. These molecular changes may underlie the obstetric complications observed in female carriers. Integration of genetic, functional, glycosylation, and conformational analyses is of great significance for accurate assessment of bleeding and obstetric complication risks in patients with CD.

Keywords:  Congenital dysfibrinogenemia; Glycosylation; Mass spectrometry; Molecular modeling; Thromboelastography

DOI:  https://doi.org/10.1016/j.thromres.2026.109793
Clin Lab. 2026 Aug 01. 72(8):

Loss of MGAT3 Amplifies TGF-β Signaling to Promote Bronchiolitis Obliterans Progression.

Wei Ge, Jing Li, Yan Chen, Daxiong Zeng, Shuang Yang, Junhong Jiang.

BACKGROUND: Bronchiolitis obliterans syndrome (BOS), a severe complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT), presents as chronic graft-versus-host disease characterized by inflammation and fibrosis of the small airway epithelium. This progressive fibrosis obstructs bronchiolar airways, leading to respiratory distress in patients. Due to the lack of effective treatments, a deeper understanding of the underlying mechanisms is crucial. This study explored the molecular mechanisms underlying the abnormal glycosylation regulation in BOS, aiming to provide new insights for early diagnosis and treatment of this disease.
METHODS: Bronchoalveolar lavage fluid (BALF) was collected from patients with and without BOS following allo-HSCT. N-glycans from the BALF were enriched using a solid-phase extraction method. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF-MS) was used to detect N-glycosylation characteristics in the BALF of BOS patients. This phenomenon was validated using a graft-versus-host disease (GVHD) mouse model. The impact of MGAT3 knockdown on the biological functions of airway epithelial cells (BEAS-2B) was then examined using lentivirus transfection. The molecular mechanism by which the loss of MGAT3 enhances TGF-β signaling was explored using western blotting, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence (IF).
RESULTS: Our study investigated N-glycosylation changes in BALF of BOS patients and identified a strong correlation between the loss of bisecting-GlcNAc N-glycans and BOS progression. We found a novel mechanism where MGAT3, the enzyme synthesizing bisecting-GlcNAc structures, critically regulates TGF-β signaling. MGAT3 and bisecting-GlcNAc deficiency significantly enhance TGF-β signaling by increasing TGF-β storage through upregu-lation of latent TGF-β binding protein 1 (LTBP1) and by increasing the availability of TGF-β receptors.
CONCLUSIONS: Our discovery highlights the crucial role of aberrant glycosylation in BOS progression and holds significant promise for developing novel biomarkers for early diagnosis, identifying new therapeutic targets, and ultimately improving the quality of life for BOS patients.

DOI: https://doi.org/10.7754/Clin.Lab.2025.250831