bims-meglyc 2025-02-16 papers

bims-meglyc

Biomed News

on Metabolic disorders affecting glycosylation

Issue of 2025–02–16
eight papers selected by
Silvia Radenkovic, UMC Utrecht

Mass Spectrometry as a First-Line Diagnostic Aid for Congenital Disorders of Glycosylation.
Biochemical testing for congenital disorders of glycosylation: A technical standard of the American College of Medical Genetics and Genomics (ACMG).
Causes of mortality in the congenital disorders of glycosylation.
Identification of CNTN2 as a genetic modifier of PIGA-CDG in a family with incomplete penetrance and in Drosophila.
C1GALT1C1-Associated Mosaic Disorder of Glycosylation in a Female.
Improvement of Motor Function in SLC39A8-Related Ataxia Through Manganese Supplementation: A Therapeutic Insight.
A biallelic variant in GORASP1 causes a novel Golgipathy with glycosylation and mitotic defects.
Integrated proteomics and N-glycoproteomic characterization of glioblastoma multiform revealed N-glycosylation heterogeneities as well as alterations in sialyation and fucosylation.

Mass Spectrom (Tokyo). 2025 ;14(1): A0169

Mass Spectrometry as a First-Line Diagnostic Aid for Congenital Disorders of Glycosylation.

Yoshinao Wada.

  Congenital disorders of glycosylation (CDG) constitute a group of rare inherited metabolic disorders resulting from mutations in genes involved in the biosynthesis of glycan chains that are covalently attached to proteins or lipids. To date, nearly 200 genes have been identified as responsible for these disorders, with approximately half implicated in N-glycosylation defects. Diagnosis of CDG is primarily achieved through genetic analysis and the identification of glycan abnormalities, referred to as molecular phenotypes. With the increasing use of whole exome and genome sequencing in the investigation of diseases with unknown etiology, the number of cases suspected of CDG is increasing, highlighting the necessity for glycan analysis. Molecular phenotyping in CDG typically targets glycoproteins, with transferrin and apolipoprotein CIII being key representatives of N- and mucin-type O-glycosylation, respectively. Mass spectrometry (MS) provides rapid analysis and yields moderately detailed information, establishing it as a first-line molecular diagnostic tool that complements genetic analysis. Structural anomalies detected by MS can be classified into distinct patterns, which may indicate specific defects within the glycosylation pathway. In cases of CDG types that lack clear molecular phenotypes, characteristic metabolites can often be identified and quantified by MS, further aiding in the diagnostic process. Molecular diagnosis of CDG using MS can be performed with a standard mass spectrometer and a dried blood spot on filter paper, enabling its application in population-based mass screening.

Keywords:  apolipoprotein CIII; congenital disorders of glycosylation; diagnosis; mass screening; transferrin

DOI:  https://doi.org/10.5702/massspectrometry.A0169
Genet Med. 2025 Feb 13. pii: S1098-3600(24)00262-4. [Epub ahead of print] 101328

Biochemical testing for congenital disorders of glycosylation: A technical standard of the American College of Medical Genetics and Genomics (ACMG).

Patricia L Hall, Christina Lam, Lynne Wolfe, Andrew Edmondson, Acmg Laboratory Quality Assurance Committee.

  Congenital disorders of glycosylation (CDG) are a large and continually expanding group of disorders that present with a variety of clinical findings and have been linked to over 170 genes. Individually, CDGs are rare; however, the true incidence may be underestimated because of the variability of the clinical findings, and the multiple testing strategies needed to diagnosis them across multiple pathways. Testing for CDGs has evolved over recent years with the availability of high-throughput molecular testing and improved gene discovery techniques. Biochemical testing to detect defects in glycosylated proteins or enzymatic deficiency still plays a critical role in the diagnosis of affected individuals, and both testing modalities are often required to finalize a diagnosis. Emerging therapeutic approaches targeting improvements in glycosylation require reliable and reproducible biochemical testing for therapeutic monitoring, dose adjustment, and avoidance of dose-related side effects. To maintain clinical sensitivity and specificity and to ensure reproducibility across laboratories performing complex biochemical testing, the American College of Medical Genetics and Genomics has developed the following technical standard.

Keywords:  Carbohydrate-deficient transferrin; Congenital disorders of glycosylation; Glycan profiling; Glycosylation defect

DOI:  https://doi.org/10.1016/j.gim.2024.101328
Mol Genet Metab. 2025 Feb 04. pii: S1096-7192(25)00043-5. [Epub ahead of print]144(3): 109052

Causes of mortality in the congenital disorders of glycosylation.

Hana Alharbi, Seishu Horikoshi, Sabrina Malone Jenkins, Fernando Scaglia, Christina Lam, Eva Morava, Austin Larson, Andrew C Edmondson.

  Congenital Disorders of Glycosylation (CDG) are a group of some 200 genetic disorders with PMM2-CDG being the most common disease. These disorders individually remain rare with poorly understood natural history (NH) and causes of mortality. We established a NH study for CDG and collected both prospective and retrospective data on CDG outcomes. In the current data set analysis on deceased patients, we describe the clinical phenotype and causes of death for thirty-seven individuals with various genetic causes of CDG. About a third of this cohort were affected with PMM2-CDG. All of the patients presented with multisystem features with involvement of the neurological system. The majority of patients involved in this study died during the first three years of life, and only four patients lived beyond ten years. The cause of death was unavailable for two patients, and about a third died secondary to cardiopulmonary failure. Progression of neurological involvement, sepsis and respiratory infection were also among the reported causes. Pericardial effusion was the primary cause of death for three infants affected with PMM2-CDG. This study emphasizes the importance of diagnosis and supportive care following the published monitoring and management guidelines for affected patients with CDG to optimize their health and development in the early stages of the disease.

Keywords:  ALG6-CDG; CDG; Congenital disorder(s) of glycosylation; Mortality; N-linked glycosylation; O-linked glycosylation; PMM2-CDG

DOI:  https://doi.org/10.1016/j.ymgme.2025.109052
Am J Hum Genet. 2025 Feb 05. pii: S0002-9297(25)00017-5. [Epub ahead of print]

Identification of CNTN2 as a genetic modifier of PIGA-CDG in a family with incomplete penetrance and in Drosophila.

Holly J Thorpe, Brent S Pedersen, Miranda Dietze, Nichole Link, Aaron R Quinlan, Joshua L Bonkowsky, Ashley Thomas, Clement Y Chow.

  Loss-of-function mutations in the X chromosome gene PIGA lead to phosphatidylinositol glycan class A congenital disorder of glycosylation (PIGA-CDG), an ultra-rare CDG typically presenting with seizures, hypotonia, and neurodevelopmental delay. We identified two brothers (probands) with PIGA-CDG, presenting with epilepsy and mild developmental delay. Both probands carry PIGA c.395C>G (p.Ser132Cys), an ultra-rare variant predicted to be damaging. Strikingly, the maternal grandfather and a great uncle also carry the same PIGA variant, but neither presents with symptoms associated with PIGA-CDG. We hypothesized that genetic modifiers might contribute to this reduced penetrance. Using whole-genome sequencing and pedigree analysis, we identified possible susceptibility variants found in the probands and not in the carriers and possible protective variants found in the carriers and not in the probands. Candidate genetic modifier variants included heterozygous, damaging variants in three genes involved directly in glycosylphosphatidylinositol (GPI)-anchor biosynthesis and additional variants in other glycosylation pathways or encoding GPI-anchored proteins. Using a Drosophila eye-based model, we tested modifiers identified through genome sequencing. Loss of CNTN2, a predicted protective modifier that encodes a GPI-anchored protein responsible for neuron/glial interactions, rescues loss of PIGA in the eye-based model, as we predict in the family. Further testing found that the loss of CNTN2 also rescues PIGA-CDG-specific phenotypes, including seizures and climbing defects in Drosophila neurological models of PIGA-CDG. Using pedigree information, genome sequencing, and in vivo testing, we identified CNTN2 as a strong candidate modifier that could explain the incomplete penetrance in this family. Identifying and studying rare disease modifier genes in families may lead to therapeutic targets.

Keywords:  Drosophila; GPI-anchor synthesis; PIGA; congenital disorders of glycosylation; genetic modifier; incomplete penetrance

DOI:  https://doi.org/10.1016/j.ajhg.2025.01.017
J Inherit Metab Dis. 2025 Mar;48(2): e70006

C1GALT1C1-Associated Mosaic Disorder of Glycosylation in a Female.

Rajindra P Aryal, Aditya Ramanujan, Camille Bucci, Christian Neckelmann, Jamie Heimburg-Molinaro, Sandra F Cummings, Florian Erger, Bodo B Beck, Laurie H Seaver, Richard D Cummings.

  Cosmc, encoded by the X-linked C1GALT1C1, is a molecular chaperone in the endoplasmic reticulum and a master regulator of O-glycosylation of mammalian glycoproteins. Recently, we described a germline mutation in C1GALT1C1 in two male patients, giving rise to a congenital disorder of glycosylation-COSMC-CDG. Here, we have identified a female patient with a de novo mosaic variant in C1GALT1C1 (c.202C>T, p.Arg68*), which results in a truncated and nonfunctional form of Cosmc (Cosmc-R68). The patient is mosaic, as ~27% of her buccal cells carry the mutation. The patient is now a 5-year old who presented with nonimmune hydrops fetalis. As Cosmc is essential for the generation of normal O-glycans through regulating T-synthase activity, thereby enabling the formation of the universal Core 1 O-glycan Galβ1-3GalNAcα1-Ser/Thr (T-antigen), the loss of Cosmc leads to the expression of the unusual precursor O-glycan termed Tn-antigen (CD175) (GalNAcα1-Ser/Thr). Owing to the mutational mosaicism, only a significant minority of cells would exhibit abnormal O-glycosylation. Analysis of red blood cells (RBCs), leukocytes, and serum from this patient indicated reduced expression of Cosmc and T-synthase proteins and lower T-synthase activity. Consistent with these findings, we observed reduced normal O-glycans in serum glycoproteins and RBCs from the patient, along with elevated expression of the Tn-antigen in serum glycoproteins compared to controls. This case represents the first description of a true mosaic loss-of-function variant in C1GALT1C1, that is, one that occurred postzygotically during embryogenesis, and raises interesting questions about the role of O-glycosylation during fetal development and its consequences on the clinical presentation.

Keywords:  Cosmc; O‐glycosylation; Tn‐antigen; acquired disorder of glycosylation; glycoprotein; mosaic

DOI:  https://doi.org/10.1002/jimd.70006
Mov Disord Clin Pract. 2025 Feb 09.

Improvement of Motor Function in SLC39A8-Related Ataxia Through Manganese Supplementation: A Therapeutic Insight.

Denise Maria Meneses Cury Portela, Thiago Gonçalves Guimarães, Sandra Tuany Alves de Morais, Natália Rebeca Alves de Araújo, Luana Larisse de Sousa Araújo, Vinicius Santana Vasconcelos, Gustavo Sousa Noleto, Patricia Maria da Costa Braga, Sarah Teixeira Camargos.



Keywords:  SLC39A8; cerebellar ataxia; congenital disorder of glycosylation; manganese

DOI:  https://doi.org/10.1002/mdc3.70001
Life Sci Alliance. 2025 Apr;pii: e202403065. [Epub ahead of print]8(4):

A biallelic variant in GORASP1 causes a novel Golgipathy with glycosylation and mitotic defects.

Sophie Lebon, Arnaud Bruneel, Séverine Drunat, Alexandra Albert, Zsolt Csaba, Monique Elmaleh, Alexandra Ntorkou, Yann Ténier, François Fenaille, Pierre Gressens, Sandrine Passemard, Odile Boespflug-Tanguy, Imen Dorboz, Vincent El Ghouzzi.

GRASP65 is a Golgi-associated peripheral protein encoded by the GORASP1 gene and required for Golgi cisternal stacking in vitro. A key role of GRASP65 in the regulation of cell division has also been suggested. However, depletion of GRASP65 in mice has little effect on the Golgi structure and the gene has not been associated with any human phenotype to date. Here, we report the identification of the first human pathogenic variant of GORASP1 (c.1170_1171del; p.Asp390Glufs*18) in a patient combining a neurodevelopmental disorder with neurosensory, neuromuscular, and skeletal abnormalities. Functional analysis revealed that the variant leads to a total absence of GRASP65. The structure of the Golgi apparatus did not show fragmentation, but glycosylation anomalies such as hyposialylation were detected. Mitosis analyses revealed an excess of prometaphases and metaphases with polar chromosomes, suggesting a delay in the cell cycle. These phenotypes were recapitulated in RPE cells in which a similar mutation was introduced by CRISPR/Cas9. These results indicate that loss of GRASP65 in humans causes a novel Golgipathy associated with defects in glycosylation and mitotic progression.

DOI: https://doi.org/10.26508/lsa.202403065
Clin Proteomics. 2025 Feb 08. 22(1): 6

Integrated proteomics and N-glycoproteomic characterization of glioblastoma multiform revealed N-glycosylation heterogeneities as well as alterations in sialyation and fucosylation.

Mingjun Hu, Kaiyue Xu, Ge Yang, Bo Yan, Qianqian Yang, Liang Wang, Shisheng Sun, Huijuan Wang.

   BACKGROUND: Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor. Notwithstanding tremendous efforts having been put in multi-omics research to profile the dysregulated molecular mechanisms and cellular pathways, there is still a lack of understanding about the glycoproteomic of GBM. Glycosylation as one of the most important post-translational modifications is crucial in regulating cell proliferation and relevant oncogenic pathways.
RESULTS: In the study, we systematically profiled N-glycoproteomics of para-cancerous and cancerous tissues from GBM patients to reveal the site-specific N-glycosylation pattern defined by intact glycopeptides. We identified and quantified 1863 distinct intact glycopeptides (IGPs) with 161 N-linked glycan compositions and 326 glycosites. There were 396 IGPs from 43 glycoproteins differed between adjacent tissues and GBM. Then, proteomic and glycoproteomic data were combined, and the normalized glycosylation alteration was calculated to determine whether the difference was attributed to the global protein levels or glycosylation. The altered glycosylation triggered by site-specific N-glycans and glycoprotein abundance, as well as glycosite heterogeneity, were demonstrated. Ultimately, an examination of the overall glycosylation levels revealed a positive contribution of sialylated or/and fucosylated glycans.
CONCLUSIONS: Overall, the dataset highlighted molecular complexity and distinct profiling at translational and post-translational levels, providing valuable information for novel therapeutic approaches and specific detection strategies.

Keywords:   N-glycan; N-glycosylation heterogeneities; Glioblastoma multiform; Intact glycopeptides; Proteomics

DOI:  https://doi.org/10.1186/s12014-025-09525-9