bims-meglyc 2025-08-17 papers

bims-meglyc

Biomed News

on Metabolic disorders affecting glycosylation

Issue of 2025–08–17
seven papers selected by
Silvia Radenkovic, UMC Utrecht

NGLY1-CDDG: report of two cases from India and brief review of literature.
Are viral vector-mediated therapies compatible with aberrant glycosylation?
ALG13 loss-of-function alters glycosylation, impairs neuronal maturation, and drives network hypoactivity in a cortical organoid model of CDG.
The glycosyltransferase ALG3 is an AKT substrate that regulates protein N-glycosylation.
Laboratory diagnosis of congenital and acquired coagulopathies, including challenging-to-diagnose rare bleeding disorders.
Functional Characterization of Two Novel Biallelic PIGV Variants in a Patient With Myoclonic Seizures and Elevated Alkaline Phosphatase: A Case Report.
Intriguing role of the Golgi apparatus in astrocyte function: Implications for disorders.

J Genet. 2025 ;pii: 18. [Epub ahead of print]104

NGLY1-CDDG: report of two cases from India and brief review of literature.

Mihika B Dave, Vrajesh P Udani, Anaita U Hegde, Tester F Ashavaid, Alpa J Dherai.

N-glycanase1 (NGLY1) deficiency, an autosomal recessive disorder identified a decade ago, is categorized as a congenital disorder of deglycosylation (CDDG). This disorder arises from bi-allelic variants in the NGLY1 gene, leading to impaired protein deglycosylation. Phenotypically, individuals with NGLY1 deficiency present with intellectual disability, movement disorders, liver dysfunction, muscular hypotonia, etc., termed as NGLY1-CDDG, its diagnosis relies primarily on next generation sequencing (NGS) and till date, it has been diagnosed in over 100 patients. However, there are no previous reports on this from India. We report the first two NGLY1 cases from India in this study. These patients presented with developmental delay, movement disorder, microcephaly, hypotonia and suspicion of congenital disorder of glycosylation (CDG) and were assessed for glycosylation defect using the high pressure liquid chromatography (HPLC) based transferrin isoform analysis and whole exome sequencing (WES). Both patients exhibited a normal transferrin isoform pattern and harboured variants in NGLY1 gene. The variants, NM_018297.4:c.571C[T; p.Gln191Ter and NM_018297.4:c.707G[A; p.Trp236Ter on exons 4 and 5, respectively, identified in our patients are bi-allelic loss of function homozygous variants that have not been previously reported. These variants are inferred as pathogenic in view of genotype-phenotype correlation, parental segregation analysis, in-silico analyses, and absence of other genetic disorders. We have also summarized literature reports on NGLY1-CDDG and compared the phenotype and variants of our patients with the reported cases. These cases contribute to the clinical, biochemical, and molecular understanding of NGLY1 deficiency among Indians, thereby elucidating the presence of NGLY1-CDDG in India.
Mol Ther Methods Clin Dev. 2025 Sep 11. 33(3): 101540

Are viral vector-mediated therapies compatible with aberrant glycosylation?

I J J Muffels, R Budhraja, S Radenkovic, R Shah, A Pandey, E Morava, T Kozicz.

  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.

Keywords:  CDGs; adeno-associated virus; congenital disorders of glycosylation; glycoproteomics; glycosylation; neurodegenerative diseases; viral vector

DOI:  https://doi.org/10.1016/j.omtm.2025.101540
bioRxiv. 2025 Jul 15. pii: 2025.07.09.663964. [Epub ahead of print]

ALG13 loss-of-function alters glycosylation, impairs neuronal maturation, and drives network hypoactivity in a cortical organoid model of CDG.

Rameen Shah, Rohit Budhraja, Silvia Radenkovic, Graeme Preston, Alexia Tyler King, Sahar Sabry, Charlotte Bleukx, Ibrahim Shammas, Lyndsay Young, Jisha Chandran, Seul Kee Byeon, Ronald Hrstka, Doughlas Y Smith, Nathan P Staff, Richard Drake, Steven A Sloan, Akhilesh Pandey, Eva Morava, Tamas Kozicz.

Background: Congenital disorders of glycosylation (CDGs) are a group of rare metabolic diseases recognized for their neurological presentations, including developmental delay and seizures. However, the link between glycosylation defects and cortical brain network pathology remains elusive.
Methods: To address this unmet need, we generated iPSC derived human cortical organoids (hCOs) for ALG13-CDG, which is the second most common CDG that is also X-linked. To comprehensively understand the impact of glycosylation defects on cortical pathology in CDG, we combined electrophysiological recordings using multi-electrode arrays (MEA) with comprehensive molecular profiling via multiomics, including scRNA-seq, proteomics, glycoproteomics, N-glycan imaging, lipidomics, and metabolomics. X-inactivation status was also evaluated in both iPSCs and organoids.
Results: ALG13-CDG hCOs revealed reduced glycosylation of proteins critical for extracellular matrix (ECM), neuronal migration, lipid metabolism, calcium ion homeostasis, and neuronal excitability. Dysregulation in related pathways was corroborated by proteomics and scRNA-seq, which also showed altered communication patterns in these pathways. Trajectory analysis revealed an inversion in neuronal development, with early inhibitory and delayed excitatory development, indicating an excitatory and inhibitory (E/I) imbalance. MEA recordings demonstrated early network hypoactivity with reduced firing rates, immature burst dynamics, and shorter axonal extensions. Despite this, transcriptomic and proteomic data revealed upregulation of excitatory receptors suggesting latent hyperexcitability. Altered lipid and sugar (GlcNAc) metabolism and skewed X-inactivation were also observed.
Conclusions: Our study provides the first evidence of glycosylation defects in an ALG13-CDG human cortical organoid (hCO) model and links these defects to disrupted neuronal developmental trajectories and dysregulation of key pathways essential for brain function. We identify mistimed neuronal maturation and an excitatory/inhibitory (E/I) imbalance as early drivers of network hypoactivity and immature burst dynamics, with downstream compensatory hyperexcitability that may contribute to seizure susceptibility. While specific to ALG13-CDG, these mechanisms likely extend to other glycosylation disorders with overlapping neurological features. This work offers new mechanistic insight into cortical dysfunction associated with impaired protein glycosylation and highlights potential targets for therapeutic intervention.

DOI: https://doi.org/10.1101/2025.07.09.663964
J Biol Chem. 2025 Aug 09. pii: S0021-9258(25)02433-0. [Epub ahead of print] 110582

The glycosyltransferase ALG3 is an AKT substrate that regulates protein N-glycosylation.

Adrija J Navarro-Traxler, Laura Ghisolfi, Evan C Lien, Alex Toker.

  The PI3K/AKT signaling pathway is frequently dysregulated in cancer and controls key cellular processes such as survival, proliferation, metabolism and growth. Protein glycosylation is essential for proper protein folding and is also often deregulated in cancer. Cancer cells depend on increased protein folding to sustain oncogene-driven proliferation rates. The N-glycosyltransferase asparagine-linked glycosylation 3 homolog (ALG3), a rate-limiting enzyme during glycan biosynthesis, catalyzes the addition of the first mannose to glycans in an alpha-1,3 linkage. Here we show that ALG3 is phosphorylated downstream of the PI3K/AKT pathway in both growth factor-stimulated cells and PI3K/AKT-hyperactive cancer cells. AKT directly phosphorylates ALG3 in the amino terminal region at Ser11/Ser13. CRISPR/Cas9-mediated depletion of ALG3 leads to improper glycan formation and induction of endoplasmic reticulum stress, the unfolded protein response, and impaired cell proliferation. Phosphorylation of ALG3 at Ser11/Ser13 is required for glycosylation of cell surface receptors EGFR, HER3 and E-cadherin. These findings provide a direct link between PI3K/AKT signaling and protein glycosylation in cancer cells.

Keywords:  AKT; ALG3; N-glycosylation; PI3-kinase; glycans; phosphorylation; signaling

DOI:  https://doi.org/10.1016/j.jbc.2025.110582
Pathology. 2025 Jul 10. pii: S0031-3025(25)00222-3. [Epub ahead of print]

Laboratory diagnosis of congenital and acquired coagulopathies, including challenging-to-diagnose rare bleeding disorders.

Rabab Al Dawood, Catherine P M Hayward.

  Coagulation factors, anticoagulant proteins, and fibrinolytic proteins are important for haemostasis and may be altered by inherited and acquired conditions. Common causes of coagulopathies include vitamin K (VK) deficiency (VKD), liver disease, lupus anticoagulants, consumption or disseminated intravascular coagulation, and much less commonly, an inherited or an acquired autoimmune coagulopathy. VKD typically accounts for ≥30% of all coagulopathy referrals, and VKD is particularly common among infants but can occur at any age and in combination with other coagulopathies. Tests for fibrinogen help assess both congenital and acquired coagulopathies, with low levels predictive of poor outcomes from diverse conditions including trauma and postpartum haemorrhage. Inherited factor deficiencies are rarer, and some affect multiple coagulation factors (F), such as combined FV and FVIII deficiency, familial deficiencies of VK-dependent clotting factors, and congenital disorders of glycosylation. Additionally, there are some rare but important disorders that uniquely impair the procoagulant/anticoagulant balance, including F5 mutations that markedly increase tissue factor pathway inhibitor in plasma, causing prolonged prothrombin and activated partial thromboplastin times, without factor deficiencies. THBD mutations that increase functional, soluble thrombomodulin in plasma can also cause bleeding. Other THBD mutations cause thrombomodulin deficiency and a consumptive coagulopathy. Bleeding disorders that result from pathogenic changes to fibrinolysis include autosomal recessive, loss-of-function mutations in SERPINE1 and SERPINF2 and an autosomal dominant gain-of-function mutation affecting PLAU, in the case of Quebec platelet disorder, which causes platelet-dependent increased fibrinolysis. Laboratories need to consider strategies for diagnosing these different conditions.

Keywords:  blood coagulation disorders; blood coagulation tests; coagulation protein disorders; disseminated intravascular coagulation; fibrinolysis; lupus coagulation inhibitor; rare diseases; vitamin K deficiency bleeding

DOI:  https://doi.org/10.1016/j.pathol.2025.06.004
Am J Med Genet A. 2025 Aug 13. e64220

Functional Characterization of Two Novel Biallelic PIGV Variants in a Patient With Myoclonic Seizures and Elevated Alkaline Phosphatase: A Case Report.

Matheus Vernet Machado Bressan Wilke, Deepak Panwar, Johannes M Verheijen, Saori Umeshita, Sarah Allen Thurman, Katherine Nickels, Kahlen Darr, Yoshiko Murakami, Eric Klee, Lisa A Schimmenti, Filippo Pinto E Vairo.

  Post-translational modifications, such as glycosylation and phosphorylation, play a critical role in protein trafficking, interactions, and stability. Disruptions in these pathways can lead to glycosylphosphatidylinositol (GPI) deficiencies, which present with a spectrum of clinical features, including congenital anomalies, dysmorphic features, developmental delay, hypotonia, and epilepsy. Biallelic variants in PIGV, a key mannosyltransferase in GPI biosynthesis, cause Hyperphosphatasia with Impaired Intellectual Development Syndrome 1 (HPMRS1), a rare disorder characterized by hyperphosphatasia, seizures, developmental delay, hypotonia, abnormal MRI findings, and distinct facial dysmorphisms. Fewer than 30 cases have been reported to date. We conducted a case study and literature review; with clinical data obtained from medical records. A 2-year-old female presented with developmental delay, myoclonic epilepsy, hypotonia, and mild facial dysmorphism. Laboratory results showed elevated alkaline phosphatase (899 U/L) and low pyridoxal 5'-phosphate levels in cerebrospinal fluid (CSF). Brain MRI revealed diffuse cerebral volume loss and ventriculomegaly. Trio genome sequencing identified two PIGV variants: c.1415T>C-p.(Leu472Pro) and c.524T>C-p.(Leu175Pro). Functional studies using PIGV-knockout HEK293 cells transfected with wild-type or mutant PIGV constructs demonstrated reduced GPI-anchored protein (GPI-AP) expression under weaker promoters, indicating impaired enzymatic activity. We report two novel PIGV variants associated with HPMRS1, emphasizing the value of functional assays in variant interpretation. Our findings also highlight the diagnostic relevance of alkaline phosphatase measurement in patients with refractory seizures.

Keywords:  GPI deficiency; PIGV; developmental disorders; myoclonic seizures

DOI:  https://doi.org/10.1002/ajmg.a.64220
Neural Regen Res. 2025 Aug 13.

Intriguing role of the Golgi apparatus in astrocyte function: Implications for disorders.

Martina Polenghi, Elena Restelli, Elena Taverna, Laura Tapella.

  Cell function has a tight relationship with cell architecture. Distribution of proteins to the correct compartment is one of the functions of the traffic pathway through the Golgi apparatus. The others are to ensure proper protein folding, the addition of post-translational modifications, and delivering to intracellular and extracellular destinations. Astrocytes are fundamental homeostatic cells, controlling multiple aspects of the central nervous system physiology, such as ion balance, nutrients, blood flow, neurotransmitters, and responses to insults. Astrocytes are polarized cells, and, such as neurons, extensively use the secretory pathway for secreting factors and exposing functional receptors, channels, and transporters on the plasma membrane. In this review, we will underline the importance of studying the Golgi apparatus and the secretory pathway in astrocytes, based on the possible tight connection between the Golgi apparatus and astrocytes' homeostatic function. Given the topic of this review, we will provide examples mostly about the Golgi apparatus structure, function, localization, and its involvement in astrocytes' homeostatic response, with an insight into congenital glycosylation disorders, as an example of a potential future field in the study of astrocyte homeostatic failure and Golgi apparatus alteration.

Keywords:  Golgi apparatus; astrocytes; congenital glycosylation disorders; glia; homeostatic function; local protein translation; neurodegeneration; neuroinflammation; neuronal development; secretory pathway

DOI:  https://doi.org/10.4103/NRR.NRR-D-25-00342