Network Hypoactivity in ALG13-CDG: Disrupted Developmental Pathways and E/I Imbalance as Early Drivers of Neurological Features in CDG.

Rameen Shah, Rohit Budhhraja, 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

Journal: Cells 2026;15(2):

PMID: 41597222

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Abstract

BACKGROUND

ALG13-CDG is an X-linked N-linked glycosylation disorder caused by pathogenic variants in the glycosyltransferase ALG13, leading to severe neurological manifestations. Despite the clear CNS involvement, the impact of ALG13 dysfunction on human brain glycosylation and neurodevelopment remains unknown. We hypothesize that ALG13-CDG causes brain-specific hypoglycosylation that disrupts neurodevelopmental pathways and contributes directly to cortical network dysfunction.

METHODS

We generated iPSC-derived human cortical organoids (hCOs) from individuals with ALG13-CDG to define the impact of hypoglycosylation on cortical development and function. Electrophysiological activity was assessed using MEA recordings and integrated with multiomic profiling, including scRNA-seq, proteomics, glycoproteomics, N-glycan imaging, lipidomics, and metabolomics. X-inactivation status was evaluated in both iPSCs and hCOs.

RESULTS

ALG13-CDG hCOs showed reduced glycosylation of proteins involved in ECM organization, neuronal migration, lipid metabolism, calcium homeostasis, and neuronal excitability. These pathway disruptions were supported by proteomic and scRNA-seq data and included altered intercellular communication. Trajectory analyses revealed mistimed neuronal maturation with early inhibitory and delayed excitatory development, indicating an E/I imbalance. MEA recordings demonstrated early network hypoactivity with reduced firing rates, immature burst structure, and shortened axonal projections, while transcriptomic and proteomic signatures suggested emerging hyperexcitability. Altered lipid and GlcNAc metabolism, along with skewed X-inactivation, were also observed.

CONCLUSIONS

Our study reveals that ALG13-CDG is a disorder of brain-specific hypoglycosylation that disrupts key neurodevelopmental pathways and destabilizes cortical network function. Through integrated multiomic and functional analyses, we identify early network hypoactivity, mistimed neuronal maturation, and evolving E/I imbalance that progresses to compensatory hyperexcitability, providing a mechanistic basis for seizure vulnerability. These findings redefine ALG13-CDG as disorders of cortical network instability, offering a new framework for targeted therapeutic intervention.

Address: Department of Clinical Genomics, Mayo Clinic, Rochester, MN 55905, USA.; Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA.; Department of Genetics and Genomic Science, Icahn School of Medicine at Mount Sinai, New York, NY 10028, USA.; Renaissiance School of Medicine, Stony Brook University, Stony Brook, NY 11794, USA.; Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA.; Department of Clinical Genomics, Mayo Clinic, Rochester, MN 55905, USA.; Department of Genetics, Section Metabolic Diagnostics, University Medical Center Utrecht, 3584 EA Utrecht, The Netherlands.; Department of Clinical Genomics, Mayo Clinic, Rochester, MN 55905, USA.; Department of Genetics and Genomic Science, Icahn School of Medicine at Mount Sinai, New York, NY 10028, USA.; Department of Human Genetics, Emory University, Atlanta, GA 30322, USA.; Department of Genetics and Genomic Science, Icahn School of Medicine at Mount Sinai, New York, NY 10028, USA.; Biochemical Genetics Department, Human Genetics and Genome Research Institute, National Research Centre (NRC), Cairo 12622, Egypt.; Department of Clinical Genomics, Mayo Clinic, Rochester, MN 55905, USA.; Department of Cell and Molecular Pharmacology and Experimental Therapeutics, College of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA.; Hollings Cancer Center, Medical University of South Carolina, Charleston, SC 29425, USA.; Department of Clinical Genomics, Mayo Clinic, Rochester, MN 55905, USA.; Manipal Academy of Higher Education, Manipal 576104, Karnataka, India.; Institute of Bioinformatics, Bangalore 560066, Karnataka, India.; Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA.; Center for Regenerative Medicine, Mayo Clinic, Rochester, MN 55905, USA.; Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA.; Manipal Academy of Higher Education, Manipal 576104, Karnataka, India.; Department of Clinical Genomics, Mayo Clinic, Rochester, MN 55905, USA.; Department of Genetics and Genomic Science, Icahn School of Medicine at Mount Sinai, New York, NY 10028, USA.; Department of Biophysics, University of Pécs Medical School, 7624 Pécs, Hungary.; Department of Clinical Genomics, Mayo Clinic, Rochester, MN 55905, USA.; Department of Genetics and Genomic Science, Icahn School of Medicine at Mount Sinai, New York, NY 10028, USA.; Department of Anatomy, University of Pécs Medical School, 7624 Pécs, Hungary.

DOI: 10.3390/cells15020147

MeSH Terms: Humans, Congenital Disorders of Glycosylation, Induced Pluripotent Stem Cells, Glycosylation, Organoids, Neurons, Male