When a single faulty copy of one gene quietly derails a fundamental biochemical pathway, the downstream consequences cascade across the entire brain — disrupting how neurons communicate, how inhibitory circuits form, and ultimately how seizures are controlled. Understanding the precise molecular machinery behind rare epileptic encephalopathies like DHDDS-CDG could accelerate treatment strategies for broader classes of glycosylation disorders affecting thousands of children globally.
Researchers generated the first mouse model carrying the heterozygous human variant c.110G>A (p.R37H) in the Dhdds gene — the same recurrent de novo mutation observed in children diagnosed with OMIM 617836, a progressive encephalopathy characterized by cognitive delay, myoclonus, ataxia, and worsening seizures. The R37H substitution renders the DHDDS subunit of the cis-prenyltransferase (cis-PTase) enzyme catalytically inactive, even in its heterozygous state. This enzymatic failure disrupts the mevalonate pathway at a critical branch point, reducing brain dolichol levels — a lipid carrier essential for N-linked glycosylation. Without adequate dolichol, glycoproteins integral to synaptic transmission are aberrantly glycosylated, a finding confirmed through multiomics profiling of CNS tissue that also revealed sweeping perturbations in both the proteome and lipidome. Phenotypically, DhddsR37H+/- mice exhibited seizures, myoclonus, and memory deficits, accompanied by reduced density and maturity of cortical inhibitory interneurons. Notably, the carbonic anhydrase inhibitor acetazolamide — FDA-approved for epilepsy and glaucoma — reduced pentylenetetrazol-induced seizure susceptibility in the model.
This work is significant beyond its rare-disease focus. Interneuron deficits are increasingly recognized across autism, schizophrenia, and common epilepsies, and the finding that a metabolic glycosylation bottleneck can selectively impair inhibitory circuit maturation adds a mechanistic dimension rarely examined in those conditions. The dolichol-glycoprotein axis is an underexplored therapeutic target; most glycosylation disorder research focuses on later enzymatic steps. One key limitation is that heterozygous mouse models do not always faithfully replicate human haploinsufficiency phenotypes in severity or timing. Still, the identification of acetazolamide as a seizure-modifying agent in this model represents an immediately translatable hypothesis given the drug's established safety profile, making this a meaningfully actionable preclinical finding.