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Glycogen hyperphosphorylation underlies lafora body formation.

Julie Turnbull1, Peixiang Wang, Jean-Marie Girard

  • 1Department of Genetics and Genome Biology, Hospital for Sick Children, Toronto, Ontario, Canada.

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Lafora bodies in Lafora disease result from glycogen hyperphosphorylation, not increased glycogen synthase. This finding clarifies the pathogenesis of this fatal epilepsy by identifying a common molecular cause.

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Area of Science:

  • Biochemistry
  • Neuroscience
  • Molecular Biology

Background:

  • Glycogen's solubility is crucial for its function and relies on extensive branching.
  • Lafora bodies, insoluble polyglucans, accumulate in neurons in Lafora disease, causing fatal epilepsy.
  • Lafora disease stems from deficiencies in laforin phosphatase or malin ubiquitin ligase.

Purpose of the Study:

  • To investigate the molecular mechanisms underlying Lafora body formation in malin-deficient Lafora disease.
  • To differentiate between two leading hypotheses: increased glycogen synthase activity versus increased glycogen phosphate.

Main Methods:

  • Generation of malin-deficient mice to model Lafora disease.
  • Assessment of glycogen synthase and glycogen phosphate levels in malin-deficient mice.

Main Results:

  • Malin-deficient mice exhibit Lafora body pathology mirroring human Lafora disease.
  • No significant changes in glycogen synthase quantity or activity were observed.
  • A significant increase in glycogen phosphate levels was detected.

Conclusions:

  • Glycogen hyperphosphorylation is identified as the primary cause of Lafora body pathogenesis.
  • This finding unifies the understanding of Lafora body formation in both forms of the disease.