Whole-Exome sequencing identifies GYS2 biallelic variants in individuals with suspected epilepsy

Muhammad Ilyas, Dorothea Holzwarth, Rafaqat Ishaq, Yasir Ali, Umme Habiba, Asad Mehmood Raja, Sadia Saeed, Uzma Abdullah, Sadiq Noor Khan, Ata Ullah, Ghazala Kaukab Raja, Shahid Mehmood Baig, Walid Fazeli, Wolfram S. Kunz, Pakeeza Arzoo Shaiq

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Adequate glucose supply is essential for brain function, therefore hypoglycemic states may lead to seizures. Since blood glucose supply for brain is buffered by liver glycogen, an impairment of liver glycogen synthesis by mutations in the liver glycogen synthase gene (GYS2) might result in a substantial neurological involvement. Here, we describe the phenotypes of affected siblings of two families harboring biallelic mutations in GYS2. Methods: Two suspected families - a multiplex Pakistani family (family A) with three affected siblings and a family of Moroccan origin (family B) with a single affected child who presented with seizures and reduced fasting blood glucose levels were genetically characterized. Whole exome sequencing (WES) was performed on the index patients, followed by Sanger sequencing-based segregation analyses on all available members of both families. Results: The variant prioritization of WES and later Sanger sequencing confirmed three mutations in the GYS2 gene (12p12.1) consistent with an autosomal recessive pattern of inheritance. A homozygous splice acceptor site variant (NM_021957.3, c. 1646 -2A>G) segregated in family A. Two novel compound heterozygous variants (NM_021957.3: c.343G>A; p.Val115Met and NM_021957.3: c.875A>T; p.Glu292Val) were detected in family B, suggesting glycogen storage disorder. A special diet designed to avoid hypoglycemia, in addition to change of the anti-seizure medication led to reduction in seizure frequency. Conclusions: This study suggests that the seizures in patients initially diagnosed with epilepsy might be directly caused, or influenced by hypoglycemia due to pathogenic variants in the GYS2 gene.

Original languageEnglish
Pages (from-to)74-80
Number of pages7
JournalSeizure : the journal of the British Epilepsy Association
Volume116
DOIs
Publication statusPublished - Mar 2024
Externally publishedYes

Keywords

  • Biallelic GYS2 mutations
  • Coma
  • Compound heterozygous
  • Hypoglycemia
  • Seizure
  • Splice-site mutation
  • Whole-Exome sequencing

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