[MS10-4B-4] A human iPSC model of STXBP1-related epileptic encephalopathy uncovers specific neural dysfunctions
[Introduction] Mutations of STXBP1 are among the most frequent genetic causes of epileptic encephalopathies. STXBP1 encodes syntaxin-binding protein 1 (STXBP1), an essential protein for synaptic vesicle exocytosis and trafficking of syntaxin-1. However, the precise pathophysiology caused by STXBP1 haploinsufficiency has not been elucidated. Using patient-derived induced pluripotent stem cells (iPSCs), we aimed to establish a human neuronal model for STXBP1 haploinsufficiency and determine the pathogenic mechanisms of STXBP1 encephalopathy.
[Methodology] We generated iPSC lines from a patient with Ohtahara syndrome (OS) harboring a heterozygous nonsense mutation of STXBP1 (c.1099C>T; p.R367X) and his healthy father as controls. We differentiated the iPSCs into neurons and analyzed them.
[Results] Both STXBP1 mRNA and STXBP1 protein expression levels of OS-derived neurons were approximately 50% lower than that of control-derived neurons. Thus, we established a patient-derived human neuronal model of STXBP1 haploinsufficiency. Western blot and immunocytochemistry assays revealed that OS-derived neurons show reduced levels and mislocalization of syntaxin-1, a component of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. Additionally, OS-derived neurons have impaired neurite extension.
[Conclusions] This iPSC model enables us to investigate the pathogenic mechanisms of STXBP1 encephalopathy throughout the stages of neurodevelopment. Reduced expression of STXBP1 leads to changes in the expression and intracellular localization of syntaxin-1 that may contribute to the devastating phenotype of STXBP1 encephalopathy.
[Methodology] We generated iPSC lines from a patient with Ohtahara syndrome (OS) harboring a heterozygous nonsense mutation of STXBP1 (c.1099C>T; p.R367X) and his healthy father as controls. We differentiated the iPSCs into neurons and analyzed them.
[Results] Both STXBP1 mRNA and STXBP1 protein expression levels of OS-derived neurons were approximately 50% lower than that of control-derived neurons. Thus, we established a patient-derived human neuronal model of STXBP1 haploinsufficiency. Western blot and immunocytochemistry assays revealed that OS-derived neurons show reduced levels and mislocalization of syntaxin-1, a component of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. Additionally, OS-derived neurons have impaired neurite extension.
[Conclusions] This iPSC model enables us to investigate the pathogenic mechanisms of STXBP1 encephalopathy throughout the stages of neurodevelopment. Reduced expression of STXBP1 leads to changes in the expression and intracellular localization of syntaxin-1 that may contribute to the devastating phenotype of STXBP1 encephalopathy.