PIGA mutations cause early-onset epileptic encephalopathies and distinctive features

Area of Science:

• Genetics
• Neuroscience
• Biochemistry

Background:

• Early-onset epileptic encephalopathies (EOEEs) are severe neurological disorders.
• Mutations in the PIGA gene are implicated in glycosylphosphatidylinositol (GPI) anchor biosynthesis.
• The role of PIGA mutations in the clinical spectrum of EOEEs requires further investigation.

Purpose of the Study:

• To investigate the clinical spectrum of early-onset epileptic encephalopathies (EOEEs) caused by mutations in the PIGA gene.
• To analyze the impact of PIGA mutations on glycosylphosphatidylinositol (GPI) anchor biosynthesis.
• To correlate PIGA mutation severity with clinical phenotypes in EOEE patients.

Main Methods:

• Whole-exome sequencing was performed on 172 patients with EOEEs.
• PIGA mutations were identified and analyzed.
• Flow cytometry was used to assess GPI-anchored protein expression in patient blood granulocytes and cell lines.

Main Results:

• Four PIGA mutations were identified in patients with early myoclonic encephalopathy, West syndrome, or unclassified EOEE.
• Reduced expression of GPI-anchored proteins was observed in patients' blood granulocytes.
• PIGA mutations resulted in variable loss of PIGA activity, correlating with distinct clinical phenotypes: severe (myoclonus, dysmorphic face) and less severe (intellectual disability, treatable seizures).

Conclusions:

• PIGA mutations are a confirmed genetic cause of EOEE.
• Deficiencies in GPI-anchor biosynthesis due to PIGA mutations are suggested as an underlying mechanism for EOEE.
• The study highlights the phenotypic variability associated with PIGA mutations in EOEE.