De novo mutations in epileptic encephalopathies

Area of Science:

• Genetics
• Neuroscience
• Pediatrics

Background:

• Epileptic encephalopathies are severe childhood epilepsy disorders with often unknown causes.
• Infantile spasms and Lennox-Gastaut syndrome are classical, devastating forms of early-onset epilepsy.

Purpose of the Study:

• To screen for de novo mutations in patients diagnosed with infantile spasms and Lennox-Gastaut syndrome.
• To identify genetic underpinnings of severe childhood epilepsy disorders.

Main Methods:

• Whole-exome sequencing of 264 probands and their parents.
• Confirmation of 329 de novo mutations.
• Likelihood analysis to identify genes intolerant to functional variation.

Main Results:

• A significant excess of de novo mutations was found in genes intolerant to functional variation (P = 2.9 × 10⁻³).
• De novo mutations in GABRB3 and ALG13 showed strong statistical association with epileptic encephalopathy (P = 4.1 × 10⁻¹⁰ and P = 7.8 × 10⁻¹², respectively).
• Other associated genes include CACNA1A, CHD2, FLNA, GABRA1, GRIN1, GRIN2B, HNRNPU, IQSEC2, MTOR, and NEDD4L.

Conclusions:

• De novo mutations in evolutionarily constrained genes are a significant cause of infantile spasms and Lennox-Gastaut syndrome.
• The identified mutations provide critical insights into the genetic etiology of severe childhood epilepsies.
• Enrichment of mutations in gene sets regulated by the fragile X protein suggests overlap with other neurodevelopmental disorders like autism spectrum disorders.