The phenotypic landscape of a Tbc1d24 mutant mouse includes convulsive seizures resembling human early infantile epileptic encephalopathy

Hum Mol Genet. 2019 May 1;28(9):1530-1547. doi: 10.1093/hmg/ddy445.


Epilepsy, deafness, onychodystrophy, osteodystrophy and intellectual disability are associated with a spectrum of mutations of human TBC1D24. The mechanisms underlying TBC1D24-associated disorders and the functions of TBC1D24 are not well understood. Using CRISPR-Cas9 genome editing, we engineered a mouse with a premature translation stop codon equivalent to human S324Tfs*3, a recessive mutation of TBC1D24 associated with early infantile epileptic encephalopathy (EIEE). Homozygous S324Tfs*3 mice have normal auditory and vestibular functions but show an abrupt onset of spontaneous seizures at postnatal day 15 recapitulating human EIEE. The S324Tfs*3 variant is located in an alternatively spliced micro-exon encoding six perfectly conserved amino acids incorporated postnatally into TBC1D24 protein due to a micro-exon utilization switch. During embryonic and early postnatal development, S324Tfs*3 homozygotes produce predominantly the shorter wild-type TBC1D24 protein isoform that omits the micro-exon. S324Tfs*3 homozygotes show an abrupt onset of seizures at P15 that correlates with a developmental switch to utilization of the micro-exon. A mouse deficient for alternative splice factor SRRM3 impairs incorporation of the Tbc1d24 micro-exon. Wild-type Tbc1d24 mRNA is abundantly expressed in the hippocampus using RNAscope in situ hybridization. Immunogold electron microscopy using a TBC1D24-specific antibody revealed that TBC1D24 is associated with clathrin-coated vesicles and synapses of hippocampal neurons, suggesting a crucial role of TBC1D24 in vesicle trafficking important for neuronal signal transmission. This is the first characterization of a mouse model of human TBC1D24-associated EIEE that can now be used to screen for antiepileptogenic drugs ameliorating TBCID24 seizure disorders.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Alleles
  • Animals
  • Biomarkers
  • Brain / metabolism
  • DNA Mutational Analysis
  • GTPase-Activating Proteins / genetics*
  • GTPase-Activating Proteins / metabolism
  • Gene Expression
  • Genetic Association Studies*
  • Genetic Loci
  • Genetic Predisposition to Disease*
  • Humans
  • Male
  • Mice
  • Mutation*
  • Neurons / metabolism
  • Phenotype*
  • Protein Binding
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Spasms, Infantile / diagnosis*
  • Spasms, Infantile / genetics*


  • Biomarkers
  • GTPase-Activating Proteins
  • RNA, Messenger
  • TBC1D24 protein, human

Supplementary concepts

  • Infantile Epileptic-Dyskinetic Encephalopathy