Depdc5 knockout rat: A novel model of mTORopathy

Neurobiol Dis. 2016 May;89:180-9. doi: 10.1016/j.nbd.2016.02.010. Epub 2016 Feb 9.

Abstract

DEP-domain containing 5 (DEPDC5), encoding a repressor of the mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway, has recently emerged as a major gene mutated in familial focal epilepsies and focal cortical dysplasia. Here we established a global knockout rat using TALEN technology to investigate in vivo the impact of Depdc5-deficiency. Homozygous Depdc5(-/-) embryos died from embryonic day 14.5 due to a global growth delay. Constitutive mTORC1 hyperactivation was evidenced in the brains and in cultured fibroblasts of Depdc5(-/-) embryos, as reflected by enhanced phosphorylation of its downstream effectors S6K1 and rpS6. Consistently, prenatal treatment with mTORC1 inhibitor rapamycin rescued the phenotype of Depdc5(-/-) embryos. Heterozygous Depdc5(+/-) rats developed normally and exhibited no spontaneous electroclinical seizures, but had altered cortical neuron excitability and firing patterns. Depdc5(+/-) rats displayed cortical cytomegalic dysmorphic neurons and balloon-like cells strongly expressing phosphorylated rpS6, indicative of mTORC1 upregulation, and not observed after prenatal rapamycin treatment. These neuropathological abnormalities are reminiscent of the hallmark brain pathology of human focal cortical dysplasia. Altogether, Depdc5 knockout rats exhibit multiple features of rodent models of mTORopathies, and thus, stand as a relevant model to study their underlying pathogenic mechanisms.

Keywords: DEPDC5; Familial focal epilepsy; Focal cortical dysplasia; Knockout; Rapamycin; mTOR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Cerebral Cortex / abnormalities*
  • Cerebral Cortex / drug effects
  • Cerebral Cortex / physiopathology
  • Disease Models, Animal*
  • Embryonic Development / drug effects
  • Embryonic Development / genetics*
  • Fibroblasts / metabolism
  • Gene Knockout Techniques
  • Genotype
  • Mechanistic Target of Rapamycin Complex 1
  • Multiprotein Complexes / antagonists & inhibitors
  • Multiprotein Complexes / metabolism*
  • Neurons / pathology
  • Neurons / physiology
  • Phosphorylation
  • Rats
  • Rats, Inbred F344
  • Rats, Wistar
  • Repressor Proteins / genetics*
  • Repressor Proteins / metabolism
  • Repressor Proteins / physiology*
  • Signal Transduction / drug effects
  • Sirolimus / administration & dosage
  • TOR Serine-Threonine Kinases / antagonists & inhibitors
  • TOR Serine-Threonine Kinases / metabolism*

Substances

  • Multiprotein Complexes
  • Repressor Proteins
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1
  • Sirolimus