Elsevier

Neurobiology of Disease

Volume 89, May 2016, Pages 180-189
Neurobiology of Disease

Depdc5 knockout rat: A novel model of mTORopathy

https://doi.org/10.1016/j.nbd.2016.02.010Get rights and content
Under a Creative Commons license
open access

Highlights

  • Depdc5 (DEP domain containing 5) protein is critical for development.

  • Depdc5–/– rats die in utero from a global growth delay, which is rescued by prenatal rapamycin treatment.

  • Depdc5+/– rats exhibit cortical dyslamination and cytomegalic dysmorphic neurons, as in focal cortical dysplasia.

  • Depdc5-deficiency leads to mTORC1 hyperactivation in vivo.

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
mTOR
Rapamycin
Knockout

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