CB1 Cannabinoid Receptor-Dependent Activation of mTORC1/Pax6 Signaling Drives Tbr2 Expression and Basal Progenitor Expansion in the Developing Mouse Cortex

Cereb Cortex. 2015 Sep;25(9):2395-408. doi: 10.1093/cercor/bhu039. Epub 2014 Mar 7.

Abstract

The CB1 cannabinoid receptor regulates cortical progenitor proliferation during embryonic development, but the molecular mechanism of this action remains unknown. Here, we report that CB1-deficient mouse embryos show premature cell cycle exit, decreased Pax6- and Tbr2-positive cell number, and reduced mammalian target of rapamycin complex 1 (mTORC1) activation in the ventricular and subventricular cortical zones. Pharmacological stimulation of the CB1 receptor in cortical slices and progenitor cell cultures activated the mTORC1 pathway and increased the number of Pax6- and Tbr2-expressing cells. Likewise, acute CB1 knockdown in utero reduced mTORC1 activation and cannabinoid-induced Tbr2-positive cell generation. Luciferase reporter and chromatin immunoprecipitation assays revealed that the CB1 receptor drives Tbr2 expression downstream of Pax6 induction in an mTORC1-dependent manner. Altogether, our results demonstrate that the CB1 receptor tunes dorsal telencephalic progenitor proliferation by sustaining the transcriptional activity of the Pax6-Tbr2 axis via the mTORC1 pathway, and suggest that alterations of CB1 receptor signaling, by producing the missexpression of progenitor identity determinants may contribute to neurodevelopmental alterations.

Keywords: Eomes; basal progenitors; cannabinoid; corticogenesis; mTORC1.

MeSH terms

  • Animals
  • Animals, Newborn
  • Cell Culture Techniques
  • Cerebral Cortex* / cytology
  • Cerebral Cortex* / embryology
  • Cerebral Cortex* / growth & development
  • Embryo, Mammalian
  • Eye Proteins / genetics
  • Eye Proteins / metabolism
  • Gene Expression Regulation, Developmental / genetics*
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism
  • Ki-67 Antigen / metabolism
  • Mechanistic Target of Rapamycin Complex 1
  • Mice
  • Mice, Transgenic
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism
  • Mutation / genetics
  • Nerve Tissue Proteins / metabolism
  • Organ Culture Techniques
  • PAX6 Transcription Factor
  • Paired Box Transcription Factors / genetics
  • Paired Box Transcription Factors / metabolism
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • Receptor, Cannabinoid, CB1 / genetics
  • Receptor, Cannabinoid, CB1 / metabolism*
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Signal Transduction / genetics*
  • Stem Cells / physiology*
  • T-Box Domain Proteins / genetics
  • T-Box Domain Proteins / metabolism*
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism

Substances

  • Eomes protein, mouse
  • Eye Proteins
  • Homeodomain Proteins
  • Ki-67 Antigen
  • Multiprotein Complexes
  • Nerve Tissue Proteins
  • PAX6 Transcription Factor
  • Paired Box Transcription Factors
  • Pax6 protein, mouse
  • RNA, Small Interfering
  • Receptor, Cannabinoid, CB1
  • Repressor Proteins
  • T-Box Domain Proteins
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1