The FOXG1/FOXO/SMAD network balances proliferation and differentiation of cortical progenitors and activates<i>Kcnh3</i>expression in mature neurons

Riccardo Vezzali, Stefan Weise, Nicole Hellbach, Venissa Machado, Stefanie Heidrich, Tanja Vogel

Oncotarget · 2016 · 62 citations · 50 references

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// Riccardo Vezzali 1,2 , Stefan Christopher Weise 1,2 , Nicole Hellbach 1 , Venissa Machado 1 , Stefanie Heidrich 1 and Tanja Vogel 1 1 Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany 2 Faculty of Biology, University of Freiburg, Freiburg, Germany Correspondence to: Tanja Vogel, email: // Keywords : TGF&beta;; neurogenesis; transcriptional control; cerebral cortex; atypical Rett syndrome; Gerotarget Received : November 19, 2015 Accepted : May 11, 2016 Published : May 21, 2016 Abstract Transforming growth factor &beta; (TGF&beta;)-mediated anti-proliferative and differentiating effects promote neuronal differentiation during embryonic central nervous system development. TGF&beta; downstream signals, composed of activated SMAD2/3, SMAD4 and a FOXO family member, promote the expression of cyclin-dependent kinase inhibitor Cdkn1a . In early CNS development, IGF1/PI3K signaling and the transcription factor FOXG1 inhibit FOXO- and TGF&beta;-mediated Cdkn1a transcription. FOXG1 prevents cell cycle exit by binding to the SMAD/FOXO-protein complex. In this study we provide further details on the FOXG1/FOXO/SMAD transcription factor network. We identified ligands of the TGF&beta;- and IGF-family, Foxo1 , Foxo3 and Kcnh3 as novel FOXG1-target genes during telencephalic development and showed that FOXG1 interferes with Foxo1 and Tgf&beta; transcription. Our data specify that FOXO1 activates Cdkn1a transcription. This process is under control of the IGF1-pathway, as Cdkn1a transcription increases when IGF1-signaling is pharmacologically inhibited. However, overexpression of CDKN1A and knockdown of Foxo1 and Foxo3 is not sufficient for neuronal differentiation, which is probably instructed by TGF&beta;-signaling. In mature neurons, FOXG1 activates transcription of the seizure-related Kcnh3 , which might be a FOXG1-target gene involved in the FOXG1 syndrome pathology.

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