Expression of constitutively active FOXO3 in murine forebrain leads to a loss of neural progenitors

We have generated transgenic mice with tetracycline-regulated conditional expression of a constitutively active allele of FoxO3 under the control of the forebrain-specific CaMKIIa promoter. In adult animals, there was a reduction of brain weight by 30% and an almost complete loss of the dorsal dentate gyrus with normal cortical layering. Interestingly, the adult mice showed motor hyperactivity and a selective loss of long-term memory with normal spatial learning. We observed enhanced apoptosis starting from day E10.5. Performing microarray expression analyses and Q-PCR validation with E12.5 forebrain RNA, we observed an over-representation of thalamic markers and an under-representation of cortical markers in transgenic as compared to control animals. Immunohistochemical data show a loss of progenitors in the lateral ventricles. Up-regulation of Pik3ip1 as a target gene of FoxO3 could be responsible for the observed increase in apoptosis. The obtained forebrain expression signature is reminiscent of a Pax6 knockdown phenotype showing that expression of this FoxO3 allele during development affected neural progenitor survival and overall brain development. Conclusion: Neural progenitors are vulnerable to constitutively active FoxO3-induced apoptosis.

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Schmidt-Strassburger U, Schips TG, Maier HJ, Kloiber K, Mannella F, Braunstein KE, Holzmann K, Ushmorov A, Liebau S, Boeckers TM, Wirth T