ISDN2012_0258: Neural map and circuit formation in the mouse olfactory system during development

R. Sánchez 1, M. Karow 1, C. Schichor 2, G. Masserdotti 1,3, F. Ortega 1, C. Heinrich 1, S. Gascón 1,3, M.A. Khan 4, D.C. Lie 4, A. Dellavalle 5, G. Cossu 5, R. Goldbrunner 2,6, M. Götz 1,3, B. Berninger 1,3 1 Department of Physiological Genomics, Institute of Physiology, Ludwig-Maximilians University Munich, Schillerstrasse 46, D-80336 Munich, Germany 2 Tumor Biology Lab, Neurosurgical Clinic, Klinikum der Universität München, Großhadern, Marchioninistrasse 15, D-81377 Munich, Germany 3 Institute for Stem Cell Research, National Research Center for Environment and Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany 4 Research Group/Adult Neural Stem Cells and Neurogenesis, Institute of Developmental Genetics, National Research Center for Environment and Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany 5 Division of Regenerative Medicine, San Raffaele Scientific Institute, 58 via Olgettina, Milan 20132, Italy 6 Center for Neurosurgery, University Hospital of Cologne, Kerpener Strasse 62, D-50937 Cologne, Germany Reprogramming of somatic cells into neurons provides a new approach towards cell-based therapy of neurodegenerative diseases. Previous studies have shown that postnatal astroglia from the cerebral cortex of mice can be directly converted into functional neurons in vitro by forced expression of a single neurogenic transcription factor and the synergistic action of 3–4 transcription factors can induce neurogenesis from rodent and human fibroblasts. However, a major challenge for the translation of neuronal reprogramming into therapy concerns the question whether direct conversion of somatic cells into neurons can be achieved from cells residing within the adult human brain. Here we show that cells from the adult human cerebral cortex expressing pericyte hallmarks, such as the PDGF receptor(PDGF ), can be reprogrammed into III-tubulin-, MAP2and NeuN-positive neurons by co-expression of the transcription factors Mash1 (mammalian homologue of achaete-schute-1) and the SRY-related HMG box protein Sox2, but not by either factor alone. These neurons are functional as they acquire the ability of repetitive action potential firing and serve as synaptic targets for other neurons indicating their capability of integrating into neuronal networks. The pericytic origin of these neurons was further corroborated by isolating PDGFR -positive cells from human brain cultures using fluorescence-activated cell sorting and continuous live imaging during reprogramming. Genetic fate-mapping in mice expressing an inducible Cre recombinase under the tissue non-specific alkaline phosphatase promoter confirmed that pericytes from the adult cerebral cortex can be expanded and reprogrammed in vitro into neurons by Sox2 and Mash1. Our results demonstrate that direct neuronal reprogramming can be achieved from somatic cells of adult brain tissue, including of human origin. This data provide strong support for the idea that direct reprogramming of somatic cells endogenous to the adult brain represents a viable approach for cell-based therapies of neurodegenerative diseases.