Enhancing induced neurogenesis in the damaged mouse cerebral cortex by activation of local microcircuits

• Applicant: Professor Dr. Benedikt Berninger
• Subject Area: Developmental Neurobiology ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 357058359

• Final Report Year: 2024

Final Report Abstract

Direct lineage reprogramming of glia into induced neurons emerges as an experimental strategy to regenerate neurons for cell-based repair of diseased brain circuits. Key challenges in the field are the conversion of glia into subtype specific neurons with properties akin to endogenous neurons as well as their functional maturation to allow for restoration of lost function. The present project aimed at elaborating on strategies for improved network integration of induced neurons in the mouse cerebral cortex, a canonically non-neurogenic region of the mammalian central nervous system. Specific aims concerned the (i) development of input and output connections of induced neurons, (ii) the effects of altered electrical activity of induced neurons on their maturation and network integration, (iii) the effects of altered microcircuit activity on the integration of induced neurons, and (iv) the effect of activity on gene expression programmes in induced neurons. During the funding period and its immediate follow-up period, we found that induced neurons not only receive functional synaptic input but also generate functional output indicating that they could indeed replace degenerated neurons. This was particularly salient in a mouse model of mesial temporal lobe epilepsy with hippocampal sclerosis where we could show that induced inhibitory neurons can functionally inhibit dentate granule neurons within the chronic epileptic brain, thereby taking on the role of endogenous interneurons that had degenerated. While raising activity in induced neurons had only minor effects on their survival and functional maturation, we found that posttranslational regulation of the proneural factors used for reprogramming could be a key mechanism for subtype specification and maturation of induced neurons: Replacing wildtype achaete scute complex like-1 (Ascl1) in the reprogramming factor cocktail by a mutant Ascl1 in which six serine residues had been mutated to alanine, thereby rending the protein phospho-site deficient (Ascl1SA6), not only led to a drastic increase in neurogenic activity, but also promoted the acquisition of hallmarks of a subclass of GABAergic interneurons such as parvalbumin expression and high-frequency firing (> 100 Hz). Finally, using an in vitro model for glia-to-neuron conversion, we could show that induced neurons do change their gene expression programmes in response to alterations of network activity that lead in endogenous neurons to homeostatic adaptations in gene expression. Overall, our work has led to important insights into the function-restoring capacities of induced neurons, their potential to acquire subtype specific neuronal features and their response to alterations in network activity.

Publications

• Direct pericyte-to-neuron reprogramming via unfolding of a neural stem cell-like program. Nature Neuroscience, 21(7), 932-940.
  Karow, Marisa; Camp, J. Gray; Falk, Sven; Gerber, Tobias; Pataskar, Abhijeet; Gac-Santel, Malgorzata; Kageyama, Jorge; Brazovskaja, Agnieska; Garding, Angela; Fan, Wenqiang; Riedemann, Therese; Casamassa, Antonella; Smiyakin, Andrej; Schichor, Christian; Götz, Magdalena; Tiwari, Vijay K.; Treutlein, Barbara & Berninger, Benedikt
  
• Reprogramming reactive glia into interneurons reduces chronic seizure activity in a mouse model of mesial temporal lobe epilepsy. Cell Stem Cell, 28(12), 2104-2121.e10.
  Lentini, Célia; d.’Orange, Marie; Marichal, Nicolás; Trottmann, Marie-Madeleine; Vignoles, Rory; Foucault, Louis; Verrier, Charlotte; Massera, Céline; Raineteau, Olivier; Conzelmann, Karl-Klaus; Rival-Gervier, Sylvie; Depaulis, Antoine; Berninger, Benedikt & Heinrich, Christophe
  
• Corrigendum: Enhanced proliferation of oligodendrocyte progenitor cells following retrovirus mediated Achaete-scute complex-like 1 overexpression in the postnatal cerebral cortex in vivo. Frontiers in Neuroscience, 17.
  Galante, Chiara; Marichal, Nicolás; Scarante, Franciele Franco; Ghayad, Litsa Maria; Shi, Youran; Schuurmans, Carol; Berninger, Benedikt & Péron, Sophie
  
• Lmo4 synergizes with Fezf2 to promote direct in vivo reprogramming of upper layer cortical neurons and cortical glia towards deep-layer neuron identities. PLOS Biology, 21(8), e3002237.
  Felske, Torsten; Tocco, Chiara; Péron, Sophie; Harb, Kawssar; Alfano, Christian; Galante, Chiara; Berninger, Benedikt & Studer, Michèle
  
• Programming of neural progenitors of the adult subependymal zone towards a glutamatergic neuron lineage by neurogenin 2. Stem Cell Reports, 18(12), 2418-2433.
  Péron, Sophie; Miyakoshi, Leo M.; Brill, Monika S.; Manzano-Franco, Diana; Serrano-López, Julia; Fan, Wenqiang; Marichal, Nicolás; Ghanem, Alexander; Conzelmann, Karl-Klaus; Karow, Marisa; Ortega, Felipe; Gascón, Sergio & Berninger, Benedikt
  
• Reprogramming early cortical astroglia into neurons with hallmarks of fast-spiking parvalbumin-positive interneurons by phospho-site deficient Ascl1. Cold Spring Harbor Laboratory.
  Marichal, Nicolás; Péron, Sophie; Beltran, Arranz Ana; Galante, Chiara; Scarante, Franciele Franco; Wiffen, Rebecca; Schuurmans, Carol; Karow, Marisa; Gascón, Sergio & Berninger, Benedikt