In vivo Imaging Genesis and Circuit Integration of Interneurons Engineered from Glia

Direct lineage reprogramming of cell identity in the nervous system offers the prospect of remodelling diseased brain circuits. Recent years have provided evidence for the possibility of converting brain glia into neurons in vivo. Yet, the process by which glial cells give up their original identity and adopt a neuronal fate remains by large enigmatic. Moreover, it is unclear how neurons induced from glia may integrate into the pre-existing circuits of non-neurogenic brain regions such as the cerebral cortex. Finally, can they participate in cortical information processing and even restore dysfunctional cortical circuits? We have discovered a specific cocktail of reprogramming factors that gives rise to induced neurons with hallmark features of fast-spiking, parvalbumin-expressing interneurons, a neuronal subtype that is highly vulnerable in neuropsychiatric and neurological disorders. Here, we aim at visualising the conversion of glia into these induced interneurons in real time by in vivo imaging. This will not only unambiguously demonstrate the genuineness of the identity switch, but also unveil cellular intermediates along the reprogramming process. By measuring single cell gene expression during conversion, we will be able to relate intermediate states to their molecular underpinnings. Moreover, in vivo imaging will allow us to follow structural remodelling of dendrites as induced interneurons integrate into pre-existing cortical circuitry. By using in vivo calcium imaging in primary visual cortex, we will examine whether induced interneurons become recruited into sensory information processing circuits. Finally, we will scrutinise induced interneurons for their ability to rescue excitation-to-inhibition balance in a mouse model of endogenous interneuron dysfunction. IMAGINE will thus break new ground towards unveiling the full potential of engineered neurogenesis for brain repair.