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How neurons can maintain cellular identity over an entire life span remains largely unknown. Here, we show that maintenance of identity in differentiated dopaminergic and serotonergic neurons is critically reliant on the Polycomb repressive complex 2 (PRC2). Deletion of the obligate PRC2 component, Eed, in these neurons resulted in global loss of H3K27me3, followed by a gradual activation of genes harboring both H3K27me3 and H3K9me3 modifications. Notably, H3K9me3 was lost at these PRC2 targets before gene activation. Neuronal survival was not compromised; instead, there was a reduction in subtype-specific gene expression and a progressive impairment of dopaminergic and serotonergic neuronal function, leading to behavioral deficits characteristic of Parkinson's disease and anxiety. Single-cell analysis revealed subtype-specific vulnerability to loss of PRC2 repression in dopamine neurons of the substantia nigra. Our study reveals that a PRC2-dependent nonpermissive chromatin state is essential to maintain the subtype identity and function of dopaminergic and serotonergic neurons.

One-photon calcium imaging using head-mounted miniaturized endoscopes ("miniscopes") is a powerful method for imaging neuron activity of genetically-labeled neurons with single-cellresolution from awake and freely moving animals. A major challenge in analysis of imagingdata is the recording of single neurons over multiple days. To improve speed and accuracy,we created a software package for calcium extraction with a highly optimized GPU-basedimplementation of the Constrained Non-negative Matrix Factorization (CNMF) algorithmwith OASIS deconvolution of the traces. Additionally, we introduce negentropy as a robust statistical measure to rapidly initialize spatial footprints as well as to automatically find the best regularization and time constant of the OASIS deconvolution. We found that our implementation is 50x-100x faster compared to a state-of-the-art calcium processing tool. The significant speed advantage enables processing of a large number of calcium videos from separate recording days as a single concatenated video, making it feasible to follow individual cells across multiple days in a consistent manner. We demonstrate how our approach can capture the neural dynamics across more than two weeks of daily recordings with 1-photon miniscope of Oprm1-Cre+ striatal projection neurons as mice develop a task strategy in a maze., QC 20231101