The Chromatin-Modifying Protein RCOR2/CoREST2 Safeguards Axon-Dendrite Growth and Microtubule Stability in Brain Neurons.

Understanding the mechanisms that underlie neuronal dynamics is crucial to promoting brain health. The chromatin-modifying protein RCOR2 (also named CoREST2) has recently gained attention for its neuroprotective roles. Although previous work has firmly established RCOR2's importance in neurogenesis and aging, its contributions to post-mitotic neurons remain understudied. This gap limits our ability to unveil its broader significance for brain health. In this study, we used the rat primary culture of embryonic hippocampal neurons, highly enriched in pyramidal glutamatergic neurons, to show that RCOR2 preserves the structural integrity of axons and dendrites. By combining state-of-the-art imaging techniques, including confocal, AiryScan2, and STED microscopy, we unveiled that RCOR2 is highly packed within neuronal nuclei, where it maintains the spatial organization of heterochromatin. The delivery of shRNA sequences targeting RCOR2, either by transient transfection or lentiviral infection, led to its partial knockdown and a pronounced shortening of axons and dendrites. This phenotype was paralleled by an abnormal accumulation of microtubule-associated proteins (MAPs), including MAP2 and Tau, revealed by qRT-PCR, immunoblotting, and confocal imaging. Strikingly, RCOR2 knockdown neurons show increased axonal MAP2, suggesting the loss of axonal identity. Moreover, z-stack imaging revealed an abnormal increase in the tyrosinated-tubulin/acetylated-tubulin ratio-a molecular marker of microtubule (MT) stability-indicating reduced MT stability. In this regard, the treatment with a nanomolar and MT-stabilizing dose of taxol (3 nM) partially rescued the neuritic growth of RCOR2 knock-down neurons, suggesting a MT-dependent mechanism. These findings unveil neuron-specific functions of RCOR2, highlighting its protective role in sustaining neuronal architecture during early development.