Post-stroke dendritic arbor regrowth – a cortical repair process requiring the actin nucleator Cobl

Ischemic stroke is a major cause of death and long-term disability. We demonstrate that middle cerebral artery occlusion in mice leads to a strong decline in dendritic arborization of penumbral neurons. These defects were subsequently repaired by an ipsilateral recovery process requiring the actin nucleator Cobl. Ischemic stroke and excitotoxicity, caused by calpain-mediated proteolysis, significantly reduced Cobl levels. In an apparently unique manner among excitotoxicity-affected proteins, this Cobl decline was rapidly restored by increased mRNA expression and Cobl then played a pivotal role in post-stroke dendritic arbor repair in peri-infarct areas. In Cobl KO mice, the dendritic repair window determined to span day 2-4 post-stroke in WT strikingly passed without any dendritic regrowth. Instead, Cobl KO penumbral neurons of the primary motor cortex continued to show the dendritic impairments caused by stroke. Our results thereby highlight a powerful post-stroke recovery process and identified causal molecular mechanisms critical during post-stroke repair.