PPP1R21 and stroke disorder: PP1 is a ubiquitous phosphatase implicated in many brain functions including learning and memory formation.22,23 PP1 is also a key regulator of Ca2+/calmodulin (CaM)-dependent protein kinase II (CaMKII) signaling, which is crucial for Ca2+-mediated neuronal plasticity in the brain.24 Thus, although speculative, rs1842681 may modulate expression of PPP1R21, which in turn could affect brain plasticity and thereby outcome post stroke, a hypothesis that requires validation through functional experiments.