Gain-of-function PPM1D mutations attenuate ischemic stroke
Identification of genetic aberrations in stroke, the second leading cause of death worldwide, is of paramount importance for understanding the disease pathogenesis and generating new therapies. Whole-genome sequencing from 10,241 ischemic stroke patients identified eight patients carrying gain-of-function mutations on coding variants in protein phosphatase magnesium-dependent 1 d (PPM1D) gene. Patients carrying PPM1D mutations exhibit better stroke-related clinical phenotypes, including improvements in systolic blood pressure, fibrinogen level, low-density lipoprotein, and plateletcrit level. Experimental brain ischemia in Ppm1d-deficient (Ppm1d-/-) mice resulted in enlarged lesions and pronounced neurological impairments. Spatial transcriptomics revealed a distinct Ppm1d-associated gene expression pattern, indicating disrupted endothelial homeostasis during ischemic brain injury. Proteomic analysis demonstrated that differentially expressed proteins in primary brain endothelial cells from Ppm1d-/- mice were significantly enriched in the peroxisome proliferator-activated receptors (PPARs)-mediated metabolic signaling. Mechanistically, Ppm1d deficiency promoted aberrant fatty acid ß-oxidation and increased oxidative stress, which impair endothelial cell function through the PPARa pathway. A small molecule, T2755, was identified to engage Trp427 and stabilize PPM1D protein, thereby mitigating ischemic brain injury in mice. Collectively, we found that PPM1D protects against ischemic brain injury and validates its pharmacological stabilizer T2755 as a promising therapy for ischemic stroke. Overall design: To explore the impact of Ppm1d on key pathological events post-brain ischemia, spatial transcriptomics was performed on the ischemic hemisphere of Ppm1d+/+and Ppm1d-/- mice following stroke. A 30 minutes middle cerebral artery occlusion (MCAO) model was utilized to induce a controlled infarct lesion, facilitating spatial transcriptomic analysis and ensuring a comprehensive evaluation of the anatomical structures in the peri-lesion region.