Integrative Analysis of scRNA-Seq and Bulk RNA-Seq Reveals Novel Transcription Factor Regulating Endothelial Heterogeneity Induced by Lrg1 Following Cerebral Ischemia-Reperfusion

Objective: Leucine-rich alpha-2 glycoprotein 1 (Lrg1) could regulate diverse cells in cerebral ischemia-reperfusion. Our study seeks to uncover Lrg1’s impact on endothelial cell heterogeneity via differentiation pathways and transcription factors. Method: The CSOmap model measured cell-to-brain-center distances using single-cell RNA sequencing (scRNA-seq) data in middle cerebral artery occlusion reperfusion (MCAO/R). Monocle2 mapped endothelial differentiation paths. Gene set enrichment analysis (GSEA) analyzed endothelial subcluster variations. Database searches revealed a zinc finger MIZ-type containing 1 protein-frizzled 3 (Zmiz1-Fzd3) promoter interaction. Endothelial cells were transfected with a Fzd3 promoter-luciferase plasmid. Polymerase chain reaction (PCR) and western blotting assessed MCAO/R or Zmiz1 overexpression effects on Fzd3-related mRNA and proteins. A retroviral vector carrying Zmiz1 was injected into the brains of mice to study its effect on Fzd3. Result: Lrg1−/− mice exhibited elevated cell adhesion proteins and decreased microvascular leakage after MCAO/R. CSOmap showed widened astrocyte spacing in these mice. RSS revealed Zmiz1 overexpression in MCAO/R+Lrg1−/− mice. MCAO/R and pcDNA3-Zmiz1 transfection both enhanced luciferase activity with Fzd3, indicating Zmiz1 binding to Fzd3. Retroviral Zmiz1 injection or knockdown disrupted ischemic brain tight junctions, highlighting Zmiz1’s key role in blood-brain barrier protection, likely through Fzd3 pathway modulation. Conclusion: The findings indicate Lrg1 knockout induces endothelial differentiation by activating Zmiz1, which is crucial for maintaining blood-brain barrier function, possibly via modulating the Fzd3 pathway.