Focused ultrasound‐mediated APOE4 knockdown in mouse brain

Abstract INTRODUCTION The apolipoprotein E ( APOE ) ε4 allele is widely recognized as the strongest genetic risk factor for late‐onset Alzheimer's disease. Therapeutic strategies to reduce apoE4 expression in APOE ε4 carriers hold promise to mitigate neuroinflammatory and neurodegenerative processes driving disease progression. METHODS Focused ultrasound (FUS) was employed to transiently open the blood–brain barrier (BBB) for efficient knockdown of humanized APOE ε4 in the mouse brain via gene editing. The all‐in‐one clustered regularly interspaced short palindromic repeats (CRISPR)–based adeno‐associated virus (AAV) vectors were administered intravenously at a dose of 1.5×10 12 vg per mouse to determine the gene‐editing efficacy within the hippocampus. RESULTS FUS‐enhanced delivery of AAV resulted in a 12.6% knockdown of APOE ε4 gene expression in the targeted hippocampus, accompanied by an over 20% decrease in apoE4 protein levels and significant reductions in astrocyte and microglia levels. DISCUSSION Our findings demonstrate a noninvasive, targeted approach for APOE ε4 knockdown, highlighting FUS‐mediated brain‐directed interventions as a promising therapeutic strategy for Alzheimer's disease. Highlights Focused ultrasound (FUS) enables noninvasive, transient blood–brain barrier (BBB) opening for enhanced adeno‐associated virus (AAV) delivery. FUS‐mediated gene editing achieves a 12.6% knockdown in APOE ε4 expression within the hippocampus of mouse brain. APOE ε4 knockdown significantly reduces apoE4 protein levels and astrocyte and microglia levels. No detectable gross toxicity was observed following the FUS‐mediated gene editing.