Zhenping Gong ^1,2 Wan Wang ^2,3 Ying Zhao ^2,3 Yadan Wang ^2,4 Yaru Lu ² Ruihua Sun ^2,3,5 Haohan Zhang ^2,3,5 Fengyu Wang ^2* Zhang Jiewen ^2,3*

• ¹ Xinxiang Medical University, Xinxiang, China
• ² Department of Neurology, Henan Provincial People’s Hospital, Zhengzhou, Henan Province, China
• ³ Zhengzhou University, Zhengzhou, Henan Province, China
• ⁴ Henan University, Kaifeng, Henan Province, China
• ⁵ Academy of Medical Sciences, Zhengzhou University, Zhengzhou, Henan Province, China

Background: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is one of the most common inherited cerebral small vessel diseases caused by the NOTCH3 gene mutation. This mutation leads to the accumulation of NOTCH3 extracellular domain protein (NOTCH3 ECD ) into the cerebral arterioles, causing recurrent stroke, white matter lesions, and cognitive impairment. With the development of gene sequencing technology, cysteine-sparing mutations can also cause CADASIL disease, however, the pathogenicity and pathogenic mechanisms of cysteine-sparing mutations remain controversial. Objective: To analyze the pathogenicity and pathological features of cysteine-sparing mutations in both in vitro and in vivo mouse models. Methods: A cysteine-sparing mutant of NOTCH3 ECD R75Q was constructed by lentiviral transfection in vitro, and the NOTCH3 R75Q knock-in mouse model was constructed by CRISPR/Cas-mediated genome engineering in vivo. A cycloheximide pulse-chase experiment was used to analyze the degradation of NOTCH3 extracellular domain proteins, and the deposition characteristics of NOTCH3 ECD were quantitatively analyzed by immunohistochemical staining. The characteristics of the smooth muscle cells and granular osmiophilic materials were observed using electron microscopy.We elucidated that the NOTCH3 R75Q mutation is pathogenic. NOTCH3 ECD R75Q was found to be resistant to protein degradation and more likely to cause abnormal aggregation of NOTCH3 ECD , resulting in reduced cell activity in vitro. The NOTCH3 R75Q mouse model showed pathological characteristics of CADASIL, with age-dependent NOTCH3 ECD , granular osmiophilic material , and degenerated smooth muscle cells detected in the brain.To our knowledge, this is the first study to analyze the pathogenicity of NOTCH3 R75Q cysteine-sparing mutations in both in vitro and in vivo models. We demonstrate that NOTCH3 ECD induced by NOTCH3 R75Q mutation has toxic effects on cells and reveal the deposition characteristics of NOTCH3 ECD in the brain. This provides a feasible model and lays the foundation for further studies on the pathogenesis and therapeutic strategies of NOTCH3 cysteine-sparing mutations.