Genotype-phenotype correlations and effect of mutation location in Japanese CADASIL patients

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary cerebral small vessel disease caused by NOTCH3, and characterized by recurrent cerebral ischemic events without vascular risk factors, mood disturbance, and dementia. MRI testing shows cerebral white matter hyperintensities, especially in the external capsule and temporal pole. Typical mutations are cysteine-related missense ones located in one of 34 EGF-like repeats (EGFr) in the NOTCH3 receptor. To identify genotype-phenotype correlations, 179 Japanese CADASIL probands were recruited. Of the 68 mutations identified, p.Cys388Arg, p.Cys435Phe, p.Gly481Cys, p.Cys743Tyr, and p.Cys1009Phe were novel ones. The genotype-phenotype correlation was analyzed based on the three most common mutations: p.Arg75Pro, p.Arg141Cys, and p.Arg182Cys. p.Arg141Cys showed typical CADASIL phenotypes, whereas p.Arg75Pro showed mild and atypical phenotypes, a low frequency of stroke/TIA, high frequency of hypertension, and low frequency of temporal pole lesions. p.Arg182Cys showed various initial symptoms other than stroke/TIA. Subsequently, we analyzed the effect of the mutation location on the age at onset of stroke/TIA. We found that mutations in EGFr 1-6 excluding the cysteine-sparing mutation p.Arg75Pro were significantly correlated with a younger age at onset of stroke/TIA compared with those in EGFr 7-34. This was in agreement with a recent European report, suggesting that the effect of the mutation location is a consensus finding in CADASIL worldwide.