Clinical variability of the cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy phenotype in two siblings of a large family showing the same mutation

Genetic and nongenetic factors associated with CADASIL: A retrospective cohort study

OBJECTIVE

To explore the role of cardiovascular risk factors and the different NOTCH-3 mutations to explain the variability observed in the clinical presentation of CADASIL.

METHODS

This was a retrospective cohort study of 331 individuals, 90 were carriers of four mutations in the NOTCH3 gene. These four mutations are the ones identified in our region from the genetic evaluation of probands. Cox proportional hazards models were fitted to estimate the effect of genetic and cardiovascular factors on the onset of migraine, first stroke, and dementia. Competing risk regression models considered death as risk.

RESULTS

Noncarriers (healthy controls from the same families without NOTCH3 mutations) and NOTCH3 mutation carriers had similar frequencies for all cardiovascular risk factors. Diabetes (SHR 2.74, 95% CI 1.52-4.94) was associated with a younger age at onset of strokes among carriers. Additionally, a genotype-phenotype relationship was observed among C455R mutation carriers, with higher frequency of migraines (100%), younger age at onset of migraine (median age 7 years, IQR 8) and strokes (median age 30.5 years, IQR 26). Moreover, fewer carriers of the R141C mutation exhibited migraines (20%), and it was even lower than the frequency observed in the noncarrier group (44.8%).

CONCLUSIONS

This study characterizes extended family groups, allowing us a comparison in the genotype-phenotype. The results suggest a complex interplay of genetic and cardiovascular risk factors that may help explain the variability in the clinical presentation and severity of CADASIL.

A novel cysteine-sparing G73A mutation of NOTCH3 in a Chinese CADASIL family

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common monogenic disease leading to stroke and vascular dementia. CADASIL is an inherited small blood vessel disease caused by mutations in the gene encoding the neurogenic locus notch homolog protein 3 (NOTCH3). NOTCH3 is large type I membrane receptor mainly expressed in vascular smooth muscle cells and pericytes. Most identified mutations result in insert or deletion of a cysteine residue within the EGF-like repeats. To date, some cases with a cysteine-sparing mutant have been described. Genetic analysis revealed a novel mutation in NOTCH3 in a CADASIL family. Molecular analysis revealed its potential pathogenic mechanism in causing CADASIL. In this paper, we present a Chinese family with a novel cysteine-sparing mutation in exon 3 (c.218G>C, p.G73A) of the NOTCH3 gene. Family carriers of the same mutation presented with symptoms and imaging abnormalities characteristic of CADASIL. The location of glycine 73 in between C5-C6 disulfide bond of EGF-like domain 1 shows high conservation from humans to zebra fish. It has previously been suggested that the aggregate-prone property of mutant NOTCH3 contributes to a cytotoxic effect in the pathogenic mechanism underlying CADASIL. Here, we investigated the pathogenic mechanism of the new mutation in vitro using HEK293 cells transfected with either a wild-type (WT) or c.218G>C (p.G73A) NOTCH3^ECD plasmids, and we found p.G73A NOTCH3^ECD was more prone to form aggregation and resistant to degradation. Moreover, the p.G73A NOTCH3^ECD compromised cell viability by promoting apoptosis. Two known CADASIL mutants R133C and R75P showed similar results with G73A mutants. Our study here identified G73A as a new mutation in NOTCH3 to cause CADASIL and revealed that the G73A mutation and two known mutants R75P and R133C decreased NOTCH3 protein turnover and induced cell death.

De novo mutation in the NOTCH3 gene causing CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is one of the most common hereditary forms of stroke, and migraine with aura, mood disorders and dementia. CADASIL is caused by mutations of the NOTCH3 gene. This mutation is inherited as an autosomal dominant trait. Most individuals with CADASIL have a parent with the disorder. In extremely rare cases, CADASIL may occur due to a spontaneous genetic mutation that occurs for unknown reasons (de novo mutation). We report a new case of patient with de novo mutation of the NOTCH3 gene and a condition strongly suggestive of CADASIL (migraine, stroke, and white matter abnormalities), except that this patient did not have any first-degree relatives with similar symptoms.