Genetic study of the NOTCH3 gene in CADASIL patients

Abstract

Background: Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a monogenic, hereditary, neurological syndrome characterized by small vessel disease (SVD), stroke, vascular cognitive impairment and dementia. It is caused by mutations in the NOTCH3  gene, affecting the number of cysteines in the extracellular domain of the receptor, causing protein misfolding and receptor aggregation. The pathogenic role of cysteine-sparing NOTCH3 missense mutations in patients with typical clinical CADASIL syndrome is unknown. No therapies are available for this condition.

Objective: Genetic study of the NOTCH3 gene in CADASIL patients who were referred to the Fazeli-Sanati Genetics Laboratory.

Subjects and methods: Peripheral blood samples were collected from 10 CADASIL patients to extract genomic DNA. DNA sequences of exons 2–8, 11–12 and 18–19, where NOTCH3 mutations are typically located; were amplified by using PCR and analyzed by direct sequencing.

Results: 11 NOTCH3 exons were analyzed. Homozygous IVS7 + 15A>G mutation were found in five patients, Homozygous IVS7 + 16A>G mutation in one patient, Heterozygous for the Pro109Thr and Pro203His mutations in one patient, which were not reported previously. Heterozygous C395R and R153C mutations were found in two patients. One of the patients has no mutation in 11 analyzed NOTCH3 exons.

Conclusion: We found four novel mutations (P109T, P203H, IVS7 + 15A>G and IVS7 + 16A>G) and 2 reported NOTCH3 mutations. Exon 4 and Intron 7 are hotspots in the patients we examined with the NOTCH3 mutations. These findings broaden the mutational spectrum of CADASIL.

Keywords:  CADASIL, NOTCH3, Mutation, Exon