Novel Cysteine-Sparing Hypomorphic NOTCH3 A1604T Mutation Observed in a Family With Migraine and White Matter Lesions

Objective

To conduct a clinical study of a family with neurologic symptoms and findings carrying a novel NOTCH3 mutation and to analyze the molecular consequences of the mutation.

Methods

We analyzed a family with complex neurologic symptoms by MRI and neurologic examinations. Exome sequencing of the NOTCH3 locus was conducted, and whole-genome sequencing was performed to identify COL4A1, COL4A2, and HTRA1 mutations. Cell lines expressing the normal or NOTCH3A1604T receptors were analyzed to assess proteolytic processing, cell morphology, receptor routing, and receptor signaling.

Results

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common hereditary form of cerebral small vessel disease (SVD) and caused by mutations in the NOTCH3 gene. Most CADASIL mutations alter the number of cysteine residues in the extracellular domain of the NOTCH3 receptor, but in this article, we describe a family in which some members carry a novel cysteine-sparing NOTCH3 mutation (c.4810 G>A, p.Ala1604Thr). Two of 3 siblings heterozygous for the NOTCH3A1604T mutation presented with migraine and white matter lesions (WMLs), the latter of a type related to but distinct from what is normally observed in CADASIL. Two other members instead carried a novel COL4A1 missense mutation (c.4795 G>A; p.(Ala1599Thr)). The NOTCH3A1604T receptor was aberrantly processed, showed reduced presence at the cell surface, and less efficiently activated Notch downstream target genes.

Conclusions

We identify a family with migraine and WML in which some members carry a cysteine-sparing hypomorphic NOTCH3 mutation. Although a causal relationship is not established, we believe that the observations contribute to the discussion on dysregulated Notch signaling in cerebral SVDs.

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