Small in-frame deletions and missense mutations in CADASIL: 3D models predict misfolding of Notch3 EGF-like repeat domains

CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) is a hereditary microangiopathic condition causin g stroke in young adults. The responsible gene has recently been identified as the Notch3 gene. Notch3 encodes a large transmembrane receptor with 34 extracellularly localised epidermal growth factor-like (EGF) repeat domains . We screened 71 unrelated CADASIL families for mutations in two exons codi ng for the first five EGF-like repeats and found mutations in 70% of the fa milies (n = 50). Two types of mutations were identified: 48 families (96%) had missense mutations and two families (4%) had small in-frame deletions. Seven mutations occurred multiple times. All of them are C to T transitions that affect CpG dinucleotides, suggesting that their multiple occurrence i s due to the hypermutability of this sequence. All mutations, including the two deletions, result in the gain or loss of a cysteine residue, thus subs tantiating the pivotal role of an uneven number of cysteine residues within EGF-like repeat domains of Notch3 in the pathogenesis of CADASIL. To study the potential effects of these mutations 3D homology models of the first s ix ECF domains were generated on the basis of NMR data from human fibrillin -1. These models predict domain misfolding for a subset of mutations.