In CADASIL , the long arm of chromosome 19 causes an abnormal accumulation of Notch 3 .
Mutations in the Notch 3 gene ( on the long arm of chromosome 19 ) cause an abnormal accumulation of Notch 3 at the cytoplasmic membrane of vascular smooth-muscle cells both in cerebral and extracerebral vessels , seen as granular osmiophilic deposits on electron microscopy.
CADASIL