Archetypal Arg169Cys mutation in NOTCH3 does not drive the pathogenesis in cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy via a loss-of-function mechanism.

[cadasil]

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy , the most common heritable small vessel disease of the brain , is caused by dominant mutations in the NOTCH 3 receptor that stereotypically lead to age-dependent Notch 3 ECD deposition in the vessels . NOTCH 3 loss of function has been demonstrated for few mutations . However , whether this finding applies to all mutations and whether a loss -of-function mechanism drives the manifestations of the disease remain yet unknown . This study investigated the in vivo functionality of the Arg 169 C ys archetypal mutation .We used mice with constitutive or conditional reduction of NOTCH 3 activity , mice harboring the Arg 169 C ys mutation at the endogenous Notch 3 locus (Notch 3 Arg 170 C ys ), and mice overexpressing the Arg 169 C ys NOTCH 3 mutant (TgPAC-Notch 3 R 169 C ) on either a Notch 3 wild-type or a null background . NOTCH 3 activity was monitored in the brain arteries by measuring the expression of NOTCH 3 target genes using real-time polymerase chain reaction . Notch 3 ECD deposits were assessed by immunohistochemistry . Brain parenchyma was analyzed for vacuolation and myelin debris in the white matter and infarcts .We identified a subset of genes appropriate to detect NOTCH 3 haploinsufficiency in the adult . Expression of these genes was unaltered in Notch 3 Arg 170 C ys mice , despite marked Notch 3 ECD deposits . Elimination of wild-type NOTCH 3 did not influence the onset and burden of white matter lesions in 20 -month -old TgPAC-Notch 3 R 169 C mice , and 20 -month -old Notch 3 -null mice exhibited neither infarct nor white matter changes .These data provide strong evidence that cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy can develop without impairment of NOTCH 3 signaling and argue against a loss of NOTCH 3 function as a general driving mechanism for white matter lesions in cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy .