Leducq Center Against Small Vessel Disease

CADASIL/CARASIL: GOM proteome, altered expression of Notch3 targets, and vascular functional deficits

Notch3^ECD-containing aggregates are likely the earliest manifestation of the disease in both patients and mouse models. Our working hypothesis is that excess Notch3^ECD sequesters functionally important SM matricellular proteins in GOM. In support of this, we have recently found that Timp3 (tissue inhibitor of metalloproteinase 3) and vitronectin are major components of Notch3^ECD-containing aggregates and GOM (Joutel). This first year plan focuses on the comprehensive identification of GOM constituents using an established proteomic approach on brain vessel samples from post-mortem CADASIL patients (Joutel).

CADASIL (TgPAC-Notch3^R169C) mice exhibit impaired autoregulation of CBF, diminished pressure-induced constrictions (myogenic tone) of isolated pial arteries/parenchymal arterioles, and compromised NVC²¹ (Nelson, Joutel). In addition, CADASIL (TgSM22-HumNotch3^R90C) mice show increased susceptibility to CSD, and are more sensitive to cardiovascular challenges, such as stroke-associated cerebral ischemia and cerebral hypoperfusion⁸ (Ayata, Joutel). The molecular basis for the attenuation of myogenic tone in parenchymal and pial arterioles will be determined (Nelson). We have recently found that SMCs in pressurized parenchymal arterioles from CADASIL mice are significantly more hyperpolarized than those from wild-type (WT) mice and that the current density of SMC voltage-dependent K⁺ (K_V) channels is elevated (Nelson, Joutel), suggesting that K⁺ channel upregulation may be involved in autoregulation dysfunction. The recent finding that K_V1.5 is a Notch3^ICD target (Joutel) raises the interesting possibility that, in addition to GOM formation, altered regulation of Notch3^ICD targets may contribute to functional vascular deficits in CADASIL. Loss of myogenic reactivity in parenchymal arterioles may impact regulation of microvascular pressure as well as autoregulation of CBF. To examine the hemodynamic impact of these changes, we (Faraci) also have the unique capability to measure microvascular pressure (local perfusion pressure) as well as vasomotor responses. The effect of CADASIL mutations (R90C, R169C) on the susceptibility to CSD as well as its basis (vascular vs. neuronal) will also be determined (Ayata).

Another intriguing possibility, which will be explored, is that the numerous CSDs that occur in susceptible CADASIL patients during their young adult life may have adverse consequences on the tissue as well as the vasculature. CARASIL (HtrA1^-/-) mice will undergo in-depth histological and biochemical analyses to establish their suitability as a disease model for CARASIL and cerebral SVD (Dichgans).