Germline gain-of-function NOTCH3 mutations are an underlying cause of the CADASIL syndrome - cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. CADASIL is characterized by degeneration and loss of vascular smooth muscle cells from the arterial wall, predisposing affected individuals to an early onset stroke (Storkebaum et al. 2011). NOTCH3 promotes survival of vascular smooth muscle cells at least in part by induction of CFLAR (c FLIP), an inhibitor of FASLG activated death receptor signaling. The mechanism of NOTCH3 mediated upregulation of CFLAR is unknown; it is independent of the NOTCH3 coactivator complex and involves an unelucidated crosstalk with the RAS/RAF/MAPK pathway (Wang et al. 2002).

In rat brain, NOTCH3 and NOTCH1 are expressed at sites of adult neurogenesis, such as the dentate gyrus (Irvin et al. 2001). NOTCH3, similar to NOTCH1, promotes differentiation of the rat adult hippocampus derived multipotent neuronal progenitors into astroglia (Tanigaki et al. 2001). NOTCH1, NOTCH2, NOTCH3, and their ligand DLL1 are expressed in neuroepithelial precursor cells in the neural tube of mouse embryos. Together, they signal to inhibit neuronal differentiation of neuroepithelial precursors. Expression of NOTCH3 in mouse neuroepithelial precursors is stimulated by growth factors BMP2, FGF2, Xenopus TGF beta5 - homologous to TGFB1, LIF, and NTF3 (Faux et al. 2001).

In mouse telencephalon, NOTCH3, similar to NOTCH1, promotes radial glia and neuronal progenitor phenotype. This can, at least in part be attributed to NOTCH mediated activation of RBPJ-dependent and HES5-dependent transcription (Dang et al. 2006).

In mouse spinal cord, Notch3 is involved in neuronal differentiation and maturation. Notch3 knockout mice have a decreased number of mature inhibitory interneurons in the spinal cord, which may be involved in chronic pain conditions (Rusanescu and Mao 2014).

NOTCH3 amplification was reported in breast cancer, where NOTCH3 promotes proliferation and survival of ERBB2 negative breast cancer cells (Yamaguchi et al. 2008), and it has also been reported in ovarian cancer (Park et al. 2006). NOTCH3 signaling is involved in TGF beta (TGFB1) signaling-induced eptihelial to mesenchimal transition (EMT) (Ohashi et al. 2011, Liu et al. 2014)

NOTCH3 indirectly promotes development of regulatory T cells (Tregs). NOTCH3 signaling activates pre-TCR-dependent and PKC-theta (PRKCQ)-dependent NF-kappaB (NFKB) activation, resulting in induction of FOXP3 expression (Barbarulo et al. 2011). Deregulated NOTCH3 and pre-TCR signaling contributes to development of leukemia and lymphoma (Bellavia et al. 2000, Bellavia et al. 2002).