RBPJ and systemic sclerosis: Similarly, COL1A1 mRNA levels were found to be increased in blood samples of systemic sclerosis patients and skin fibroblasts from these patients transfected with NOTCH2. NOTCH2 is a receptor, whose intracellular domain migrates to the nucleus and forms a transcriptional activator complex with Recombination signal binding protein for immunoglobulin kappa J region (RBPJ, also known as RBPSUH) upon receptor activation.