CST3, also known as Cystatin-C is a member of family 2 of the cystatin superfamily. This protein is a secreted type 2 cysteine protease inhibitor synthesized in all nucleated cells, has been proposed as a replacement for serum creatinine for the assessment of renal function, particularly to detect small reductions in glomerular filtration rate. It is involved in processes such as tumor invasion and metastasis, inflammation and some neurological diseases. It inhibits many cysteine proteases such as papain and cathepsins B, H, K, L and S. It indicates that a murine model should be relevant for studies of the human disease, hereditary Cystatin C amyloid angiopathy.