The present invention discloses the identification of a human hypercholesterolemia causal gene, which can be used for the diagnosis, prevention and treatment of hypercholesterolemia, more particularly familial hypercholesterolemia, as well as for the screening of therapeutically active drugs. The invention more specifically disclosed that mutations in the PCSK9 gene encoding NARC-1 causes autosomal dominant hypercholesterolemia and represent novel targets for therapeutic intervention. The invention can be used in the diagnosis of predisposition to, detection, prevention and/or treatment of coronary heart disease and, cholesterol, lipid and lipoprotein metabolism disorders, including familial hypercholesterolemia, atherogenic dyslipidemia, atherosclerosis, cardiovascular diseases.