PCSK9 and Hypercholesterolemia: Mutations of the genes that encode the proteins involved in LDL uptake and catabolism (i.e. LDL-receptor by LDLR gene, apolipoprotein-B (ApoB) by APOB gene, LDL receptor adaptor protein by LDLRAP1 gene and PCSK9 protein by PCSK9 gene) are well-known to cause familial hypercholesterolemia by defective LDL uptake and degradation, which in-turn leads to an elevation of plasma LDL-C level, producing the hypercholesterolemia phenotype.