Missense Mutations in the PCSK9 Gene Are Associated With Hypocholesterolemia and Possibly Increased Response to Statin Therapy

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Abstract
Objective— The proprotein convertase subtilisin/kexin type 9 (PCSK9) gene encodes a proprotein convertase that causes degradation of cell surface low-density lipoprotein receptors (LDLRs). Mutations in the PCSK9 gene that disrupt the normal function of PCSK9 could therefore result in increased number of LDLRs and hypocholesterolemia. Also, the cholesterol-lowering effect of statins could be increased in subjects carrying mutations in the PCSK9 gene. Methods and Results— We have screened 38 unrelated hypocholesterolemic subjects as well as 25 unrelated familial hypercholesterolemia (FH) heterozygotes who responded particularly well to statin therapy for mutations in the 12 exons of the PCSK9 gene by DNA sequencing. Six of the 38 (15.8%) hypocholesterolemic subjects were heterozygous for 1 of the 3 mutations R46L, G106R, or R237W in the PCSK9 gene. In the group of 25 FH heterozygotes who responded particularly well to statin therapy, 3 (8.8%) were heterozygous for mutations R46L or N157K in the PCSK9 gene. None of 441 hypercholesterolemic subjects without mutations in the LDLR gene or in the apolipoprotein B-100 gene possessed any of the 4 mutations. Conclusion— The 4 missense mutations R46L, G106R, N157K, and R237W are associated with hypocholesterolemia and possibly increased response to statin therapy. We have screened 38 unrelated hypocholesterolemic subjects and 25 unrelated FH heterozygotes, who responded particularly well to statin therapy, for mutations in the PCSK9 gene; 15.8% of the hypocholesterolemic subjects and 8.8% of FH heterozygotes with good a response to statins possessed a missense mutation in the PCSK9 gene.