Abifadel et al. (2003) carried out positional cloning using the family in which linkage was originally identified (Varret et al., 1999) and 23 French families in whom involvement of LDLR and APOB had been excluded as the site ... Abifadel et al. (2003) carried out positional cloning using the family in which linkage was originally identified (Varret et al., 1999) and 23 French families in whom involvement of LDLR and APOB had been excluded as the site of causative mutations. The critical region was found to contain 41 genes, including PCSK9 (607786). They identified PCSK9 mutations (607786.0001 and 607786.0002) in 3 French families with hypercholesterolemia. By mutation screening of genes in the chromosome 1p32 region in patients with familial hypercholesterolemia from the Utah pedigree studied by Hunt et al. (2000), Timms et al. (2004) identified a D374Y (607786.0003) mutation in the PCSK9 gene. In 3 of 64 African American subjects with low plasma levels of low density lipoprotein cholesterol (LDLCQ1), Cohen et al. (2005) identified a nonsense mutation (Y142X; 607786.0004) in the PCSK9 gene.