BACKGROUND: Familial hypercholesterolemia (FH) is an autosomal disorder 
associated with elevated plasma low density lipoprotein (LDL) levels leading to 
premature coronary heart disease (CHD). As a result of long-term hyperlipemia, 
FH patients will present endarterium thickening and artherosclerosis. In the 
present study we scanned the related gene of a clinically diagnosed autosomal 
genetic hypercholesterolemia family for the possible mutations and established 
eukaryotic expression vector of mutation of proprotein convertase 
subtilisin/kexin type 9 (PCSK9) gene with gene recombination technique to 
investigate the contributions of the variation on low density lipoprotein 
receptor (LDL-R) metabolism and function alternation.
METHODS: Mutation detection was conducted for LDL-R, apolipoprotein B(100) 
(apoB(100)) and PCSK9 gene with nucleotide sequencing in a Chinese FH family. 
The full-length cDNA of wild type PCSK9 gene (WT-PCSK9) was obtained from 
Bel-7402. Site mutagenesis was used to establish the recombinant eukaryotic 
expression vector carrying pathogenic type of PCSK9 gene and the inserted 
fragment was sequenced. With the blank vector as control, liposome transfection 
method was used to transfect the Bel-7402 cells with recombinant plasmid. The 
expression of LDL-R mRNA was examined by RT-PCR. PCSK9 and the expression of 
LDL-R protein were determined by Western blotting.
RESULTS: The G-->T mutation at the 918 nucleotide of PCSK9 gene resulted in the 
substitution of the arginine by a serine at the codon 306 of exon 6. After 
sequencing, it was confirmed that the inserted fragment of established 
expression vector had correct size and sequence and the mutant was highly 
expressed in Bel-7402 cells. There was no significant variation in the levels of 
LDL-R mRNA. LDL-R mature protein was decreased by 57% after the cells were 
transfected by WT-PCSK9 plasmid. Mature LDL-R was significantly decreased by 12% 
after the cells were transfected by R306S mutant as evidenced by gray scale 
scanning, suggesting that the new mutant R306S can significantly decrease the 
expression of mature LDL-R protein.
CONCLUSIONS: A novel missense mutation of PCSK9 gene, R306S, was found and the 
eukaryotic expression vectors of mutant and wild-type of PCSK9 gene were 
established. There was no significant variation in the levels of LDL-R mRNA. The 
R306S mutation could significantly lead to the decrease of LDL-R mature protein 
expression, which might be the pathogenic gene of the FH family.