Use of the denaturing gradient gel electrophoresis (DGGE) method for mutational screening of patients with familial hypercholesterolaemia (FH) and Familial defective apolipoprotein B100 (FDB)

Familial hypercholesterolaemia (FH) and Familial defective apolipoprotein B100 (FDB) are autosomal dominant inherited diseases of lipid metabolism caused by mutations in the low density lipoprotein (LDL) receptor and apolipoprotein B 100 genes. FH is clinically characterised by elevated concentrations of total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C), presence of xanthomata and premature atherosclerosis. Both conditions are associated with coronary artery disease but may be clinically indistinguishable. Seventy-two (72) FH patients were diagnosed based on the Simon Broome's criteria. Mutational screening was performed by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). Positive mutations were subjected to DNA sequencing for confirmation of the mutation. We successfully amplified all exons in the LDL receptor and apo B100 genes. DGGE was performed in all exons of the LDL receptor (except for exons 4-3', 18 and promoter region) and apo B100 genes. We have identified four different mutations in the LDL receptor gene but no mutation was detected in the apo B 100 gene. The apo B100 gene mutation was not detected on DGGE screening as sequencing was not performed for negative cases on DGGE technique. To our knowledge, the C234S mutation (exon 5) is a novel mutation worldwide. The D69N mutation (exon 3) has been reported locally while the R385W (exon 9) and R716G (exon 15) mutations have not been reported locally. However, only 4 mutations have been identified among 14/72 patients (19.4%) in 39 FH families. Specificity (1-false positive) of this technique was 44.7% based on the fact that 42/76 (55.3%) samples with band shifts showed normal DNA sequencing results. A more sensitive method needs to be addressed in future studies in order to fully characterise the LDLR and apo B100 genes such as denaturing high performance liquid chromatography. In conclusion, we have developed the DNA analysis for FH patients using PCR-DGGE technique. DNA analysis plays an important role to characterise the type of mutations and forms an adjunct to clinical diagnosis.