Screening for mutations in exon 4 of the LDL receptor gene in Thai subjects with primary hypercholesterolemia: detection of a novel mutation D151Y by PCR-CFLP.

A mutation in low density lipoprotein (LDL) receptor gene causes an autosomal codominant disorder namely familial hypercholesterolemia (FH). Mutations in the LDL receptor gene are very heterogeneous at the DNA levels, occurring in all 18 exons of the gene. However, exon 4 has been found to be the hot spot for mutational events. In this study DNA from 45 Thai subjects with primary hypercholesterolemia was screened for mutations in the hot spot exon 4. The DNA samples were amplified by Polymerase Chain Reaction (PCR) and screened for mutation by Cleavase Fragment Length Polymorphism (CFLP) technique. Identification of mutation was performed by direct sequencing of PCR product. From this screening, one female patient was found to be heterozygous for a novel mutation which was due to a G to T transversion at nucleotide 514. This transversion would change the species-conserved amino acid at codon 151 from charged R group aspatic (GAC) to uncharged R group tyrosine (TAC), termed D151Y. From the same screening strategy, we found that this mutation was absent in 33 healthy normolipidemic subjects. In this index subject, Arg 3500 Gln mutation in apo B-100 gene, causing hypercholesterolemia namely familial defective apo B-100 (FDB), was not found. Therefore, hypercholesterolemia in this index subject was possibly caused by the D151Y mutation in the LDL receptor gene.

Molecular examination of GH gene deletion in familial growth hormone deficiency.

The human growth hormone gene (GH gene) from nine members of a family with familial growth hormone deficiency was examined. The patients were diagnosed as having growth hormone deficiency clinically and by response to hormonal treatment. PCR amplification was carried out using total DNA extracted from leukocytes. The flanking regions of the GH gene which are highly homologous were amplified by one pair of primers. PCR products of 1900 bp and 1919 bp were obtained. By using the combination of restriction enzymes BgII, HaeII and SmaI to digest these PCR products, the various sizes of GH gene deletion can be detected. None of the possible deletions was found in these patients and their relatives by either PCR or Southern blot analysis.