Monogenic hypercholesterolaemias--an evaluation of apolipoprotein B100 and LDL receptor gene polymorphisms

Normally the N-terminal domain of the LDL receptor (LDLR) binds to low-density lipoprotein through apolipoprotein B100. Mutations within the LDL receptor and/or apolipoprotein B-100 genes compromising this process may lead to congenital monogenic hypercholesterolaemias known as familial hypercholesterolaemia or familial defective apolipoprotein B-100. These diseases are inherited as autosomal dominant traits.

To search for LDLR and apoB100 gene mutations in a Polish population of patients with hypercholesterolaemia and to determine their types and locations. An attempt was also made to evaluate the influence of identified gene mutations on the modification of protein product sequence and the severity of its functional impairment.

LDLR and apoB100 gene analyses using PCR, SSCP and automated sequencing techniques were performed in 190 hypercholesterolaemic patients. Flow cytometry was used to measure the influence of Cys152Trp mutation in the LDLR gene on ligand binding and internalisation. The OLA method was used for the preparation of adequate genetic markers allowing rapid detection of one of the most deleterious mutations of the apoB100 gene.

Three brand new mutations, not reported so far, have been detected--Pro2712Leu and Ile3532 in the apoB100 gene, and Cys347Ser in the LDLR gene--and numerous changes in the nucleotide sequence of the LDL receptor gene have been confirmed. The observations of functionality of the mutated receptor gene with flow cytometry suggested the dysfunction of LDLR due to Cys152Trp polymorphism reported in many studies.