Identification of Apolipoprotein E Guangzhou (Arginine 150 Proline), a New Variant Associated with Lipoprotein Glomerulopathy

Abstract

Background/Aims: Lipoprotein glomerulopathy (LPG) is a rare disease characterized by thrombus-like substances in markedly dilated glomerular capillaries and elevated plasma levels of apolipoprotein E (apoE). Previous studies have shown that genetic disorders of apoE may contribute to the pathogenesis of LPG, but LPG may not be caused by apoE gene mutations in Chinese patients. This study investigated the association of a new variant of apoE with LPG in a Chinese family. Methods: The apoE gene in a family with 4 LPG patients was sequenced. The polymerase chain reaction product of coding region of apoE exon 4 was cloned into pMD 18-T vector and then sequenced. Results: A novel point mutation in exon 4 of the apoE gene was identified in all 4 LPG patients and 1 asymptomatic family member. Sequence analysis confirmed a nucleotide G to C point mutation in exon 4 (base 308) of the apoE gene in all patients and the asymptomatic family member. This missense mutation denotes amino acid substitution of the proline residue for arginine residue at position 150 of apoE. Those patients were all heterozygotes with apoE Guangzhou. One of 2 grandsons was a heterozygous carrier of apoE Guangzhou, although he did not have proteinuria. Conclusion: The results of this study suggest that apoE (arginine 150 proline) is a novel apoE variant that etiologically related to LPG. This variant (apoE Guangzhou) may cause a marked molecular conformational change of the apoE and thus impair its binding ability to lipids.