ANALYSIS OF NOVEL APOLIPOPROTEIN-B MUTATIONS USING A MODIFIED U937 CELL-LINE LDL BINDING ASSAY

The U937 myelomonocyte proliferation assay can be used to detect patie nts with familial defective apolipoprotein B-100 (FDB). Previous studi es have employed electronic cell counting to assess cell proliferation . We simplified the assay using H-3-thymidine incorporation DNA analys is to measure cell growth. We tested the modified method by analyzing the effects of different concentrations of native low density lipoprot eins (LDL), methylated LDL, as well as LDLs obtained from patients wit h FDB on cell growth. Methylation of LDL to various degrees reduced ce ll proliferation correspondingly, and LDLs obtained from FDB patients decreased cell growth confirming that the modified method was able to detect binding defective species of LDL. We applied this method to ana lyze three novel apoB polymorphisms recently characterized in this lab oratory (apoB His1896-->Arg, apoB Asn1887-->Ser, apoB Ala4454-->Thr), which did not significantly alter U937 cell proliferation. Our results show that this simplified assay can be used for screening for LDL var iants with defective binding.