Apolipoprotein C-II deficiency: identification of a structural variant ApoC-II Padova.

Apolipoprotein(apo) C-II DNA, RNA and protein from a patient with a familial deficiency of apoC-II were evaluated and compared to normal individuals. No major defect of the apoC-II gene could be detected by Southern blot hybridization. Northern and slot blot analyses of total liver RNA documented normal levels of a normal sized apoC-II mRNA. Immunohistochemical studies of the liver of the apoC-II deficient patient revealed a normal to slightly elevated intracellular content of the C-II apolipoprotein. Plasma apoC-II was 3 to 5% of normal apoC-II levels and exhibited abnormal electrophoretic mobility on two dimensional gel electrophoresis and immunoblotting. We postulate that at the molecular level, the deficiency of apoC-II in the plasma of this patient results from a structural defect in the coding portion of the apoC-II gene leading to either defective secretion of cellular apoC-II or increased catabolism of a structurally defective apoC-II in plasma.