Characterization of two new human apolipoprotein A-I variants: apolipoprotein A-I Tsushima (Trp-108-->Arg) and A-I Hita (Ala-95-->Asp).

Two unrelated subjects with new variants of apolipoprotein (apo) A-I were found during screening with isoelectric focusing (IEF) gel analysis. In the first case, apo A-I Tsushima, sequencing following amplification by the polymerase chain reaction (PCR) revealed a residue 108 missense mutation (TGG-->CGG, Trp-->Arg) in exon 4. The proband of apo A-I Tsushima was heterozygous for this mutation. The second case, apo A-I Hita, revealed a residue 95 missense mutation (GCC-->GAC, Ala-->Asp) in exon 4. The proband of apo A-I Hita was compound heterozygous with apo A-I (Ala-37-->Thr). These two subjects exhibited normal plasma concentrations of apo A-I and HDL cholesterol. In screening normal high school students (n = 198), we used a PCR-mediated site-directed mutagenesis to rapidly detect the substitution of G to A at codon 37 because the apo A-I (GC-->ACC, Ala-37-->Thr) mutation is unrelated to the charge difference on IEF. The frequency of the A allele was 0.04: the substitution G to A at codon 37 did not affect the plasma concentrations of lipids and lipoproteins.