LINKAGE OF FAMILIAL COMBINED HYPERLIPIDEMIA TO CHROMOSOME 1Q21-Q23

More than half of the patients with angiographically confirmed prematu re coronary heart disease (CHD) have a familiar lipoprotein disorder(1 ). Familial combined hyperlipidaemia (FCHL) represents the most common genetic dyslipidemia with a prevalence of 1.0-2.0% (refs 2,3). FCHL i s estimated to cause 10-20% of premature CHD (ref. 1) and is character ized by elevated levels of cholesterol, triglycerides, or both(3,4). A ttempts to characterize genes predisposing to FCHL have been hampered by its equivocal phenotype definition, unknown mode of inheritance and genetic heterogeneity. In order to minimize genetic heterogeneity, we chose 31 extended FCHL families from the isolated Finnish population( 5) that fulfilled strictly defined criteria for the phenotype status. We performed linkage analyses with markers from ten chromosomal region s that contain lipid-metabolism candidate genes. One marker, D1S104. a djacent to the apolipoprotein A-II (APOA2) gene on chromosome 1, revea led a lod score of Z=3.50 assuming a dominant mode of inheritance. Mul tipoint analysis combining information from D1S104 and the neighbourin g marker D1S1677 resulted in a lod score of 5.93. Physical positioning of known genes in the area (APOA2 and three selectin genes) outside t he linked region suggests a novel locus for FCHL on 1q21-q23. A second paper in this issue (Castellani et al.) reports the identification of a mouse combined hyperlipidaemia locus in the syntenic region of the mouse genome(6), thus further implicating a gene in this region in the aetiology of FCHL.