The human apolipoprotein L gene cluster: Identification, classification, and sites of distribution

We report the cloning of a new gene family encoding six apolipoprotein L (a poL-I to -VI) proteins. The genes were identified as a cluster spanning a r egion of 619 kb on chromosome 22. Each apoL was found to share significant identity in its predicted amphipathic alpha helices while phylogenetic tree mapping showed the genes to be evolutionarily conserved. Tissue distributi on by semiquantitative PCR revealed expression in all tissues, but consiste ntly higher levels in the placenta were observed, except for apoL-V, which had a restricted expression. A comparison of tissue distribution with apoA- I, the major structural component of high-density lipoprotein, suggests tha t the apoL proteins may play a general and fundamental role in lipid bioche mistry. In situ hybridization for expression of apoL-I in the placenta reve aled expression throughout this tissue. The pathological expression of the apolipoproteins during pregnancy is implicated in fetal growth retardation, preeclampsia, and the onset of adult atherosclerosis. (C) 2001 Academic Pr ess.