Isolation of a cDNA clone for chick intestinal apolipoprotein AI (Apo-AI) and its use for detecting apo-AI mRNA expression in several chick tissues.

Three cDNA clones for chick apolipoprotein AI (Apo-AI), the major protein component of plasma high-density lipoproteins, have been isolated. The identity of the clones has been established first by screening a cDNA library in the pEX1 expression vector with anti-Apo-AI antibodies, second by Western blot analysis of the proteins expressed by positive clones. The use of the clone containing the largest, presumably full-size, cDNA insert (apo5C12) in molecular hybridization experiments confirms that apo-AI mRNA is expressed mainly in chick small intestine and liver. Furthermore, we provide evidence that brain, heart and skeletal muscle also synthesize significant amounts of apo-AI mRNA. The Southern-blot hybridization pattern of the restriction-enzyme-digested chick DNA with the apo5C12 DNA is consistent with there being a single copy of the apo-AI gene.