Structure and expression of the mouse apolipoprotein C2 gene.
Three cDNA clones containing the mouse apolipoprotein C2 (Apoc2) gene were isolated from a mouse liver cDNA library. The inserts from two cDNA clones were 500 bp in size while the insert from the third clone was unexpectedly large, 962 bp. All three clones contained a single open reading frame encoding apoC2. The exon-intron structure of the mouse Apoc2 gene was determined by sequence analysis. Northern blotting and primer extension analysis of mouse RNA showed that the major liver transcript is 500 bp in size and is encoded by four exons. Transcripts for Apoc2 were found in fetal liver, adult liver, intestine, and peritoneal macrophages. The largest cDNA clone, mAPOC2c4, contained an additional 440 bp at the 5' end that are evolutionary conserved between man and mouse. These additional sequences are encoded by two exons located 5' to the major liver start site. Although the larger transcript could not be detected by Northern blot analysis, products resulting from an upstream transcription initiation site were detected in the liver using RT-PCR analysis. The sizes of the RT-PCR products are consistent with alternative splicing.