Baboon lipoprotein lipase: cDNA sequence and variable tissue-specific expression of two transcripts

We have isolated two lipoprotein lipase (LPL)-encoding cDNA (LPL) clones from a baboon cardiac cDNA library, one of which spans a region from nucleotide (nt) 705 of the coding sequence to the poly(A) tail (2.8 kb). We used reverse transcription followed by PCR (RT-PCR), and anchor-ligated rapid amplification of cDNA ends (RACE) to amplify the remaining 5' region of the LPL transcript. Sequence comparisons reveal that the baboon nt sequence is 95% identical to the human cDNA sequence (ranging from 97.5 to 92.7% in the coding and noncoding regions, respectively). Less than 2% of nt substitutions cause changes between baboon and human amino acid (aa) sequences. The aa in the catalytic triad residues, the heparin-binding site in exon 6, as well as aa in positions where missense mutations cause LPL deficiency, are identical in baboons and humans. Characterization of the tissue-specific expression of LPL using Northern blots of total RNA showed that spinal cord expressed the most LPL transcripts of all baboon tissues examined. Like humans, baboons have two transcript sizes of approx. 3.6 and 3.4 kb in most tissues that express LPL, and sequencing of the 3' untranslated region (UTR) shows this is due to two polyadenylation sites. In contrast, only the larger 3.6-kb transcript is detected in RNA isolated from central nervous system (CNS) tissues. We used RT-PCR to show that the polyadenylation signal that produces the 3.4-kb message is present in CNS LPL transcripts, but is not utilized.