Molecular cloning and characterization of angiopoietin-like protein-8 gene in pigs and its tissue-specific expression in different animals

Angiopoietin-like protein 8 (Angptl8) is a new constituent of angiopoietin-related protein family. In the present study, Landrace × Yorkshire pigs, C57BL/6 J mice, and Wistar rat were used as experimental animals. Using normal PCR, T-A cloning, RACE, and other experimental techniques, full length of porcine Angptl8 gene was cloned. Through real-time PCR, Angptl8 expression was detected in assorted tissues (kidney, heart, spleen, liver, lung, abdominal fat, and back longest muscle) of different animals. The present result showed that the full-length of porcine Angptl8 was 875 bp. Its ORF region contained 597 bp, from 21 bp to 618 bp, it had high conservation. The protein of Angptl8 had 198 amino acids. Its relative molecular mass was 21,988.3 Da. Its theoretical isoelectric point was 6.35. There was a highly hydrophobic region near the 10th amino acid site of the Angptl8 gene, while 177th and 187th were highly hydrophilic. Angptl8 protein may be not a transmembrane protein. The first to the 19th amino acids on the N-terminal were signal peptides, and the first 18th–19th amino acid sites may be the signal peptide shear site. In addition, Angptl8 in healthy pigs was mainly expressed in the liver. Its expression in heart and adipose tissue was minimum. Angptl8 of both mouse and rat was enriched in the fat and liver; mouse and rat minimum Angptl8 expression was in muscle and spleen, respectively. The present results suggest that there may exist species difference in tissue-specific expression of Angptl8.