Canine leptin: cDNA cloning, expression and activity of recombinant protein

Leptin, the product of the ob gene, is one of the key molecules for the regulation of appetite and whole-body energy balance, and thereby for the pathogenesis of obesity. In an attempt to clarify the roles of leptin in obesity and/or related diseases in companion animals, canine leptin c DNA was cloned by amplifying reverse-transcriptase products of RNA extracted from the adipose tissue of the beagle. A c DNA clone of about 3 kbp contained a 501 bp open reading frame coding a 167-amino acid protein with a 21-amino acid signal peptide. The sequence of a 146-amino acid mature leptin was more than 79 per cent identical to those of other mammals. Northern blot analysis revealed abundant expression of leptin m RNA in adipose tissue, but not in other tissues, in adult beagles. When Chinese hamster ovary cells expressing the rat leptin receptor were stimulated with recombinant canine leptin produced by E. coli, some intracellular signal transduction proteins were phosphorylated, indicating that the recombinant leptin was biologically active. The data reported herein will be helpful for further studies of leptin of the dog in health and disease.