Nonsynonymous natural genetic polymorphisms in the bovine leptin gene affect biochemical and biological characteristics of the mature hormone1

Abstract

Leptin (LEP) is a cytokine-like hormone proven to be involved in diverse biological processes. In livestock, it regulates feed intake, BW homeostasis, and energy balance, among other traits. Natural nonsynonymous genetic polymorphisms in the ovine leptin (oLEP) alter the biochemical and physiological characteristics of its gene products. Here we studied in vitro and in vivo the biochemical and physiological characteristics of recombinant hormones representing the oLEP and bovine leptin (bLEP) reference sequences of wild-type (WT) leptins (GenBank accession No. U84247 and U50365, respectively), oLEP and bLEP recombinant muteins carrying the R4C mutation, and oLEP recombinant hormones carrying the A59V and Q62R mutations, which were detected in bLEP. All proteins were purified to homogeneity as monomers and formed 1:1 molar ratio complexes with the chicken leptin-binding domain (LBD). Surface plasmon resonance experiments revealed that all protein variants exhibit reduced (P < 0.05) affinity to chicken (ch) and human (h) LBD compared with the WT oLEP and bLEP recombinant proteins. The ovine and bovine R4C muteins exhibited significantly (P < 0.05) greater induction of cell proliferation in a Baf/3 cell line bioassay, despite lower affinity toward both hLBD and chLBD. Intra-third cerebral ventricle infusion of oLEP and its 3 muteins in sheep resulted in reduced feed intake. However, the 3 tested muteins had a decreased (P < 0.05) inhibitory effect than the WT LEP. It was concluded that natural genetic polymorphisms in the bLEP are associated with variation in the biochemical and physiological properties of the protein.