Meeting Abstract

P2.7  Tuesday, Jan. 5  Steller sea lion (Eumetopias jubatus) leptin cDNA Sequence Homology RICHMOND, J.P.*; REA, L.D.; ZINN, S.A.; University of Connecticut, Storrs; Alaska Department of Fish and Game, Fairbanks; University of Connecticut, Storrs julie.richmond@uconn.edu

Increased circulating concentrations of leptin are observed with increased adiposity in most mammalian species, but this relationship is not clear in pinnipeds. This suggests that either leptin may be differentially regulated in pinnipeds or that contrasting results may be due to reduced sensitivity of multi-species assays used to quantify hormone concentrations. Either hypothesis necessitates an understanding of the sequence homology of leptin for experimentation. The objective of this research was to sequence leptin cDNA in Steller sea lions and determine the homology among various mammalian species. Adipose tissue was collected from free-ranging Steller sea lions (n=3). Total RNA was isolated from adipose tissue (Promega SV Total RNA Isolation), and quantified by spectrophotometric (NanoDrop 1000) and electrophoretic methods (Experion RNA StdSens Analysis). RNA was reverse transcribed to cDNA (Promega RT System) and amplified with canine leptin primers using standard PCR methods. The cDNA product was sequenced using 3130XL Genetic Analyzer. The cDNA sequence of Steller sea lions is 92% homologous with dog, but shares only 84% homology with mouse. This difference in cDNA results in an inferred Steller sea lion protein sequence that shares approximately 89% and 74% homology with dog and mouse, respectively. Due to the differences in cDNA sequence between mouse and sea lions careful interpretation of results from studies that have used mouse based immunoassays must be employed. Results using mouse based immunoassays may be inaccurate due to variability in protein structure resulting in poor assay accuracy. Based on inferred protein structure, if heterologous assays must be used, antisera to canine leptin may have better potential for accurate assessment of sea lion leptin.