Meeting Abstract

P2.8  Tuesday, Jan. 5  Genomic characterization of two leptin genes and a leptin receptor gene in the Green Anole, Anolis carolinensis BOORSE, GC*; LIBBON, JV; Arizona State University, West Campus graham.boorse@asu.edu

Leptin is a type-I cytokine hormone secreted primarily by adipose tissue that is central to regulating food intake, energy balance and reproduction in mammals. Our knowledge of leptin evolution has been impacted by limited success in identifying leptin orthologs from vertebrate groups outside of mammals and fish. Debate over the validity of chicken leptin gene sequence has further clouded the molecular evolution of leptin. By analyzing the A. carolinensis genome, we have identified two leptin genes (LepA and LepB) and one leptin receptor (LepR) gene. Like fish and amphibian leptins, both lizard leptins show low amino acid similarity (~38%) but do show nearly identical predicted tertiary structures to mammalian leptins. Lizard LepA and LepB exhibited genomic synteny with human Lep (7q21) based on the limited gene arrangement information available from the current version of the Anole genome suggesting both are orthologous to human leptin. Molecular cloning of LepA by RT-PCR confirmed it was expressed in brain and spinal cord. Similar techniques failed to demonstrate expression of LepB in any tissue examined thus far suggesting this gene may not be expressed or expressed in low amounts. Using RT-PCR we have identified a 741bp fragment from testis with a deduced amino acid sequence that exhibits 57% similarity to human LepR; molecular phylogenetic analyses in conjunction with synteny mapping have clearly identified this molecule as the lizard LepR ortholog. Tissue distribution of leptin and receptor genes by RT-PCR and generation of full length clones by RACE-PCR are currently underway. Our characterization of lizard leptin and its receptor provides addition insight into our understanding of the structural and functional evolution of this important hormone.