Meeting Abstract

P1-83   -   Species-specific expression of growth-regulatory genes in Anolis congeners with divergent patterns of sexual size dimorphism Cox, CL*; Logan, ML; Nicholson, DJ; Chung, AK; Rosso, AA; McMillan, WO; Cox, RM; Florida International University; University of Nevada Reno; Smithsonian Tropical Research Institute; Princeton University; Georgia Southern University; Smithsonian Tropical Research Institute; University of Virginia ccox@fiu.edu

Sexual size dimorphism is widespread in nature and typically develops through divergent growth trajectories between the sexes. In vertebrates, the growth hormone/insulin-like growth factor network (GH/IGF network) is an important regulator of growth. Growth hormone (GH) binds to growth hormone receptors (GHR) to stimulate the release of insulin-like growth factors 1 and 2 (IGF-1 and 2) which can be bound by IGF binding proteins (IGFBPs and IGF2BPs) before ultimately binding with their receptors (IGFRs). However, expression of this network is not well-characterized outside of a few model systems. Understanding sex-bias in this network across a range of taxa would give deeper insight into the mechanisms that permit the development of sex-specific body sizes. Hence, we analyzed the expression of the GH/IGF network in the liver and muscle of the male-larger brown anole lizard (Anolis sagrei) and its congener, the sexually monomorphic slender anole (Anolis apletophallus), using comparative transcriptomics. We found that expression of the GH/IGF-1 network diverges from that of rodent models in both brown and slender anoles (e.g., IGF-2 is expressed postnatally and at higher levels than IGF-1). Additionally, expression of most components of this network were tissue-specific and tended to be most highly expressed in the liver. Finally, we uncovered alternate patterns of sex-bias in the expression of receptors, growth factors, and binding proteins between brown and slender anoles in ways that are congruent with species-specific patterns of sexual dimorphism. Our work highlights the importance of comparative transcriptomics for understanding the evolution of growth regulatory networks and further suggests that evolutionary changes in sex-biased expression of GH/IGF network genes might underlie different patterns of sexual size dimorphism.