Meeting Abstract
The Insulin and Insulin-like Signaling (IIS) network regulates cellular processes including pre- and post-natal growth, cellular development, wound healing, reproduction, and longevity. Recent work at the sequence level has demonstrated that the IIS network has been rapidly evolving in reptiles relative to mammals, raising questions about how the transcriptional regulation of the IIS network may have also evolved. Here we compare the expression of the top regulators of the IIS network —IGF hormones (IGF1, IGF2), IGF binding proteins (IGFBP1, IGFBP2, IGFBP3, IGFBP4, IGFBP5) and the IGF1 receptor (IGF1R) — in a lizard to what is known in rodents. IGFBPs regulate the circulation of IGF hormones, facilitating tissue-specific binding of these hormones to their receptors, activating the network. Despite their importance on the physiology of vertebrates, the specific functions of each IGFBP and each IGF hormone is relatively unknown in reptiles. To address this, we first assay the presence of expression of IGFBPs, the IGF hormones, and IGF1R across tissues and ages (embryo to adulthood). In adults, both IGF1 and IGF2 are expressed in all tissues, but the ratio of IGF1 to IGF2 changes significantly with age. IGFBP3-IGFBP5 are expressed ubiquitously across tissue in adults, but IGFBP2 is not expressed in the heart and IGFBP1 is only expressed in the liver. Second, we develop and employ a multiplex qPCR assay for absolute quantification of IGF1, IGF2, and the IGF1R gene expression in liver, brain, skeletal muscle, and gonadal tissue at 7 ages, emphasizing early life stages. We will contrast these results to patterns found in mammals. The data collected in this study is essential for future studies of the IIS network in reptiles, as well as understanding the relative roles of IGF1 and IGF2 in development of the Anolis lizard.
