Dr. Susan Balenger

Circulating levels of adrenal glucocorticoids and gonadal steroids, and interactions between these hormones, are remarkably variable across vertebrates, but the genetic underpinnings giving rise to this diversity are poorly understood. This study examines endocrine regulation in polyploids to understand how associated changes in gene copy number (i.e., gene dosage) contribute to this extraordinary diversity. Polyploidization and associated changes in gene dosage can dramatically influence the evolution of the phenotype by altering gene expression patterns and/or by increasing gene mutation rates, but how polyploidization contributes to modifications in hormonal regulation remains largely unstudied. This project examines regulation of adrenal glucocorticoids and gonadal steroids in three natural tetraploid gray treefrog lineages and their diploid ancestor to understand how polyploidization impacts endocrine control. By characterizing hormone levels and interactions between the hypothalamic-pituitary-adrenal/interrenal and hypothalamic-pituitary-gonadal axes, comparing steroid receptor and binding protein mRNA expression levels and sequences, and examining steroid binding protein levels and kinetics in diploid and tetraploid treefrogs, this study will elucidate how changes in gene dosage through polyploidization impact hormonal regulation.