Vertebrate freeze tolerance: Molecular studies of signal transduction and gene expression

Various amphibians and reptiles have the extraordinary ability to endure the freezing of body fluids while overwintering. In studies with the wood frog, Rana sylvatica, we continue to explore new facets of vertebrate freeze tolerance. New studies have analyzed modifications of wood frog insulin and the controls on protein kinase A and protein phosphatase-1 that regulate glycogen metabolism in order to determine how normal homeostatic control over glucose is overridden to allow glucose to reach the extreme concentrations needed for cryoprotection. The roles of mitogen-activated protein kinases in mediating cell responses to freeze/thaw are also being assessed. Other studies are using cDNA library screening to analyze freeze-induced gene expression. Novel results include the identification of genes, protein products and cell functions that have never before been implicated in natural freezing survival.