Freeze-induced alterations of translatable mRNA populations in wood frog organs

To investigate the roles that gene expression and new protein synthesis pla y in freezing survival by the wood frog, Rana sylvatica, we compared the in vitro translation products made from mRNA isolated from six tissues (liver , brain, heart, muscle, kidney, gut) of control (5 degrees C), frozen (24 h at -2.5 degrees C), and thawed (24 h at 5 degrees C after 24 h frozen) fro gs. [S-35]Methionine-labeled proteins were separated by sodium dodecyl sulf ate-polyacrylamide gel electrophoresis and located by fluorography. Results indicated specific changes in the translatable populations of mRNA in tiss ues of freezing-exposed frogs that were largely reversed upon thawing. Diff erential protein expression was greatest in the comparison of liver from co ntrol versus frozen frogs with proteins ranging from 45 to 14.8 kDa identif ied as enhanced or unique to the frozen state. One unique protein appeared in skeletal muscle (116 kDa) of freeze-exposed frogs while another (52.5 kD a) was enhanced. Analysis of brain and heart each revealed the presence of one protein unique to the frozen state in each (58.9 and 5.9 kDa, respectiv ely) whereas no change in the pattern of in vitro translation products was seen in gut (stomach + intestine combined) or kidney between the three expe rimental states. These freeze-induced alterations in the populations of tra nslatable mRNA suggest that changes in the complement of specific proteins underlie various adaptive responses that contribute to the freezing surviva l of this amphibian. (C) 1999 Academic Press.