Liam Hawkins, M.Sc. Biology 2016

Histone methylation in the freeze-tolerant wood frog, Rana sylvatica


The wood frog, Rana sylvatica, has developed numerous adaptations to survive days with up to 65% of its body fluid frozen. One such adaptation is to reduce their metabolic rate, employing only those processes needed to survive until temperatures rise. The establishment of this hypometabolic state is mediated by transcriptional regulation that is elicited in part by histone methylation, however this has yet to be explored in the context of metabolic rate depression and freeze tolerance. This thesis provides the first characterization of histone methyltransferases (HMTs) and the histone and non-histone proteins they methylate in the wood frog. Transcriptionally permissive histone residues (H3K4me1 and H3K27me1) were found to decrease during freezing in skeletal muscle while those that silence transcription (H3K9me3 and H3K36me2) were maintained, whereas differential levels of histone residues were seen in liver. These findings suggest a novel role for HMTs in freeze tolerance.