Methyl Epigenetic Mechanisms in the Freeze-Tolerance Response of Rana Sylvatica Nervous Tissue

Wood frog freeze tolerance is a classic example of metabolic rate depression (MRD), which facilitates reprioritization of minimal anaerobic resources to pro-survival pathways. Global gene expression is consequentially suppressed due, in part, to transcriptional controls, yet specific mechanisms have received little attention. Methylation of DNA and histone lysine residues are common epigenetic mechanisms associated with control of transcription and thus are implicated in MRD. However, preliminary findings appear tissue- and species-specific while research into nervous tissues is lacking. This thesis tracks the expression/activity of key methyl epigenetic modifiers and selected targets across the wood frog freeze-thaw cycle and associated sub-stresses. This thesis provides strong evidence for H3K9 and DNA hypomethylation during brain freeze recovery, largely correlated with expression of catalyzing enzymes. Non-histone roles are also suggested. Alleviation of repressive epigenetic controls likely contribute to a resumed permissive transcriptional state and may induce the activity of essential repair pathways during thawing.