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J Comp Physiol B. 2016 Apr;186(3):333-42. doi: 10.1007/s00360-016-0960-x. Epub 2016 Feb 3.

The role of DNA methylation during anoxia tolerance in a freshwater turtle (Trachemys scripta elegans).

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Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada.
Department of Biology, Department of Chemistry, Canada Research Chair in Molecular Physiology, Institute of Biochemistry, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada.


Oxygen deprivation is a lethal stress that only a few animals can tolerate for extended periods. This study focuses on analyzing the role of DNA methylation in aiding natural anoxia tolerance in a champion vertebrate anaerobe, the red-eared slider turtle (Trachemys scripta elegans). We examined the relative expression and total enzymatic activity of four DNA methyltransferases (DNMT1, DNMT2, DNMT3a and DNMT3b), two methyl-binding domain proteins (MBD1 and MBD2), and relative genomic levels of 5-methylcytosine under control, 5 h anoxic, and 20 h anoxic conditions in liver, heart, and white skeletal muscle (n = 4, p < 0.05). In liver, protein expression of DNMT1, DNMT2, MBD1, and MBD2 rose significantly by two- to fourfold after 5 h anoxic submergence compared to normoxic-control conditions. In heart, 5 h anoxia submergence resulted in a 1.4-fold increase in DNMT3a levels and a significant decrease in MBD1 and MBD2 levels to ~30 % of control values. In white muscle, DNMT3a and DNMT3b increased threefold and MBD1 levels increased by 50 % in response to 5 h anoxia. Total DNMT activity rose by 0.6-2.0-fold in liver and white muscle and likewise global 5mC levels significantly increased in liver and white muscle under 5 and 20 h anoxia. The results demonstrate an overall increase in DNA methylation, DNMT protein expression and enzymatic activity in response to 5 and 20 h anoxia in liver and white muscle indicating a potential downregulation of gene expression via this epigenetic mechanism during oxygen deprivation.


Anoxia; DNA methyltransferases; Epigenetics; Metabolic rate depression; Methyl-binding proteins; Trachemys scripta elegans

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