Publication Spotlight: Perish the Thawed? Undergraduates Making an Impact

A recent publication in PLOS One highlighted the work by Ocean Genome Legacy (OGL) scientists and undergraduate co-ops (among others) as they discovered an improved method of preserving DNA during extraction from frozen tissues. 

DNA sequencing is such a valuable tool for information gathering in the biosciences. Although there have been many techniques developed to amplify and sequence\ degraded DNA, it is still best to have high molecular weight (HMW) for optimal sequencing results. 

This is one of the reasons why Messner, et. al.’s paper is so intriguing. Published in PLOS One, “Perish the thawed? EDTA reduces DNA degradation during extraction from frozen tissue” describes the authors’ efforts to determine a simple and effective method to preserve DNA, particularly HMW DNA, while extracting DNA from frozen samples. 

Although cryopreservation is the best method for preserving samples, that protection disappears during typical liquid-based DNA extraction procedures. It is possible to grind the frozen tissues before extraction however grinding methods are difficult to perform, involve dangerous substances (for example liquid nitrogen) and still leave the sample open to possible thawing.

Messner, et. al. investigated the use of ethylenediaminetetraacetic acid (EDTA) and ethanol (EtOH) as preservatives for frozen tissues. EtOH is commonly used for storage, or field collection of fresh tissue, however it is flammable and subject to regulations.  EDTA is a component of a number of preservative solutions and is nonflammable, making it more easily handled.

DNA samples from ten marine species were extracted after treatment during thawing with either of the two potential preservatives. Nine out of ten EDTA-treated samples showed significant improvement in the average %HMW DNA or yield of HMW DNA when normalized by tissue weight compared to the DNA extracted from untreated frozen samples. EtOH-treated samples’ DNA yields and quality were not significantly improved over yields and quality of the DNA from non-treated samples, and in fact were sometimes worse. The authors examined samples from different cryopreservation methods and found similar EDTA treatment results.  PCR and sequencing results also supported the use of EDTA during thawing to improve DNA extraction. 

These results suggest that EDTA treatment during thawing can greatly aid investigators by allowing for safer and less expensive DNA extraction methods—both in the lab and in the field. The authors note that only marine tissues were examined, and believe that future investigation into other types of tissues could be valuable given the world-wide diversity of frozen research collections.

It's great to see undergraduates making an impact on science world-wide!

E. Messner, L. Becker. M. L. DeSanctis, E. A. Soranno, R. Pianka, C. Pierce, M. Johnson, R. F. Poulin, H. J. Appiah-Madson, D. L. Distel. Perish the thawed? EDTA reduces DNA degradation during extraction from frozen tissue. PLoS One 20(6): e0321872. https://doi.org/10.1371/journal.pone.0321872