Freeze Tolerant Frogs!

Since a lot of our posts seem to be about cool organisms and how they can be beneficial to humans, I thought about one that I was interested in a few years ago. There's an amphibian that undergoes freeze-thaw cycles due to its surrounding arctic environment and lives through it! Normally, animals would migrate to warmer climates or hibernate for the winter, but the North American wood frog (Rana sylvatica) buries in the leaves and allows itself to freeze in suspended animation. They are able to survive weeks at a time without a beating heart and brain activity. When the temperature drops, urea concentrates in the tissues and their liver produces mass amounts of glucose and packs it into the cells to prevent intracellular ice formation. When water turns into ice, it forms ice crystals, which are harmful to cells causing shrinkage and cell death. Obviously, this must be avoided in order to survive freeze thaw cycles. Therefore, the urea and glucose are used as a cryoprotectant to lower the freezing temperature in the tissues. However, it has been suggested that enduring many freeze thaw cycles could result in significant energy depletion and be fatal to the frog. Applications for this freeze tolerant ability include aiding human organ transplants and cryopreservation of whole humans.

http://voices.nationalgeographic.com/2013/08/21/how-the-alaska-wood-frog-survives-being-frozen/

http://news.nationalgeographic.com/news/2007/02/070220-frog-antifreeze.html

https://www.youtube.com/watch?v=Fjr3A_kfspM


They are able to do this with special proteins in their blood called nucleating proteins.

DNA Phenotyping

When I first started my education in forensic science, I wrote a paper about craniofacial reconstruction, which is the process of giving a face to unidentified skulls. I thought maybe I could do this because I also love to draw. My specialty is the human form,  and specifically the face because that's what people pay for. However, forensic artists can't determine the color of the skin, hair, or eyes based on features of the skull so the final product will be a black and white sketch or a beige and bald clay sculpture. Then I read about a rapidly developing field of research called DNA phenotyping and it has been one of my favorite topics since. 

DNA phenotyping uses single nucleotide polymorphisms (SNPs) found within or around genes linked to externally visible characteristics (EVCs). One gene that is commonly used as an EVC is amelogenin for sex determination of biological evidence. One of the coolest labs I got to do during graduate school was verify our own eye color via genotyping using IrisPlex, a DNA-based eye color prediction assay. IrisPlex uses six informative SNPs: MC1R, OCA2, SLC24A5, MATP (SLC45A2), ASIP, and TYR.  Then you imput the allele into a table and it gives you a predicted phenotype for blue, intermediate, and brown eye color. We were able to accurately predict everybody's eye color that did the lab so I was impressed. Now, there is a company that  does DNA phenotyping, ancestry and kinship analysis. The Snapshot Forensic DNA Phenotyping System by Parabon can generate a likely profile using DNA genotyping. This tool can be used for investigative leads when a DNA profile from an unknown sample (hopefully being from the suspect) generates no hits from the convicted offender database, as well as for missing persons, disaster victim identification, and repatriating war remains.

I strongly urge you guys to go look at the following websites. It's pretty neat!


References:

• http://hirisplex.erasmusmc.nl/ 
• https://snapshot.parabon-nanolabs.com/
• Dembinski G M, Picard C J. Evaluation of the IrisPlex DNA-based eye color prediction assay in a United States population. Forensic Science International: Genetics 9 (2014) 111-117.

Rapid DNA Analysis Systems

Rapid DNA analysis refers to a fully automated process of DNA typing, essentially a "swab in - profile out" system that only takes a couple of hours. Standard DNA typing methods take about 10 hours over several days for DNA profiling of just one sample. These traditional methods require experienced technicians and the use of several expensive instruments and commercial kits. Therefore, scientific advancements have been made to traditional protocols in order to reduce costs and the amount of time for testing. Rapid DNA systems perform a modified method of extraction, short tandem repeat (STR) amplification, and separation and detection of DNA fragments driven by active microfluidics. They also contain an on-board platform for allele calling and generating electropherograms. There are many applications for this type of system: police booking stations, border security, and human identification in mass disasters just to name a few. These systems could provide quick investigative leads, minimize laboratory backlogs, and reduce contamination issues.

There are two systems on the market right now. One is called DNAscan (GE Healthcare and NetBio) and the other is RapidHIT 200 (IntegenX). They are both able to process five samples in less than 90 minutes, but RapidHIT also includes positive and negative controls. Both systems require minimal training on account of fully automated technical capabilities. When I was doing my internship in the summer of 2013, I was able to use these instruments during a demonstration and I even got my own profile from the RapidHIT instrument. I compared it to the one that I produced in my lab and it matched!

Furthermore, there are two types of this type of analysis, rapid DNA analysis and modified rapid DNA analysis. Rapid DNA analysis generates a profile without any human intervention, whereas modified rapid DNA analysis requires human interpretation of the profile and technical review. The distinction is important because only the modified rapid DNA analysis profiles are able to be uploaded into CODIS. This database is maintained by the FBI and contains DNA profiles from convicted offenders, arrestees, and forensic unknowns. DNAscan is the first and only system approved by the FBI to upload profiles to CODIS after scientists have analyzed them.

For more information:

• https://www.fbi.gov/services/laboratory/biometric-analysis/codis/rapid-dna-analysis
• http://www.gelifesciences.com/webapp/wcs/stores/servlet/ProductDisplay?categoryId=364838&catalogId=10101&productId=71366&storeId=11787&langId=-1
• https://promo.gelifesciences.com/gl/DNASCAN-RAPID-DNA/
• https://integenx.com/products/rapid-dna/
• https://www.fbi.gov/services/laboratory/biometric-analysis/codis/codis-and-ndis-fact-sheet