(21/04/2014, press-release, Moscow)
DNA damage is a source of the many diseases and may cause cancer and death. However, the methods used to measure DNA damage like the popular comet assay are still too expensive and inaccessible for majority of labs.
The comet assay was first described by Ostling and Johanson in 1984 and it was based on electrophoresis when intact DNA doesn’t migrate in gel, forming the head of a comet, whereas damage-relaxed DNA loops and fragment, forming the tail. Over the past 30 years this method became increasingly popular and now researchers all over the world use fluorescence or silver staining for visualisation of DNA.
Russian scientist, Andreyan Osipov, from SRC-FMBC (Russia), and his colleagues from FRC of Pediatric Hematology, Oncology and Immunology (Russia) and Chalk River Laboratories (Canada), developed a modification to that may significantly expand the range of applications of the DNA comet assay. They demonstrated that it is possible to use the well-known Giemsa stain for high-quality visualisation in bright-field microscopy.
Giemsa stain provides for sensitivity that is comparable to SybrGreen, used in the standard method. Moreover, you can even see the difference between concentration and structure of DNA in different places in comet: color of Giemsa-stained comets varies from blue to purple.
Figure 1. Representative images of DNA comets, obtained from human peripheral blood lymphocytes, stained with SybrGreen I (a) and Giemsa (d), control non-irradiated cells.
Processing of results was made on freely avialable software from the Internet.
Figure 2. A snapshot of CASP 1.2.2 software (Š”ASPlab, Wroclaw, Poland) showing a Giemsa-stained DNA comet processed by the software. In the lower right corner, various parameters of the comet highlighted in the center window of the software, such as Olive tail moment, tail moment, % DNA in tail, etc., are displayed.
"Our modification of the standard DNA comet assay is suitable for bright-field microscopy, which is very sensitive to experimental conditions and may produce high non-specific signal, Giemsa staining is very simple and more specific to DNA", said Dr. Andreyan Osipov, head of the radiation biophysics laboratory at the Burnasyan Federal Medical Biophysical Center fo Federal Medical Biological Agency in Russia.
“I hope that Dr. Osipov’s discovery will make the DNA comet method available for the resource-constrained countries in Africa so that it yields more scientists interested in studying DNA damage and repair mechanisms and contributing to the global progress in aging research”, commented Alex Zhavoronkov, PhD, the director of the Biogerontology Research Foundation in the UK.
Overall, this method seems so ingeniously simple, that it may be suitable for low-budget labs and even high school students may use it.
The study was published in the International Journal of Molecular Science, and is freely available as an Open Access publication.
DNA Comet Giemsa Staining for Conventional Bright-Field Microscopy
Osipov A, Arkhangelskaya E, Vinokurov A, SmetaninŠ° N, Zhavoronkov A, Klokov D. International Journal of Molecular Sciences. 2014; 15(4):6086-6095.
Open Access: http://www.mdpi.com/1422-0067/15/4/6086
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