CometImager and Metafer CometScan
Introduction
The single cell gel electrophoresis (SCGE)
assay, commonly referred to as "comet assay", allows the very sensitive
detection of DNA breakage induced by genotoxic agents at single cell level. Due to its
sensitivity and simplicity, the comet assay is commonly used as endpoint for mutagenic
testing as well as for apopotosis investigations. Under lysis conditions during the
electrophoresis step, DNA fragments as outcome of single-stranded and double-stranded
breaks migrate faster in the electric field than intact DNA. If the DNA is stained with an
appropriate fluorochrome the eluted fragments are visible as comet tail under fluorescence
microscopy conditions. The amount of DNA damage can be derived from the ratio of tail and
head (nucleus) intensities and sizes.
More detailed information on the comet assay is provided at the comet assay site by T.S. Kumaravel (www.cometassay.com).
With MetaSystems products single cell gel electrophoresis preparations can be analyzed fast and reproducible, either with the interactive Comet assay software CometImager, or with the fully automated analysis system CometScan, that is based on the scanning platform Metafer.
Comet Imager: Interactive SCGE Assay Analysis
The single cell
gel electrophoresis analysis system CometImager allows for fast and reliable,
interactive analysis of 'comets'. CometImager combines high effectiveness with
affordable hardware requirements. Image capture is controlled by the software to
assure correct exposure independent of the overall comet intensity. Comet analysis is
performed automatically, and the distinction between head and tail of the comet is made
automatically, according to threshold parameters which can be defined by the user. Results
are displayed online, e.g as histograms of comet parameters like tail moment, tail
intensity, etc. Data can be exported in suitable data formats for statistical analysis
using standard software packages. Since the comet assay requires the evaluation of many
cells per experiment the CometImager is optimized for fast routine analysis. A
user-friendly interface minimizes the number of interactions, while the full documentation
of any step provides high reliability of the results.
Metafer CometScan: Automatic SCGE Assay Analysis
The automatic CometScan
module, a software for the multipurpose scanning platform Metafer, offers the possibility of completely unattended
evaluation of SCGE preparations. It is therefore especially useful for laboratories using
the comet assay as routine diagnostic method, and having a high number of slides per day
to analyse. Connected to a motorized fluorescence microscope, the software controls all
aspects of the scan including integration time, slide stage movement and fluorescence
filters. CometScan automatically detects cells, measures relevant comet
features like intensity of head and tail, comet shape, tail moment, etc., and stores an
image of each cell in a gallery. Overlays document thresholds and the borderlines
between head and tail. Selected cell features such as the measured intensities can be
displayed in the image corners.
During the scan, histograms of comet parameters are displayed and updated in real time. After the scan, the operator can check the analyzed cells in the gallery. Unsuitable cells can be rejected, questionable cells can be relocated under the microscope with a simple mouse click. With up to 1000 analyzed cells per hour CometScan provides unprecedented high throughput mutageneity testing with full documentation. The optional slide feeder for Metafer extends the capability of the system, so that 80 slides can be searched unattended. The combination of the comet assay with FISH provides additional information on region specific DNA damage. Comet-FISH images can be easily captured and archived using the features of the FISH scanning software MetaCyte*.
* CometScan requires Metafer MetaCyte.
