CGH | CGH

Key Words: fluorophore, fluorescence, cytogenetics, fluorescence filters, FISH, mFISH, microdissection

Definition:CGH is a cytogenetic technique used to detect DNA gains and losses across species or in diseased cells (especially cancer cells) compared with healthy cells

Technology:

Comparative genomic hybridization (CGH) is an analytical method based on FISH and digital fluorescence ratio measurements. It allows the identification and mapping of chromosome imbalances in one specimen relative to another, for example, a cancer cell compared with a normal cell. CGH can be carried out on microarrays and makes the analysis of entire genomes possible. Two genomic DNA samples are hybridised simultaneously in situ to normal human cytogenetic metaphase preparations and detected with different fluorophores. The ratio of the intensities of the two fluorophores, detected with fluorescence microscopy emplying appropriate filters, is a measure of the copy number ratio between the two DNA samples.

Technology applications:

CGH can be used for DNA analysis to compare DNA from a wide variety of sources to detect DNA imbalances. Its greatest application, however, is in the identification of consistent DNA gains and losses reponsible for disease. It can be used in prenatal diagnosis, in the diagnsotic evaluation of cancerous tissues, and in obtaining a better understanding of species differences in disease, especially in disease models for research and drug discovery. It can be used with fresh or fixed samples, allowing restrospective analysis of archived samples.

Microscope configuration:

CGH can be carried out on any Nikon research-level upright microscope or inverted epi-fluorescence microscope (typically on upright) with appropriate light filters. CGH requires high-resolution optics, high-signal-to-noise ratios, and high sensitivity. Deconvolution processing helps to reduce out-of-focus light, which restricts contrast and detection limits. Data analysis software, such as Genikon, automates image analysis and facilitates results reporting and data archiving.

System solution:

The Eclipse 90i is ideally suited to the capture of low light fluorescence data and enables automated image capture. A variety of commercially available cytogenetic data analysis software packages are available to facilitate image interpretation.

More information:

www.microscopyu.com/articles/fluorescence/insitu/brennerinsitu