Micro-CGH: Microdissection-Based Comparative Genomic Hybridization

Comparative genomic hybridization (CGH) is a well-established technique in the field of molecular cytogenetics for performing the comprehensive analysis of chromosomal imbalances of entire human genomes. Genomic DNA from a tested specimen (test DNA) and a normal one (reference DNA) are differentially labeled and simultaneously hybridized to normal metaphase spreads. The ratio of fluorescence intensity along each normal chromosome is analyzed, allowing the detection of regions that are over- or underrepresented in the tested specimen. In this chapter, we describe the technique of CGH itself and a variant of it. The so-called micro-CGH (microdissection-based comparative genomic hybridization) technique allows molecular cytogenetics investigations of harvested and cytogenetically fixed (bone marrow) interphase nuclei. The latter must be microdissected from the surface of a coverslip, and the small amount of DNA present is amplified by a universal PCR using degenerate oligonucleotide primers (DOP-PCR). The PCR products are labeled and thus transformed into FISH probes. Micro-CGH has already been used in leukemia cytogenetics, as well as in clinical genetics.