A simple method for enhancing hybridization efficiency in chromosome and array comparative genomic hybridization

The accuracy of comparative genomic hybridization (CGH) analysis is affected by hybridization efficiency. We describe here a simple method for enhancing hybridization efficiency. The hybridization procedure is essentially the same as that of conventional methods. Hybridization solution containing denatured DNA probe mixture was applied to a metaphase chromosome slide or DNA chip slide and covered with a coverslip. In the new method, however, the slide was inverted by turning the coverslip downward prior to hybridization. We termed this method the inverted slide method. To estimate the efficiency of the new method, metaphase chromosome slides and DNA chip slides were treated by both the conventional and inverted slide methods and incubated in a moist chamber at 37°C for 12, 24, 48, and 72 h. Hybridization signals were approximately 1.5 to 2 times brighter on the slides using the inverted slide method than those using the conventional method after 48 and 72 h of incubation. Furthermore, topographical differences in fluorescence intensity were smaller in slides using the inverted-slide method than in those prepared by the conventional method. The inverted slide method is methodologically very simple and improves the resolution of CGH.