Abstract
BackgroundChromosomal dissection provides a direct advance for isolating DNA from cytogenetically recognizable region to generate genetic probes for fluorescence in situ hybridization, a technique that became very common in cyto and molecular genetics research and diagnostics. Several reports describing microdissection methods (glass needle or a laser beam) to obtain specific probes from metaphase chromosomes are available. Several limitations are imposed by the traditional methods of dissection as the need for a large number of chromosomes for the production of a probe. In addition, the conventional methods are not suitable for single chromosome analysis, because of the relatively big size of the microneedles. Consequently new dissection techniques are essential for advanced research on chromosomes at the nanoscale level.ResultsWe report the use of Atomic Force Microscope (AFM) as a tool for nanomanipulation of single chromosomes to generate individual cell specific genetic probes. Besides new methods towards a better nanodissection, this work is focused on the combination of molecular and nanomanipulation techniques which enable both nanodissection and amplification of chromosomal and chromatidic DNA. Cross-sectional analysis of the dissected chromosomes reveals 20 nm and 40 nm deep cuts. Isolated single chromosomal regions can be directly amplified and labeled by the Degenerate Oligonucleotide-Primed Polymerase Chain Reaction (DOP-PCR) and subsequently hybridized to chromosomes and interphasic nuclei.ConclusionsAtomic force microscope can be easily used to visualize and to manipulate biological material with high resolution and accuracy. The fluorescence in situ hybridization (FISH) performed with the DOP-PCR products as test probes has been tested succesfully in avian microchromosomes and interphasic nuclei. Chromosome nanolithography, with a resolution beyond the resolution limit of light microscopy, could be useful to the construction of chromosome band libraries and to the molecular cytogenetic mapping related to the investigation of genetic diseases.
Highlights
Chromosomal dissection provides a direct advance for isolating DNA from cytogenetically recognizable region to generate genetic probes for fluorescence in situ hybridization, a technique that became very common in cyto and molecular genetics research and diagnostics
We introduce nanolithography on chromosomes surface where contiguous line patterns can be generated by a softwarecontrolled pattern generator built in the Atomic Force Microscope (AFM) controller
Our experiments have clearly shown that dissected DNA can subsequently be used as material for PCR amplification and labeling to generate single-cell genetic probe for fluorescence in situ hybridization (FISH) analysis
Summary
Chromosomal dissection provides a direct advance for isolating DNA from cytogenetically recognizable region to generate genetic probes for fluorescence in situ hybridization, a technique that became very common in cyto and molecular genetics research and diagnostics. By approaching the cantilever to the sample, the interaction forces can be measured and controlled; upon scanning the surface it will be possible to record the topography of the sample. This features allow the AFM to work on unstained and uncoated chromosomes [7]. The AFM imaging reveals that the chromosomes are not uniform in structure but have, along their length, ridges and grooves that may be related to the G-positive and G-negative bands respectively [8,9] In this way it is possible to recognize and manipulate chromosomal regions without staining and coating
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