How Does aCGH Work?
The process begins with the extraction of DNA from both the test and reference samples. These DNA samples are then labeled with different fluorescent dyes. The labeled DNA is hybridized to a microarray containing thousands of DNA probes corresponding to different genomic regions. Following hybridization, the microarray is scanned, and the fluorescence intensity is measured. By comparing the fluorescence intensities, researchers can determine relative DNA copy number changes in the test sample compared to the reference.
Applications in Histology
In
histology, aCGH is particularly useful for the analysis of tissue samples to identify genomic aberrations associated with various diseases, including cancer. By pinpointing specific genetic changes in tissue samples, aCGH can aid in the
diagnosis and prognosis of diseases. For instance, in cancer histology, it helps identify genetic
mutations and deletions that drive tumorigenesis, informing targeted therapy decisions.
Advantages of aCGH
High-resolution detection of genomic alterations.
Ability to detect both gains and losses of DNA segments.
Comprehensive genome-wide analysis.
Non-reliance on prior knowledge of specific genomic regions.
Useful in identifying
submicroscopic alterations that may not be detected by other techniques.
Limitations of aCGH
Despite its advantages, aCGH has some limitations. It cannot detect balanced chromosomal rearrangements, such as inversions or translocations, as these do not result in copy number changes. Additionally, the resolution of aCGH is dependent on the density of probes on the array, which may limit the detection of very small genomic changes. Furthermore, aCGH can generate a large amount of data, requiring sophisticated bioinformatics tools for analysis and interpretation. Interpretation of Results
Interpreting aCGH results involves analyzing the fluorescence intensity ratios of test and reference samples across the genome. Regions with increased fluorescence intensity in the test sample indicate
DNA copy number gains, while decreased intensity indicates losses. These findings are then correlated with known genomic regions and associated diseases. For instance, gains in certain oncogenes or losses in tumor suppressor genes can provide insights into the genetic basis of a tumor.
Future Directions
The integration of aCGH with other genomic technologies, such as
next-generation sequencing (NGS), promises to enhance the resolution and accuracy of genomic analysis. Additionally, advancements in microarray technology and bioinformatics tools are expected to improve the sensitivity and specificity of aCGH, making it an even more powerful tool in histological research and clinical diagnostics.
Conclusion
Array Comparative Genomic Hybridization (aCGH) is a valuable technique in the field of histology, offering high-resolution detection of genomic alterations. Its ability to identify DNA copy number changes across the entire genome makes it indispensable for the diagnosis and study of various diseases, particularly cancer. Despite its limitations, ongoing advancements in technology and bioinformatics are poised to further enhance the utility of aCGH in histological analysis.
