FISH Techniques, FISH Probes and Their Applications in Medicine and Biology - An Overview
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In preimplantation genetic diagnosis (PGD) interphase FISH (Delhanty et al. 1993, Verlinsky et al. 1996) also allows for a rapid screening
of the most common chromosomal aneuploidies. This offers the opportunity to avoid the implantation of fertilized eggs carrying a numerical
chromosome aberration. Investigation of aneuploidies for other chromosomes is also possible and interphase FISH has been employed for identifying chromosome balance in early embryos from patients with reciprocal translocations (Pierce et al. 1998).
In oncology the possibility of using interphase-FISH with translocation-specific probes is of particular interest when the quality of metaphases are poor or if non-viable fiXed tumors are used. Furthermore, analysis for specific chromosomal abnormalities in tissues directly without
the need for cell propagation may give important information on heterogeneity. The types of chromosome aberrations that can be diagnosed by
interphase-FISH are deletions of tumor-suppressor genes e.g. retinoblastoma gene (Chang et al. 1999), amplification of oncogenes e.g. N-myc in
neuroblastoma (Hachitanda et al. 1999) and specific types of translocations e.g. Philadelphia chromosome (Yanagi et al. 1999) as well as numerical aberrations (Worsham et al. 1999).
Many malignancies are also characterized by the presence of many cell
subpopulations with different genome rearrangements. In these situations
molecular cytogenetic analysis is superior to molecular techniques. Standard molecular techniques such as for example PCR would give data that
represents the average of aberrations over the whole cell population. When
chromosome analysis is undertaken, it is evident that inspection and characterization of the genome of single cells takes place, and thus data on cell
diversity is obtained as well. With regard to single cell analysis, interphaseFISH sometimes offers advantages over conventional banding and metaphase FISH. This is due to the fact that these metaphases are obtained by
initial cell culturing. When analyzing mixed cell populations there is no
guarantee that all subpopulations proliferate to a similar extent during cell
culturing. This means that there is a risk ofgettingverydistorted estimates on
the distribution of cell subpopulations after culturing. Interphase-FISH
offers a simple solution to this problem, since no cellular propagation
is involved, therefore allowing for true estimates ofcell fractions. Ofcourse,
interphase-FISH has severe problems in terms ofmore detailed screening of
the whole genome, but ifdetection ofspecific regions is needed, this method
offers many advantages, including possibilities for analyzing archive materials or solid tumors that have very low mitotic indexes.
It has recently been found that the subtelomeric regions have the highest number of genes per unit chromosome in the entire genome. Cryptic
31
In preimplantation genetic diagnosis (PGD) interphase FISH (Delhanty et al. 1993, Verlinsky et al. 1996) also allows for a rapid screening
of the most common chromosomal aneuploidies. This offers the opportunity to avoid the implantation of fertilized eggs carrying a numerical
chromosome aberration. Investigation of aneuploidies for other chromosomes is also possible and interphase FISH has been employed for identifying chromosome balance in early embryos from patients with reciprocal translocations (Pierce et al. 1998).
In oncology the possibility of using interphase-FISH with translocation-specific probes is of particular interest when the quality of metaphases are poor or if non-viable fiXed tumors are used. Furthermore, analysis for specific chromosomal abnormalities in tissues directly without
the need for cell propagation may give important information on heterogeneity. The types of chromosome aberrations that can be diagnosed by
interphase-FISH are deletions of tumor-suppressor genes e.g. retinoblastoma gene (Chang et al. 1999), amplification of oncogenes e.g. N-myc in
neuroblastoma (Hachitanda et al. 1999) and specific types of translocations e.g. Philadelphia chromosome (Yanagi et al. 1999) as well as numerical aberrations (Worsham et al. 1999).
Many malignancies are also characterized by the presence of many cell
subpopulations with different genome rearrangements. In these situations
molecular cytogenetic analysis is superior to molecular techniques. Standard molecular techniques such as for example PCR would give data that
represents the average of aberrations over the whole cell population. When
chromosome analysis is undertaken, it is evident that inspection and characterization of the genome of single cells takes place, and thus data on cell
diversity is obtained as well. With regard to single cell analysis, interphaseFISH sometimes offers advantages over conventional banding and metaphase FISH. This is due to the fact that these metaphases are obtained by
initial cell culturing. When analyzing mixed cell populations there is no
guarantee that all subpopulations proliferate to a similar extent during cell
culturing. This means that there is a risk ofgettingverydistorted estimates on
the distribution of cell subpopulations after culturing. Interphase-FISH
offers a simple solution to this problem, since no cellular propagation
is involved, therefore allowing for true estimates ofcell fractions. Ofcourse,
interphase-FISH has severe problems in terms ofmore detailed screening of
the whole genome, but ifdetection ofspecific regions is needed, this method
offers many advantages, including possibilities for analyzing archive materials or solid tumors that have very low mitotic indexes.
It has recently been found that the subtelomeric regions have the highest number of genes per unit chromosome in the entire genome. Cryptic