engleski

Application of fluorescence in situ hybridization (FISH) in the diagnosis of congenital abnormalities

Constitutional chromosome abnormalities occur with an incidence of 1.8/1000 live births, and they are often associated with malformations, developmental delay, poor physical growth and mental retardation. Genomic imbalance may involve whole chromosome, chromosomal segment or subtle submicroscopic region. Precise identification of chromosomal rearrangement is very important in determining diagnosis, prognosis and treatment of the patient. In past ten years we are aware of rapid cytogenetic development and introduction of powerful methods for precise chromosome analysis. We report the results of the study performed to evaluate the advantages and limitations of conventional cytogenetics and FISH method in a selected group of 20 patients referred for suspected chromosomal aberrations. Routine chromosome analysis was performed on slides obtained by peripheral blood cultures. FISH analyisis of chromosomal rearrangement require sometimes multiple hybiridizations and use of multiple probes. In present study commercial whole-chromosome painting, centromeric, subtelomeric or locus-specific probes were used. This study demonstrates a number of advantages of FISH method over conventional cytogenetics; 1. the major advantage of FISH over traditional karyotyping is the possibility to investigate genomic imbalance in dividing and nondividing cellls. 2. FISH is very useful in the detection of cytogenetically invisible microdeletions such as 22q11 in DiGeorge syndrome. FISH using metaphase and interphase cells may unequivocally diagnose this and other microdeletion syndromes. 3. combination of metaphase analysis and interphase FISH may be an important tool in the detection of chromosomal mosaics. 4. FISH is powerful method in evaluating the chromosomes involved in translocations, and sometimes may give useful information regarding chromosome break points. FISH method however, presents some limitations: 1. in FISH experiments the information from single hybridisation is limited to 2-3 chromosome targets, while traditional cytogenetics is able to identify every chromosome ina metaphase spread. 2. FISH application usually requires some prior knowledge of chromosomal aberrations or phenotype that strongly suggests specific microdeletion syndrome in order to select the appropirate probe. 3. FISH cannot detect intrachromosomal rearrangement like inversions or chromosomal segment involved in duplications. It is necesarry to point out that FISH cannot replace the traditional karyotyping, but serve as a very useful adjunct to routine chromosome analysis.

chromosomal aberrations; microdeletions; telomere; fluorescencent in situ hybridisation

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