Assuming you are culturing appropriately and passaging the cells as necessary, FISH would be possible on amniotic cells cultured for 20 days.
For more than 30 years, cytogenetic diagnosis from amniotic cells extracted during amniocentesis has been the procedure most widely used around the world to rule out fetal chromosomal abnormalities. Methodologically, however, this procedure relies upon setting up cell cultures, so that the few embryonal/fetal cells scaled off from the amniotic specimen can be reactivated for multiplication and to prepare the fetal chromosomes from these cells. The chromosomes are only visible under the microscope during the metaphase of the cell cycle. For most of the time, however, the cells are in the interphase of the cell cycle, during which period the chromosomes cannot be detected by conventional cytogenetic methods, since they are only prevalent during this phase in decondensed form. Each individual chromosome can also only be stained differentially during the metaphase by special banding techniques. The cell culture takes about 10–12 days. This period of time is extremely irksome to many pregnant women and their attending gynecologists, particularly in cases presenting a high risk of fetal chromosomal abnormality. Given the huge advances in molecular genetics, it has been possible for more then ten years now to make direct use of uncultured fetal cells (as a rule: amniocytes) for analysis in the interphase of the cell cycle—in other words, without any prior cultivation of cells. In this procedure, fluorescent, chromosome-specific DNA probes (Abbott Molecular/Vysis, Wiesbaden, Germany) are hybridized (fluorescence in situ hybridization, FISH) with native amniocytes and analyzed under the microscope. Normally this is a routine matter when there are grounds to suspect numeric aneuploidies with chromosomes 13, 18, 21, X, Y; for example, during the late stages of pregnancy, with certain findings after ultrasonic examination, when the mother is of a more advanced age, in cases of mental indications, and for specific family histories.
Thomas Liehr
Editor
Fluorescence In Situ
Hybridization (FISH) –
Application Guide
Editor
Dr. Thomas Liehr
Institut für Humangenetik und Anthropologie
Kollegiengasse 10
07743 Jena
Germany
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