engleski

Fluorescence in situ hybridization: a Gold Standard in Identification of Small Supernumerary Marker Chromosome in Prenatal Diagnostics

Small supernumerary marker chromosome (sSMC) is a structurally abnormal chromosome. It is an additional chromosome mainly detected, but rarely identifiable by conventional cytogenetic analysis. To identify the origin and composition of a specific sSMC, the application of a molecular cytogenetic method is essential. Despite the recent escalation of high-throughput methods, fluorescence in situ hybridization (FISH), as a powerful and sensitive technique with simple and inexpensive laboratory procedure, is still the method of choice in the characterization of sSMC structure. The aim of this study was to analyze the sSMC collected since 2009 in our Laboratory and to direct attention to the value of the FISH method in determining the origin of sSMC in prenatal diagnosis. A combination of conventional karyotyping and FISH were performed on cultured amniocytes as an effective utilization strategy in sSMC detection. The overall frequency of sSMCs was 0.24% (6/2456). Indications for prenatal diagnosis in those six cases were maternal age (2/6), first- trimester combined screening test (2/6) and ultrasound finding (2/6). Mosaic karyotypes were present in 66.67% (4/6) cases. FISH analyses revealed that the majority of sSMCs (50.00%) originate from chromosome 15. They were found to be dicentric (15), isochromosomes (12, 18) and centric minute (19). De novo origin of sSMC was detected in most of the cases (83.33%), except one dicentric 15, which was inherited from the mother. Gained experience in the field of molecular cytogenetics allows us to conclude that FISH remains to be a gold standard in the identification of sSMCs in prenatal diagnostics.

FISH, marker chromosome, prenatal diagnostics

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