Telomere aggregates in amniocytes with karyotype of balanced chromosomal rearrangements

Telomeres are TTAGGG repetitions at the ends of chromosomes. Functioning telomeres are essential for normal segregation and maintenance of chromosomes during mitotic and meiotic divisions. Dysfunctional telomeres support the survival of aneuploid cells, a characteristic of many human malignancies. In contrast to the non-overlapping nature of telomeres in normal nuclei, telomeres of tumor nuclei tend to form aggregates. In this study, our objective was to evaluate the number of telomere aggregates (TAs) in karyotype-balanced structural rearrangements. This is an additional parameter of genetic instability, which might suggest a possible increased risk for diseases related to genomic instability, such as cancer. Twenty-six amniotic fluid cell cultures were established following genetic amniocentesis. Telomere FISH protocol was applied to the samples. Telomere aggregates were counted using a 2D microscope. The results were statistically tested by analysis of variance (ANOVA) and Kruskal-Wallis tests. More telomere aggregates in the structural balanced rearrangements were found in both study groups (balanced translocations and inversions) compared to the control group (P < 0.05). The persistence of TAs in cells is probably related to Breakage-Bridge-Fusion (BBF) cycles, a mechanism of TAs described by Muller and McClintock, resulting in end-to-end fusion that contributes to the onset of genomic instability. BBF cycles contribute to deletions, gene amplification, non-reciprocal translocations, and overall genetic changes associated with tumor genesis. According to our studies, the individuals who are carriers of balanced structural chromosomal rearrangements show some of the genetic instability parameters that appear in other circumstances, such as premalignant and malignant conditions.