Considerations on the scoring of telomere aberrations in vertebrate cells detected by telomere or telomere plus centromere PNA-FISH

Given that telomeres play a fundamental role in maintaining genomic stability, the study of the chromosomal aberrations involving telomeric sequences is a topic of considerable research interest. In recent years, the scoring of these types of aberrations has been used in vertebrate cells, particularly human cells, to evaluate the effects of genotoxic agents on telomeres and the involvement of telomeric sequences on chromosomal aberrations. Currently, chromosomal aberrations involving telomeric sequences are evaluated in peripheral blood lymphocytes or immortalized cell lines, using telomere or telomere plus centromere fluorescence in situ hybridization (FISH) with Peptide Nucleic Acid (PNA) probes (PNA-FISH). The telomere PNA probe is more efficient in the detection of telomeric sequences than conventional FISH with a telomere DNA probe. In addition, the intensity of the telomeric PNA-FISH probe signal is directly correlated with the number of telomeric repeats. Therefore, use of this type of probe can identify chromosomal aberrations involving telomeres as well as determine the telomere length of the sample. There are several mistakes and inconsistencies in the literature regarding the identification of telomere aberrations, which prevent accurate scoring and data comparison between different publications concerning these types of aberrations. The aim of this review is to clarify these issues, and provide proper terminology and criteria for the identification, scoring, and analysis of telomere aberrations.