Chromosomal aberrations involving telomeres and interstitial telomeric sequences

Abstract

Telomeres are specialised nucleoproteic complexes localised at the physical ends of linear eukaryotic chromosomes that maintain their stability and integrity. In vertebrate chromosomes, the DNA component of telomeres is constituted by (TTAGGG)n repeats, which can be localised at the terminal regions of chromosomes (true telomeres) or at intrachromosomal sites (interstitial telomeric sequences or ITSs, located at the centromeric region or between the centromere and the telomere). In the past two decades, the use of molecular cytogenetic techniques has led to a new spectrum of spontaneous and clastogen-induced chromosomal aberrations being identified, involving telomeres and ITSs. Some aberrations involve the chromosome ends and, indirectly, the telomeric repeats located at the terminal regions of chromosomes (true telomeres). A second type of aberrations directly involves the telomeric sequences located at the chromosome ends. Finally, there is a third class of aberrations that specifically involves the ITSs. The aims of this review are to provide a detailed description of these aberrations and to summarise the available data regarding their induction by physical and chemical mutagens.

A beginning of the end: new insights into the functional organization of telomeres

“…Large regions of repetitive telomeric repeats that can be found at internal genomic sites have been shown to correlate with fragile sites and hot spots for recombination. [35][36][37] In order to determine if only large blocks of telomeric DNA associate with recombination, we asked whether very small ITSs, for these purposes defined as 2 TTAGGG repeats separated by less than 100bp, also show a correlation with increased recombination frequency. 38 We determined that these small ITSs reveal an enriched frequency of recombination genome-wide (P < 0.04) (Fig.…”

Comparative cytogenetics of tree frogs of the Dendropsophus marmoratus (Laurenti, 1768) group: conserved karyotypes and interstitial telomeric sequences

“…Several studies support the hypothesis that, in addition to possibly representing relics of chromosomal changes, the het-ITSs may themselves induce chromosome breakage and subsequent chromosomal rearrangements (reviewed in Ruiz-Herrera et al 2008 andBolzán 2012). Similarly, experimental and associative studies have also suggested the involvement of s-ITSs with genomic instability or chromosomal hot spots of recombination (Aksenova et al 2013, Wood et al 2015.…”

The Organization of Repetitive DNA in the Genomes of Amazonian Lizard Species in the Family Teiidae

“…The mapping of repetitive sequences (TTAGGG) n in the teiid species analyzed in this study revealed conspicuous and tenuous signals in telomeric, centromeric, and interstitial regions in addition to an absence of telomeric signals in some chromosomes. This may be explained by various mechanisms that could entail small telomeric residues and could not be detected by conventional FISH, such as a reduction in the number of (TTAGGG) n repeats in the genome, telomere inactivation, and the molecular erosion process of telomeric sequences [Mandrioli et al, 1999;Nanda et al, 2002;Revaud et al, 2009;DeBaryshe and Pardue, 2011;Bolzán, 2012]. Still, these different mechanisms do not necessarily explain the total loss of telomeric sequences, only the occurrence of telomere shortening [Bolzán, 2012].…”

“…This may be explained by various mechanisms that could entail small telomeric residues and could not be detected by conventional FISH, such as a reduction in the number of (TTAGGG) n repeats in the genome, telomere inactivation, and the molecular erosion process of telomeric sequences [Mandrioli et al, 1999;Nanda et al, 2002;Revaud et al, 2009;DeBaryshe and Pardue, 2011;Bolzán, 2012]. Still, these different mechanisms do not necessarily explain the total loss of telomeric sequences, only the occurrence of telomere shortening [Bolzán, 2012]. This has also been described for a bat species of the family Molossidae, where the absence of chromosome end signals was identified in Eumops auripendulus [Faria et al, 2009].…”