DNA breakpoints and chromosomal rearrangements in Loricariidae fishes (Teleostei, Siluriformes): A cytogenetic and molecular approach

Abstract

Fishes of the Loricariidae (Teleostei, Siluriformes) present a wide morphological variation, as well as a wide karyotype variability, both in diploid number (2n) and structural chromosomal diversity, due to chromosomal rearrangements occurred throughout the evolutionary history of its species. The occurrence of chromosomal rearrangements is closely associated with DNA breaks in sites enriched in repetitive sequences. Telomeres are repetitive DNA sequences located in the terminal region of chromosomes, whose function is to maintain their stability and integrity. Such sequences may eventually be found in other chromosomal regions, the so-called interstitial telomeric sites (ITSs). It is proposed that ITSs have arisen as a result of chromosomal rearrangements in the evolution of genomes and that their occurrence may cause chromosomal instability. In addition, there is also evidence of the involvement of ribosomal DNAs in chromosomal break-points and rearrangements. The reuse of the same DNA sequence at the origin of the chromosomal rearrangements in genomes of close lineages is the key feature of the evolutionary model of double-strand breakpoints. This predisposition to instability and breaks of certain genomic regions is described as "evolutionary breakpoints", which are considered hotspots for chromosomal rearrangements. However, studies of repetitive DNA families in Neotropical fishes, correlating these sequences to chromosomal rearrangement events, are still very scarce. Therefore, the objective of this work is to characterize repetitive DNAs in fishes of the Loricariidae family, focusing on chromosomal breakpoints responsible for their karyotype diversity, aiming to understand the genomic evolution of this specious group of Neotropical ichthyofauna (AU)