The Chromosomal Distribution of Microsatellite Repeats in the Genome of the Wolf Fish <i>Hoplias malabaricus</i>, Focusing on the Sex Chromosomes

Abstract

Distribution of 12 mono-, di- and tri-nucleotide microsatellites on the chromosomes of 2 karyomorphs with 2 distinct sex chromosome systems (a simple XX/XY – karyomorph B and a multiple X₁X₁X₂X₂/X₁X₂Y – karyomorph D) in Hoplias malabaricus, commonly referred to as wolf fish, was studied using their physical mapping with fluorescence in situ hybridization (FISH). The distribution patterns of different microsatellites along the chromosomes varied considerably. Strong hybridization signals were observed at subtelomeric and heterochromatic regions of several autosomes, with a different accumulation on the sex chromosomes. A massive accumulation was found in the heterochromatic region of the X chromosome of karyomorph B, whereas microsatellites were gathered at centromeres of both X chromosomes as well as in corresponding regions of the neo-Y chromosome in karyomorph D. Our findings are likely in agreement with models that predict the accumulation of repetitive DNA sequences in regions with very low recombination. This process is however in contrast with what was observed in multiple systems, where such a reduction might be facilitated by the chromosomal rearrangements that are directly associated with the origin of these systems.

Hypermethylated Chromosome Regions in Nine Fish Species with Heteromorphic Sex Chromosomes

“…The largest accumulation of these repeats was found in the long arms of the sex chromosomes which are notably heterochromatic [Cioffi et al, , 2011Poltronieri et al, 2014;Yano et al, 2014]. The accumulation of repetitive DNA sequences in the sex chromosomes of these fishes is highly variable, even among closely related species.…”

“…In the present study, the amounts and positions of 5-MeC-rich chromosome regions were detected in 9 Brazilian Characiformes fish species belonging to the genera Leporinus , Triportheus and Hoplias using indirect immunofluorescence and a highly specific monoclonal anti-5-MeC antibody. Leporinus obtusidens and all Triportheus species examined possess well-differentiated ZW sex chromosomes [Galetti and Foresti, 1986;Artoni et al, 2001], whereas Hoplias malabaricus (karyomorph B) has highly differentiated XY sex chromosomes [Cioffi et al, 2011].…”

Comparative Chromosome Mapping of U2 snRNA and 5S rRNA Genes in <b><i>Gymnotus</i></b> Species (Gymnotiformes, Gymnotidae): Evolutionary Dynamics and Sex Chromosome Linkage in <b><i>G</i></b>. <b><i>pantanal</i></b>

“…cluding transposable elements, histone genes, microsatellite repeats and/or U1/U2 small nuclear RNA (snRNA) genes [Cioffi et al, 2010;Úbeda-Manzanaro et al, 2010;Ferreira et al, 2011;Hashimoto et al, 2011;Cabral-deMello et al, 2012]. The U snDNA is a multigene family of non-coding RNAs that compounds the spliceosome machinery and may be subdivided into 5 types, including U1, U2, U4, U5, and U6 [Valadkhan, 2005].…”

Independent Sex Chromosome Evolution in Lower Vertebrates: A Molecular Cytogenetic Overview in the Erythrinidae Fish Family

“…In karyomorph B, which has an XY system, the accumulation of repetitive DNA sequences played an important role in the differentiation of the sex chromosomes. In fact, a large accumulation of different classes of microsatellites occurred on the highly heterochromatic long arm of the X chromosome, in comparison to the distribution of these DNA repeats in other chromosomes of the karyotype [Cioffi et al, 2011]. In karyomorph C, molecular cytogenetic markers enabled the identification of a nascent XY sex system, where the X chromosome can be distinguished by the amplification of a small GC-positive heterochromatic region in association with an rDNA cluster .…”