Journal
ZEBRAFISH
Volume 14, Issue 2, Pages 146-154Publisher
MARY ANN LIEBERT, INC
DOI: 10.1089/zeb.2016.1351
Keywords
multigene families; sex chromosomes; repetitive DNAs
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Funding
- CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico) [306896/2014-1]
- FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo) [2014/22532-7]
- CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior) [BEX 11744/13-8]
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Multigene families correspond to a group of genes tandemly repeated, showing enormous diversity in both number of units and genomic organization. In fishes, unlike rDNAs that have been well explored in cytogenetic studies, U2 small nuclear RNA (snRNA) genes are poorly investigated concerning their chromosomal localization. All Triportheus species (Characiformes, Triportheidae) studied so far carry a ZZ/ZW sex chromosomes system, where the W chromosome contains a huge 18S rDNA cistron. In some species the syntenic organization of rDNAs on autosomes was also verified. To explore this particular organization, we performed three-color-fluorescence in situ hybridization using 5S, 18S rDNA, and U2 snRNA genes as probes in eight Triportheus species. This work represents the first one analyzing the chromosomal distribution of U2 snRNA genes in genomes of Triportheidae. The variability in number of rDNA clusters, and the divergent syntenies for these three multigene families, put in evidence their evolutionary dynamism, revealing a much more complex organization of these genes than previously supposed for closely related species. Our study also provides additional data on the accumulation of repetitive sequences in the sex-specific chromosome. Besides, the chromosomal organization of U2 snDNAs among fish species is also reviewed.
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