Global heterochromatic colocalization of transposable elements with minisatellites in the compact genome of the pufferfish Tetraodon nigroviridis

• Published in: Gene Vol. 336; no. 2; pp. 175 - 183
• Main Authors: Fischer, Cécile, Bouneau, Laurence, Coutanceau, Jean-Pierre, Weissenbach, Jean, Volff, Jean-Nicolas, Ozouf-Costaz, Catherine
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 21-07-2004
• Subjects: Amino Acid Sequence; Animals; Base Sequence; DNA - chemistry; DNA - genetics; DNA Transposable Elements - genetics; Drosophila melanogaster; Fluorescent in situ hybridization; Genome; Heterochromatin; Heterochromatin - genetics; In Situ Hybridization, Fluorescence; Minisatellite Repeats - genetics; Molecular Sequence Data; Repeated DNA; Retroelements - genetics; Retrotransposon; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Takifugu rubripes; Tetraodon nigroviridis; Tetraodontiformes - genetics; Transposases - genetics; Transposon; Repeated DNA; Retrotransposon; Heterochromatin; Transposon; ms; FISH; Fluorescent in situ hybridization; DAPI; TIR
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2004.04.014

Because of its unusual high degree of compaction and paucity of repetitive sequences, the genome of the smooth pufferfish
Tetraodon nigroviridis is the subject of a well-advanced sequencing project. An astonishing diversity of transposable elements not found in the human and the mouse has been observed in the genome of
T. nigroviridis. Due to the difficulty of assembling repeat-rich regions, the whole genome shotgun sequencing approach will probably fail to reveal the general organisation of this compact vertebrate genome. Therefore, in order to gain new insights into the global distribution pattern of repeated DNA in the genome of
T. nigroviridis, we have reconstructed partial/complete repetitive sequences from data generated by the genome project and performed double-colour fluorescent in situ hybridization (FISH) analysis for representatives of three major categories of repeated sequences including two minisatellites (
ms100 and
ms104), two DNA transposons (
Tol2 and
Buffy1) and two non-long terminal repeat (LTR) retrotransposons (
Rex3 and
Babar). We show that DNA transposons and retroelements very frequently colocalize with minisatellites and mostly accumulate within heterochromatic regions. These results, which have not been reported so far for the fugu
Takifugu rubripes, show that repeated elements are generally excluded from gene-rich regions in
T. nigroviridis and underline the extreme degree of compartmentalization of this compact genome. The genome organization of the pufferfish is clearly different from that observed in humans, where repeated sequences make up an important fraction of euchromatic DNA, and is more similar to that observed in the fruit fly
Drosophila melanogaster.