Posttraumatic regeneration involves differential expression of long terminal repeat (LTR) retrotransposons.
BACKGROUND
Retrotransposons are mobile genetic elements that constitute a sizable proportion of eukaryote genomes. Although retroelements are known to play significant roles in embryogenesis, stress reactions, and disease progression, they have never been studied in the context of animal regeneration.


RESULTS
In this study, high-throughput transcriptome analysis revealed unexpectedly large-scale changes in transcriptional activity of retrotransposons in regenerating radial organs of the sea cucumber Holothuria glaberrima. In particular, we identified 36 long terminal repeat (LTR) retroelements, of which 20 showed significant changes in their expression during regeneration (11 up-regulated, 8 down-regulated, and one was initially up-regulated, but later down-regulated). We then studied in detail the most significantly up-regulated element, Gypsy-1_Hg. This transposon showed a drastic (>50-fold) increase in expression in regeneration and started to return to the normal levels only after the anatomical organization of the injured tissues was restored. All cells expressing Gypsy-1_Hg were located in the vicinity of the wound and included glia and neurons of the radial nerve. The retrotransposon-expressing cells survived programmed cell death and contributed to regeneration.


CONCLUSIONS
Our findings demonstrate considerable changes in transcriptional activity of retrotransposons (both over-expression and down-regulation) associated with posttraumatic regeneration in an echinoderm.
Department of Biology, University of Puerto Rico, San Juan, Puerto Rico. mashanovvlad@googlemail.com
Vladimir S
VS
Mashanov
Olga R
OR
Zueva
José E
JE
García-Arrarás
D000818:Animals; D005121:Extremities / Q000502:physiology; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D012038:Regeneration / Q000235:genetics / Q000502:physiology*; D018626:Retroelements / Q000235:genetics*; D012616:Sea Cucumbers / Q000502:physiology*; D020079:Terminal Repeat Sequences / Q000235:genetics*
D018626:Retroelements