Handling Editor: Benoit Bruneau
ABSTRACT
Heart regeneration in regeneration-competent organisms can be accomplished through the remodeling of gene expression in response to cardiac injury. This dynamic transcriptional response relies on the activities of tissue regeneration enhancer elements (TREEs); however, the mechanisms underlying TREEs are poorly understood. We dissected a cardiac regeneration enhancer in zebrafish to elucidate the mechanisms governing spatiotemporal gene expression during heart regeneration. Cardiac lepb regeneration enhancer (cLEN) exhibits dynamic, regeneration-dependent activity in the heart. We found that multiple injury-activated regulatory elements are distributed throughout the enhancer region. This analysis also revealed that cardiac regeneration enhancers are not only activated by injury, but surprisingly, they are also actively repressed in the absence of injury. Our data identified a short (22 bp) DNA element containing a key repressive element. Comparative analysis across Danio species indicated that the repressive element is conserved in closely related species. The repression mechanism is not operational during embryogenesis and emerges when the heart begins to mature. Incorporating both activation and repression components into the mechanism of tissue regeneration constitutes a new paradigm that might be extrapolated to other regeneration scenarios.
Footnotes
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: I.J.B., K.S., F.J.P., J.K.; Methodology: I.J.B., K.S., D.O.-M., A.K., J.K.; Validation: I.J.B., K.S., D.O.-M.; Formal analysis: I.J.B., K.S.; Ivestigation: I.J.B., K.S., D.O.-M., A.K.,J.K.; Resources: I.J.B., K.S., N.L., T.J.C., F.J.P., J.K.; Writing - original draft: I.J.B., J.K.; Writing - review & editing: I.J.B., K.S., D.O.-M., J.K.; Visualization: I.J.B., K.S., D.O.-M., J.K.; Supervision: J.K.; Project administration: I.J.B., K.S., J.K.; Funding acquisition: F.J.P., J.K.
Funding
This work was supported by the National Institutes of Health, under a Ruth L. Kirschstein National Research Service Award from the National Heart, Lung and Blood Institute to the University of Wisconsin-Madison Cardiovascular Research Center (T32 HL 007936 to I.J.B.) and from the National Institute Of General Medical Sciences to the University of Wisconsin-Madison Genetics Graduate Training Program (T32 GM 007133 to T.J.C. and D.O.-M.), by a U.S. Department of Agriculture Hatch grant and the University of Wisconsin-Madison UW2020 Round 6 award to F.J.P., by the National Institutes of Health (R35 GM 137878), by University of Wisconsin-Madison start-up funds (AAC8355, AAC8979, AAC6429 and AAG9756), by an American Heart Association grant (AHA16SDG30020001 to J.K.), and by a University of Wisconsin Carbone Cancer Center Support Grant (P30 CA014520 to J.K.). Deposited in PMC for release after 12 months.
Supplementary information
Supplementary information available online at https://dev.biologists.org/lookup/doi/10.1242/dev.194019.supplemental
- Received June 15, 2020.
- Accepted November 13, 2020.
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