Dynamic microRNA-101a and Fosab expression controls zebrafish heart regeneration

Abstract

Cardiovascular disease is the leading cause of morbidity and mortality in the Western world owing to the limited regenerative capacity of the mammalian cardiovascular system. In lieu of new muscle synthesis, the human heart replaces necrotic tissue with deposition of a noncontractile scar. By contrast, the adult zebrafish is endowed with a remarkable regenerative capacity, capable of de novo cardiomyocyte (CM) creation and scar tissue removal when challenged with an acute injury. In these studies, we examined the contributions of the dynamically regulated microRNA miR-101a during adult zebrafish heart regeneration. We demonstrate that miR-101a expression is rapidly depleted within 3 days postamputation (dpa) but is highly upregulated by 7-14 dpa, before returning to uninjured levels at the completion of the regenerative process. Employing heat-inducible transgenic strains and antisense oligonucleotides, we demonstrate that decreases in miR-101a levels at the onset of cardiac injury enhanced CM proliferation. Interestingly, prolonged suppression of miR-101a activity stimulates new muscle synthesis but with defects in scar tissue clearance. Upregulation of miR-101a expression between 7 and 14 dpa is essential to stimulate removal of the scar. Through a series of studies, we identified the proto-oncogene fosab (cfos) as a potent miR-101a target gene, stimulator of CM proliferation, and inhibitor of scar tissue removal. Importantly, combinatorial depletion of fosab and miR-101a activity rescued defects in scar tissue clearance mediated by miR-101a inhibition alone. In summation, our studies indicate that the precise temporal modulation of the miR-101a/fosab genetic axis is crucial for coordinating CM proliferation and scar tissue removal during zebrafish heart regeneration.

Notch signalling restricts inflammation and serpine1 expression in the dynamic endocardium of the regenerating zebrafish heart

“…6J). Both genes were shown to be expressed in dedifferentiated, proliferating cardiomyocytes in fish (Aguirre et al, 2014;Beauchemin et al, 2015), suggesting that changes in mycb and fosab expression might be associated with the reduction in cardiomyocyte proliferation in Notch-abrogated hearts. RNA-seq analysis indicated an upregulation of genes encoding sarcomere assembly and function proteins (Fig.…”

Zebrafish fin and heart: what's special about regeneration?

“…The only factor known to be involved in this process so far is a microRNA (miR-101a), whose expression is downregulated shortly after heart injury, which appears to be necessary to allow cardiomyocyte cell cycle re-entry to occur. Expression is upregulated again at 7 days post injury and suppression of miR-101a activity during the latter period results in defects in scar removal [64 ]. Both effects of miR-101a appear to be mediated by its suppression of the transcription factor fos, which is required for cardiomyocyte proliferation, yet acts as an inhibitor of scar tissue clearance [64 ].…”

“…Expression is upregulated again at 7 days post injury and suppression of miR-101a activity during the latter period results in defects in scar removal [64 ]. Both effects of miR-101a appear to be mediated by its suppression of the transcription factor fos, which is required for cardiomyocyte proliferation, yet acts as an inhibitor of scar tissue clearance [64 ].…”

Cell migration during heart regeneration in zebrafish

“…This now widely used method demonstrated that even after significant injury, such as surgical removal of 20% of the ventricle; the heart has the ability to fully regenerate (Poss et al, 2002). After resection, a fibrin clot seals the wound, and collagen is deposited (Poss et al, 2002; Beauchemin et al, 2015). However, over the course of 1–2 months, the scar is cleared and the myocardial layer is regenerated (Poss et al, 2002; Raya et al, 2003).…”

“…Compared with extrinsic signals, our knowledge about intrinsic programs that regulate cardiomyocyte proliferation is limited to several microRNAs (Yin et al, 2012; Beauchemin et al, 2015), and cardiac transcription factors gata4 (Kikuchi et al, 2010) and hand2 (Schindler et al, 2014). It is still largely unknown how these intrinsic programs are linked to extrinsic signals, however, a recent study showed a functional link between extrinsic (Nrg1) and intrinsic ( gata4 ) programs.…”