ß-catenin drives distinct transcriptional networks in regenerative and non-regenerative cardiomyocytes

Quaife-Ryan GA1,2, Lavers G1,2, Mills RJ1,2, Voges HK1,2, Ramialison M3, Hudson JE1,2 and Porrello ER1,4,5

  1. School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia.
  2. QIMR Berghofer Medical Research Institute, Brisbane, QLD, 4006, Australia.
  3. Australian Regenerative Medicine Institute, Monash University, Clayton, VIC, 3800, Australia.
  4. Murdoch Children’s Research Institute, The Royal Children’s Hospital, Parkville, VIC, 3052, Australia.
  5. Department of Physiology, School of Biomedical Sciences, The University of Melbourne, Parkville, VIC, 3010, Australia.

The inability of the adult mammalian heart to regenerate following cardiac injury represents a major limitation in the management of heart failure. In comparison, the neonatal mouse heart regenerates following myocardial infarction (MI). We recently compared the neonatal and adult transcriptomes of multiple cardiac cell populations and uncovered a regenerative gene network associated with Wnt/β-catenin signalling. However, it is unclear what role Wnt/β-catenin signalling plays in driving the pro-regenerative network. Here, we study Wnt/β-catenin involvement in cardiomyocyte regeneration. We found that stimulation of β-catenin signalling by GSK3 inhibition (GSK3i) in immature human embryonic stem-cell-derived cardiomyocytes and 3D human cardiac organoids potently induced cardiomyocyte proliferation. Furthermore, β-catenin inhibition abrogated GSK3i-induced cardiomyocyte proliferation in vitro. To identify direct β-catenin transcriptional targets, we undertook RNA sequencing (RNA-seq) of GSK3i treated human cardiomyocytes combined with chromatin-immunoprecipitation sequencing (ChIP-seq) to reveal 22 direct β-catenin/TCF7L2 target genes that were shared in common between the human and mouse regenerative networks. Consistent with these results, delivery of constitutively active β-catenin (caBCAT) in vivo stimulated neonatal cardiomyocyte proliferation. Additionally, β-catenin inhibition limited neonatal cardiomyocyte cell cycle activity in vivo and downregulated β-catenin-target genes. However, in contrast to these effects in regenerative cardiomyocytes, caBCAT delivery to the adult mouse heart following MI did not induce cardiomyocyte proliferation, although cardiac function was improved. RNA-seq of purified adult cardiomyocytes treated with caBCAT uncovered a distinct transcriptional network associated with cardioprotection and modulation of the immune response that appears to be driven by FoxO. Therefore, β-catenin drives distinct transcriptional programs in regenerative and non-regenerative cardiomyocytes. Redirection of β-catenin to its pro-proliferative target genes could be exploited for regenerative applications in the future.