Single nucleus RNA-seq of cardiomyocytes from neonatal mouse hearts after injury

The adult mammalian heart is incapable of regeneration following injury. In contrast, the neonatal mouse heart can efficiently regenerate during the first week of life. The molecular mechanisms that mediate the regenerative response and its blockade in later life are not understood. Here, by single-nucleus RNA sequencing, we map the dynamic transcriptional landscape of five distinct cardiomyocyte populations in healthy, injured and regenerating mouse hearts. We identify immature cardiomyocytes that enter the cell-cycle following injury and disappear as the heart loses the ability to regenerate. These proliferative neonatal cardiomyocytes display a unique transcriptional program dependent on NFYa and NFE2L1 transcription factors, which exert proliferative and protective functions, respectively. Cardiac overexpression of these two factors conferred protection against ischemic injury in mature mouse hearts that were otherwise non-regenerative. These findings advance our understanding of the cellular basis of neonatal heart regeneration and reveal a transcriptional landscape for heart repair following injury. We performed myocardial infarction (MI) or sham surgeries to mouse hearts at postnatal day 1 or day 8. At 1d and 3d post P1 and P8 surgery, ventricle samples below the surgery plane were collected for single nucleus RNA-Seq.