On the other hand, following myocardial infarction in adult mice and postnatal day 8 (P8) neonates, there was a robust upregulation of Acta2 expression by fibroblasts 3 days post injury, a feature which was absent in the adult zebrafish after cardiac injury (Supplementary Figure S2C). The gene discussed is ACTA2; the disease is myocardial infarction.