Mammals and birds have a specialized cardiac atrioventricular conduction system enabling rapid activation of both ventricles. This system may have evolved together with high heart rates to support their endothermic state (warm-bloodedness) and is seemingly lacking in ectothermic vertebrates from which first mammals then birds independently evolved. Here, we studied the conduction system in crocodiles (Alligator mississippiensis), the only ectothermic vertebrates with a full ventricular septum. We identified homologues of mammalian conduction system markers (Tbx3-Tbx5, Scn5a, Gja5, Nppa-Nppb) and show the presence of a functional atrioventricular bundle. The ventricular Purkinje network, however, was absent and slow ventricular conduction relied on trabecular myocardium, as it does in other ectothermic vertebrates. We propose the evolution of the atrioventricular bundle followed full ventricular septum formation prior to the development of high heart rates and endothermy. In contrast, the evolution of the ventricular Purkinje network is strongly associated with high heart rates and endothermy.
- Klíčová slova
- American alligator, Tbx3, Ventricular septum, conduction system, developmental biology, evolution, evolutionary biology, genomics, stem cells,
- MeSH
- aligátoři a krokodýli embryologie genetika fyziologie MeSH
- embryo nesavčí metabolismus MeSH
- Hisův svazek embryologie metabolismus fyziologie MeSH
- hybridizace in situ MeSH
- mezikomorová přepážka embryologie metabolismus fyziologie MeSH
- modely kardiovaskulární MeSH
- převodní systém srdeční embryologie fyziologie MeSH
- proteiny T-boxu genetika metabolismus MeSH
- Purkyňova vlákna embryologie metabolismus fyziologie MeSH
- srdce embryologie fyziologie MeSH
- srdeční frekvence genetika fyziologie MeSH
- srdeční komory embryologie metabolismus MeSH
- vývojová regulace genové exprese MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- proteiny T-boxu MeSH
