Purkinje cardiomyocytes of the ventricular conduction system are highly diploid but not regenerative
Watanabe, H.; Tao, G.; Gan, P.; Westbury, B. C.; Cox, K. D.; Tjen, K.; Song, R.; Fishman, G. I.; Makita, T.; Sucov, H. M.
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Inefficiency of regeneration underlies many of the pathologies associated with heart injury and disease. Ventricular diploid cardiomyocytes (CMs) are a candidate population that may have enhanced proliferative and regenerative properties [1-3], but subpopulations of diploid CMs and their regenerative capacities are not yet known. Here, using the expression marker Cntn2-GFP and the lineage marker Etv1CreERT2, we demonstrate that peripheral ventricular conduction CMs (Purkinje CMs) are disproportionately diploid (35%, vs. 4% of bulk ventricular CMs). However, this lineage had no enhanced competence to support regeneration after adult infarction. Furthermore, the CM-specific kinase Tnni3k, which strongly influences bulk ventricular CM ploidy [3] and is also associated with conduction system defects [4], had no influence on the ploidy or organization of the ventricular conduction system. Unlike the bulk diploid CM population, a significant fraction of conduction CMs remain diploid by avoiding neonatal cell cycle activity, likely contributing to these properties.
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