| Summary: | Summary: When pluripotency factors are removed, embryonic stem cells (ESCs) undergo spontaneous differentiation, which, among other lineages, also gives rise to cardiac sublineages, including chamber cardiomyocytes and pacemaker cells. Such heterogeneity complicates the use of ESC-derived heart cells in therapeutic and diagnostic applications. We sought to direct ESCs to differentiate specifically into cardiac pacemaker cells by overexpressing a transcription factor critical for embryonic patterning of the native cardiac pacemaker (the sinoatrial node). Overexpression of SHOX2 during ESC differentiation upregulated the pacemaker gene program, resulting in enhanced automaticity in vitro and induced biological pacing upon transplantation in vivo. The accentuated automaticity is accompanied by temporally evolving changes in the effectors and regulators of Wnt signaling. Our findings provide a strategy for enriching the cardiac pacemaker cell population from ESCs. : Cho and colleagues show that heterologous SHOX2 expression boosts the differentiation of embryonic stem cells to cardiac pacemaker cells from embryonic stem cells by enhancing pacemaker cell-specific electrophysiology. Implantation of SHOX2-overxpressing embryoid bodies to the rat heart in vivo creates biological pacing. The SHOX2-facilitated pacemaker cell phenotype correlates with specific Wnt modulation, suggesting that Wnt may be a negotiator for cardiac subtype specification.
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