Identification and characterization of embryonic stem cell-derived pacemaker and atrial cardiomyocytes

SPECIFIC AIMSLittle is known about the characteristics of individual cardiac cell types during early embryonic development because of the very small size of the heart tube, a lack of morphological differences, and the expression of specific markers. The aim of this study was the identification and functional characterization of cardiac subtypes during early stages of development. For this purpose, we used the embryonic stem (ES) cell in vitro differentiation system.PRINCIPAL FINDINGS1. α-MHC promoter-driven EGFP expression pattern in EBsTo identify early cardiomyocytes, transgenic ES cells were generated using the α-myosin heavy chain promoter, driving the expression of the enhanced green fluorescent protein (EGFP). EGFP expression was not detected at the ES cell stage or in EBs until day 7 of development. EGFP-positive areas were observed on the first or second day after plating (day 8/day 9); these started to beat spontaneously ∼ 1 day later. The most remarkable feature was the large diversity of EGFP f...