Properties of cardiac myocytes derived from hESCs with diminished B2M expression. The top row shows a typical appearance of a differentiated G-Mod cardiomyocyte layer in a phase-contrast (A) and a fluorescence mode (B). The presence of GCaMP sensor in G-Mod cells enables direct monitoring of rhythmical cell contractions upon cardiac lineage differentiation seen as transient increases in endogenous cell fluorescence. The panel
(C) shows sarcomeric alpha-actinin immunostaining with regular striations indicative of proper structural development. The panel
(D) illustrates changes in relative expression levels of pluripotency (NANOG, Oct3/4), mesodermal (TBX5), early and late (alpha-actin, GATA4, NkX2.5, alpha-2 actinin, myosin heavy-chain 6) markers in samples acquired on day 1, 7, and 21 of cardiac differentiation protocol (n = 3). The panel
(E) shows 3D cardiac fiber composed of G-Mod cardiac myocytes with the trace of calcium transients acquired from it to illustrate regular spontaneous contractions.