Figure 1.

DAPT Increases Calcium Flux, Sarcomere Structure, and Spontaneous Beating in iCLMs

(A) Experimental strategy for drug screening to enhance cardiac reprogramming.

(B) Quantification of the number of αMHC-GFP-positive MEFs after 7 days of reprogramming by GHMT and treatment with the indicated chemicals. Values are shown as relative to the mock control; n = 3 biological replicates.

(C) αMHC-GFP MEFs were infected with GHMT, and treated with DMSO or DAPT for 2 weeks. Analysis by qPCR of the mRNA expression of the indicated genes, relative to expression in DMSO-treated cells; n = 3 biological replicates.

(D) Quantification of the number of cells positive for cTnT and α-actinin by immunostaining; n = 3 biological replicates.

(E) Representative image of the immunostaining quantified in (D). Scale bar, 200 μm.

(F) Representative confocal images of immunostaining against α-actinin showing sarcomere structure in iCLMs (treated with DMSO or DAPT) and mouse adult cardiomyocytes. The percentage of cells presenting a sarcomere structure is shown in the upper-right corner of every panel. Scale bar, 20 μm.

(G) Quantification of the percentage of α-actinin-positive cells with sarcomeric structure. The average of three different experiments is shown, with a total n = 471 in vehicle-treated cells and n = 570 in DAPT-treated cells.

(H) Percentage of beating cells, relative to the number of input cells at indicated times; n = 3 biological replicates.

(I) Quantification of Ca²⁺ flux-positive GCaMP3 cells after 2 weeks of reprogramming; n = 3 biological replicates.

(J) Quantification of Ca²⁺ flux-positive MEFs treated with 4-Fluo AM dye after 2 weeks of reprogramming; n = 3 biological replicates.

Data are presented as mean ± SD. ^∗p < 0.05, ^∗∗p < 0.01. See also Figures S1–S3 and Table S1.