Abstract 14304: The Role of Foxc1 During the Differentiation of Embryonic Stem Cells Into Functional Cardiomyocytes
Background: Embryonic Stem Cells (ESCs) hold great potential for regeneration of damaged myocardium, however the molecular circuitry that guides ESC differentiation into cardiac lineages remains poorly understood. This is exemplified by the elusive role of the developmental transcription factor, Foxc1, during cardiac development. When one human FoxC1 allele is mutated it causes Axenfeld-Rieger syndrome characterized by ocular defects and often heart defects. Foxc1 homozygous null mice are either embryonic lethal or die soon after birth with the majority of these mice containing severe heart malformations. The only known Foxc1 target during heart development is Tbx1, a transcription factor necessary for the proper alignment of the outflow tract. Because Foxc1 null mice contain heart defects that are far more severe than Tbx1 null mice, it is likely that foxc1 has additional regulatory roles in heart development. It is unknown in which specific cell types of the heart Foxc1 functions.
Hypothesis: Foxc1 is critical for ESC differentiation into functional cardiomyocytes through the regulation of a downstream regulatory transcription network.
Methods and Results: Using a murine Nkx2.5-GFP reporter ESC line, we show that Foxc1 knockdown (KD) reduces the number of Nkx2.5+ cells upon differentiation. Foxc1 KD also reduces a panel of cardiomyocyte marker transcripts as well as inhibits the beating of embryoid bodies (EBs). On the other hand, using an inducible Foxc1 overexpression (OE) ESC line, we show that Foxc1 OE increases a panel of cardiomyocyte transcripts and enhances the number beating of EBs. Additionally, Foxc1 OE beating EBs have an enhanced spontaneous beat rate and possess functional electrophysiological properties, beating in synchrony with surrounding cardiomyocytes upon electrical stimulation. RNA-sequencing results identify over 3,000 differentially regulated transcripts after Foxc1 OE during cardiomyogenesis.
Conclusion: Both molecular and functional analyses reveal a positive correlation between Foxc1 expression level and cardiomyogenesis. Currently chromatin-immunoprecipitation sequencing is being performed to determine the direct downstream regulatory network of Foxc1 during cardiomyogenesis.
Author Disclosures: E. Lambers: None. B. Arnone: None. A. Fatima: None. J.A. Wasserstrom: None. G. Qin: None. T. Kume: None.
- © 2015 by American Heart Association, Inc.