Axenfeld-Rieger Syndrome-associated Mutants of the Transcription Factor FOXC1 Abnormally Regulate in Model Zebrafish Embryos

FOXC1 is a member of the forkhead family of transcription factors, and whose function is poorly understood. A variety of mutants have been identified in patients diagnosed with the autosomal dominant disease Axenfeld-Rieger syndrome, which is mainly characterized by abnormal development of the eyes, particularly those who also have accompanying congenital heart defects (CHD). However, the role of FOXC1 in CHD, and how these mutations might impact FOXC1 function, remains elusive. Our previous work provided one clue to possible function, demonstrating that zebrafish , an orthologue of human essential for heart development, directly regulates the expression of , encoding a transcriptional regulator of cardiac progenitor cells. Abnormal expression of leads to CHD in mice and is also associated with CHD patients. Whether this link extends to the human system, however, requires investigation. In this study, we demonstrate that FOXC1 does regulate human expression in a dose-dependent manner via direct binding to its proximal promoter. A comparison of FOXC1 mutant function in the rat cardiac cell line H9c2 and zebrafish embryos suggested that the zebrafish embryos might serve as a more representative model system than the H9c2 cells. Finally, we noted that three of the Axenfeld-Rieger syndrome FOXC1 mutations tested increased, whereas a fourth repressed the expression of These results imply that mutant FOXC1s might play etiological roles in CHD by abnormally regulating in the patients. And zebrafish embryos can serve as a useful platform for rapidly evaluating disease-causing roles of mutated genes.