Purpose: The role of GATA5 in the morphogenesis of aortic valve has been recently elucidated in the mice knock out model. Growing evidence demonstrates that genetic defects in GATA5 might be responsible for various forms of congenital heart diseases (CHDs) in humans. The published results however were neither supported by functional data, nor by proper genetic controls. The aim of this proposal is to unravel the role of GATA5 in such diseases, and establish a well-defined genotype/phenotype association.
Methods: Blood was collected from children with CHD. Sanger sequencing was carried out on all coding exons of GATA5. Site directed mutagenesis was carried out on the corresponding human GATA5 cDNA and the generated expression vector was tested in transfected cells.
Results: One novel mutation (T67P) and another previously reported mutation (Y142H) have been identified in four out of 150 patients screened. Unlike all previously described mutations in GATA5, our mutations were homozygous. The T67P mutation in one patient is homozygous as a consequence of one inherited allele and another de novo mutated allele. The Y142H mutation is in the trans-activating domain of the GATA5 protein suggesting a direct effect on the transcriptional properties of the protein. In vitro assays, did show a consistent reproducible 30-40% drop in transcativtional activities over the corresponding GATA binding sites on different promoters.
Conclusion: We have characterized novel mutations in GATA5 and their associations with CHDs by proving that they lead to abnormal protein function. This is the first report on a homozygous mutation in a gene encoding a transcription factor linked to CHD. The results go in parallel with the knock-out mice proving that genetic results in mice are mirror-images for those in humans.