A myocyte enhancer factor 2 (MEF2) site located in a hypersensitive region of the FGF16 gene locus is required for preferential promoter activity in neonatal cardiac myocytes

Fibroblast growth factor 16 (FGF16) is preferentially expressed in the heart after birth, suggesting its regulation is associated with tissue-specific chromatin remodeling and DNA-protein interactions. Here we have mapped the transcription initiation site of murine FGF16 to approximately 1.1 kilobases (kb) upstream of the translation start codon (ATG). Hybrid reporter genes directed by about 4.7 kb of upstream FGF16 DNA were expressed specifically in transfected neonatal rat cardiac myocytes, as well as in the heart of transgenic mice. A DNaseI hypersensitive site was mapped to a region about 1.2 kb upstream of the transcription initiation site in heart but not kidney tissue, and a nuclease protection assay gave evidence of a cardiac-specific protein-DNA interaction in this region. Deletion analysis indicated that a hybrid gene with 1205 bp but not 1054 bp of upstream DNA directed FGF16 promoter activity in transfected neonatal rat cardiac myocytes. We identified a putative myocyte enhancer factor 2 (MEF2)-binding site at nucleotides -1159/-1148, confirmed by electrophoretic mobility shift assay and MEF2 antibody binding. Mutation of the MEF2 site resulted in a blunting of FGF16 promoter activity in transfected neonatal rat cardiac myocytes. These data suggest that chromatin remodeling and MEF2 binding in the FGF16 promoter contribute to expression in the postnatal heart.