title: Differential regulation of the cardiac sodium calcium exchanger promoter in adult and neonatal cardiomyocytes by Nkx2.5 and serum response factor.
abstract: Nkx2.5 and serum response factor (SRF) are critically important transcription factors in cardiac morphogenesis. They are also widely expressed in adult cardiomyocytes, but there is little data to indicate their possible role in adult cardiac cells. In this paper we demonstrate that the interaction of Nkx2.5 and SRF in cardiac-specific gene regulation is different between neonatal and adult cardiomyocytes. Our experimental model utilizes transient transfection and adenovirus mediated gene transfer of the proximal promoter fragment of the cardiac isoform of the sodium-calcium exchanger gene (NCX1). This promoter construct (NCX184) contains a single Nkx2.5-response element (NKE) and a single serum response element (CArG). In rat neonatal cardiomyocytes NCX184 activity is substantially induced with Nkx2.5 or SRF and additively with both. Mutagenesis of these NKE and CArG elements demonstrated the specificity of the interactions, which was confirmed with gel retardation analysis of cardiac ventricular tissue. In contrast, in adult cardiomyocytes, co-infection of Nkx2.5 and SRF adenovirus vectors showed Nkx2.5 induction but SRF did not have additive effects on NCX1 promoter regulation. As opposed to NCX1, the proximal atrial natriuretic factor (ANF) promoter was regulated identically in response to SRF and Nkx2.5 in both adult and neonatal cardiomyocytes. These results show that Nkx2.5-SRF interactions are capable of producing different transcriptional responses in adult versus neonatal cardiomyocytes, implying important differences in NCX1 promoter tertiary complex formation dependent on developmental stage.
authors.affiliation: Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
authors.forename: Joachim G
authors.initials: JG
authors.lastname: Müller
authors.forename: Jerry T
authors.initials: JT
authors.lastname: Thompson
authors.forename: Angela M
authors.initials: AM
authors.lastname: Edmonson
authors.forename: Mary S
authors.initials: MS
authors.lastname: Rackley
authors.forename: Hideko
authors.initials: H
authors.lastname: Kasahara
authors.forename: Seigo
authors.initials: S
authors.lastname: Izumo
authors.forename: Tim C
authors.initials: TC
authors.lastname: McQuinn
authors.forename: Donald R
authors.initials: DR
authors.lastname: Menick
authors.forename: Terrence X
authors.initials: TX
authors.lastname: O'Brien
mesh_terms: D000818:Animals; D001665:Binding Sites; D002415:Cats; D004247:DNA / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D026362:Serum Response Factor / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D014157:Transcription Factors; D014161:Transduction, Genetic; D014162:Transfection; D029867:Xenopus Proteins
chemical_list: D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C095552:NKX2-5 protein, human; C484469:Nkx2-5 protein, mouse; D026362:Serum Response Factor; D019831:Sodium-Calcium Exchanger; D014157:Transcription Factors; D029867:Xenopus Proteins; D004247:DNA