A Positive GATA Element and a Negative Vitamin D Receptor-Like Element Control Atrial Chamber-Specific Expression of a Slow Myosin Heavy-Chain Gene during Cardiac Morphogenesis

Abstract

We have used the slow myosin heavy chain (MyHC) 3 gene to study the molecular mechanisms that control atrial chamber-specific gene expression. Initially, slow MyHC 3 is uniformly expressed throughout the tubular heart of the quail embryo. As cardiac development proceeds, an anterior-posterior gradient of slow MyHC 3 expression develops, culminating in atrial chamber-restricted expression of this gene following chamberization. Two cis elements within the slow MyHC 3 gene promoter, a GATA-binding motif and a vitamin D receptor (VDR)-like binding motif, control chamber-specific expression. The GATA element of the slow MyHC 3 is sufficient for expression of a heterologous reporter gene in both atrial and ventricular cardiomyocytes, and expression of GATA-4, but not Nkx2-5 or myocyte enhancer factor 2C, activates reporter gene expression in fibroblasts. Equivalent levels of GATA-binding activity were found in extracts of atrial and ventricular cardiomyocytes from embryonic chamberized hearts. These observations suggest that GATA factors positively regulate slow MyHC 3 gene expression throughout the tubular heart and subsequently in the atria. In contrast, an inhibitory activity, operating through the VDR-like element, increased in ventricular cardiomyocytes during the transition of the heart from a tubular to a chambered structure. Overexpression of the VDR, acting via the VDR-like element, duplicates the inhibitory activity in ventricular but not in atrial cardiomyocytes. These data suggest that atrial chamber-specific expression of the slow MyHC 3 gene is achieved through the VDR-like inhibitory element in ventricular cardiomyocytes at the time distinct atrial and ventricular chambers form.The vertebrate heart, which initially forms as a linear, tubular structure, undergoes a complex series of morphogenetic movements to form a multichambered organ. The low-pressure atrial and high-pressure ventricular chambers which are formed differ in morphology, electrophysiology, and the repertoire of muscle contractile protein genes which are expressed (8,30). The developmental and molecular mechanisms responsible for establishing and maintaining chamber-specific differences are largely unknown.In adult animals, several members of contractile protein gene families show chamber-restricted or strong chamber-preferential expression. The myosin heavy-chain (MyHC) AMHC1 and slow MyHC 3 genes (56, 60), the myosin light-chain 1a (MLC-1a) and MLC-2a genes (21,31), and the atrial natriuretic factor (ANF) gene (61) show atrial specificity. In small mammals, the ␣-MyHC gene exhibits an atrial chamber preference of expression before birth (31). Conversely, MLC-2v

Vitamin D deficiency and myocardial diseases

“…These effects on myosin gene expression might partially underlie the associations of vitamin D status and myocardial contractility, which have been observed in rodents [45][46][47].…”

“…Expression of myosin, a major contractile protein of the myocardium, is also regulated by vitamin D [45][46][47]. These effects on myosin gene expression might partially underlie the associations of vitamin D status and myocardial contractility, which have been observed in rodents [45][46][47].…”

Tissue-specific GATA factors are transcriptional effectors of the small GTPase RhoA

“…It has been shown previously that GATA-4 regulates the expression of many contractile proteins, such as ␣-myosin heavy-chain, ␤-myosin heavy-chain, and cardiac troponin I in cardiomyocytes ) and activates the promoter of several contractile protein genes, such as cardiac troponin C, slow myosin heavy-chain, and cardiac ␣-actin, alone or in combination with other transcription factors (Ip et al 1994;Molkentin et al 1994;Murphy et al 1997;Sepulveda et al 1998;G.F. Wang et al 1998;Morin et al 2000).…”

GATA-4 Gene Organization and Analysis of Its Promoter

“…Since knockout mice exhibited specification of the cardiac cell lineage, 3,4) and ES cells with homozygous GATA-4(Ϫ/Ϫ) contributed to the heart tissue in chimeric embryos, 3) GATA-4 in procardiomyocytes or visceral endoderm cells likely regulate the expression of a morphogenic signaling molecule(s) that directs the migration of procardiomyocytes. Although GATA-4 knockout mice express cardiac contractile proteins, 3,4) a number of studies have suggested that both structural and regulatory genes in the cardiac muscle cells are targets of GATA-4, such as those of A1 adenosine receptor, 5) angiotensin II type Ia receptor, 6) atrial natriuretic peptide, 7) brain natriuretic peptide, [7][8][9] cardiac a actin, 10) cardiac troponin C, 11) cardiac troponin I, 9) cardiac-restricted ankyrin repeat protein, 12) amyosin heavy-chain, 9,13) b-myosin heavy-chain, 9) myosin light chain 1/3, 14) Na ϩ /Ca 2ϩ exchanger 1, 15,16) Nkx-2.5, 17,18) slow myosin heavy chain, 19) and corin. 20) It is also evident that GATA-4 functions in the regulation of both epithelial cell differentiation and gene expression in the gut 21,22) and gonads [23][24][25][26][27] in addition to the heart.…”