Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In situ hybridization studies, promoter analyses and antisense RNA experiments have implicated transcription factor GATA-4 in the regulation of cardiomyocyte differentiation. In this study, we utilized Gata4-/- embryonic stem (ES) cells to determine whether this transcription factor is essential for cardiomyocyte lineage commitment. First, we assessed the ability of Gata4-/- ES cells form cardiomyocytes during in vitro differentiation of embryoid bodies. Contracting cardiomyocytes were seen in both wild-type and Gata4-/- embryoid bodies, although cardiomyocytes were observed more often in wild type than in mutant embryoid bodies. Electron microscopy of cardiomyocytes in the Gata4-/- embryoid bodies revealed the presence of sarcomeres and junctional complexes, while immunofluorescence confirmed the presence of cardiac myosin. To assess the capacity of Gata4-/- ES cells to differentiate into cardiomyocytes in vivo, we prepared and analyzed chimeric mice. Gata4-/- ES cells were injected into 8-cell-stage embryos derived from ROSA26 mice, a transgenic line that expresses beta-galactosidase in all cell types. Chimeric embryos were stained with X-gal to discriminate ES cell- and host-derived tissue. Gata4-/- ES cells contributed to endocardium, myocardium and epicardium. In situ hybridization showed that myocardium derived from Gata4-/- ES cells expressed several cardiac-specific transcripts, including cardiac alpha-myosin heavy chain, troponin C, myosin light chain-2v, Nkx-2.5/Csx, dHAND, eHAND and GATA-6. Taken together these results indicate that GATA-4 is not essential for terminal differentiation of cardiomyocytes and suggest that additional GATA-binding proteins known to be in cardiac tissue, such as GATA-5 or GATA-6, may compensate for a lack of GATA-4.
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PMID:Cardiomyocyte differentiation by GATA-4-deficient embryonic stem cells. 936 31

The cardiac troponin I gene is one of the few sarcomeric protein genes exclusively expressed in cardiac muscle. We show here that this specificity is controlled by a proximal promoter (-230/+16) in transfected cardiac cells in culture, in the adult hearts, and in transgenic animals. Functional analysis indicates that MEF2/Oct-1, Sp1, and GATA regulatory elements are required for optimal gene activation because selective mutations produce weak or inactive promoters. MEF2 and Oct-1 transcription factors bind to the same A/T-rich element. A mutation that blocks this binding markedly reduces gene activation in vivo and in vitro, and overexpression of MEF2A, MEF2C, and MEF2D in noncardiac cells transactivates the cardiac troponin I promoter. Disruption of these elements inactivates the cardiac troponin I promoter in cultured cardiac cells but has a less important role in transfected adult heart. Moreover, nuclear extracts from an almost pure population of adult cardiac cells contain much lower levels of GATA binding activity compared with fetal cardiac cells. These findings point to a differential role of GATA factors in the maintenance of gene expression in the adult heart as compared with the activation of cardiac genes in fetal cardiomyocytes. Overexpression of GATA family members transactivates the cardiac troponin I promoter, and GATA-5 and GATA-6 are stronger transactivators than GATA-4, a property apparently unique to the cardiac troponin I promoter. Transgenic mice carrying the -230/+126 base pair promoter express beta-galactosidase reporter gene in the heart both at early stages of cardiogenesis and in the adult animals. These results indicate that the ability of the cardiac troponin I proximal promoter to target expression of a downstream gene in the heart is also maintained when the transgene is integrated into the genome.
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PMID:Combinatorial cis-acting elements control tissue-specific activation of the cardiac troponin I gene in vitro and in vivo. 973 4

Adenosine acts via A1 adenosine receptors (A1ARs) in the heart and brain to potently influence mammalian physiology. A1ARs are expressed very early in embryonic development, and A1ARs are among the earliest expressed G protein coupled receptors in the heart and brain. To understand the biologic basis of A1AR expression, a genomic fragment containing the murine A1AR promoter was cloned. Reporter assay studies using DDT1 MF2 cells that express A1ARs revealed that 500 base pairs of the proximal A1AR promoter contained essential elements for A1AR gene expression. Transgenic mice with A1AR proximal promoter coupled with the beta-galactosidase reporter gene had heavy labeling of the brain and atria, consistent with normal patterns of A1AR expression. Within the proximal A1AR promoter, putative binding sites for cardiac transcription factors GATA and Nkx2.5 were identified. Co-expression studies revealed that GATA-4 and Nkx2.5 could individually drive A1AR promoter activity and act synergistically to activate A1AR expression. These observations suggest that embryonic A1AR expression involves activation of the A1AR promoter by GATA-4 and Nkx2.5.
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PMID:Characterization of the murine A1 adenosine receptor promoter, potent regulation by GATA-4 and Nkx2.5. 1031 39

The Na(+)-Ca(2+) exchanger (NCX) regulates intracellular calcium homeostasis. We report on an upstream region of the rat NCX1 multipartite promoter that is active in cardiac myocytes. Although inactive in most non-cardiac cell lines, its activity can be rescued by cotransfection with GATA-4 and -6, but not GATA-5 transcription factors. In transgenic mice and similar to endogenous NCX1 mRNA expression, the upstream promoter region directs uniform beta-galactosidase expression in cardiac myocytes from approximately 7.75dpc. In adult mouse hearts, promoter activity is, however, significantly reduced and heterogeneous, except in the conduction system (sinoatrial and atrioventricular node, atrioventricular bundles). The upstream NCX1 promoter region thus directs appropriate spatial and temporal control of cardiac expression throughout development.
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PMID:A distant upstream region of the rat multipartite Na(+)-Ca(2+) exchanger NCX1 gene promoter is sufficient to confer cardiac-specific expression. 1173 Dec 39

Earlier work implicates transcription factors GATA-4 and GATA-6 in murine adrenal function. We have now studied their expression during mouse and human adrenal development in detail. GATA-4 and GATA-6 mRNAs and protein are readily detectable from embryonic d 14 and gestational wk 19 onwards in the mouse and human adrenal cortex, respectively. In the postnatal adrenal, GATA-4 expression is down-regulated, whereas GATA-6 mRNA and protein continue to be expressed. To clarify the significance of GATA-4 for early adrenocortical development, Gata4-/- ES cells were injected into eight-cell-stage embryos derived from ROSA26 mice, a transgenic line expressing beta-galactosidase in all cell types, including the adrenocortical cells. The resultant chimeric embryos were stained with X-gal to discriminate ES cell- and host-derived tissue. Gata4-/- cells contributed to adrenocortical cells in these chimeras, and these cells also expressed GATA-6. Taken together, our findings suggest that GATA-6 expression is needed throughout adrenal development from fetal to adult age. GATA-4, on the other hand, may serve a role in the fetal adrenal gene regulation, although it is not essential for early adrenocortical differentiation.
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PMID:Differential expression of GATA-4 and GATA-6 in fetal and adult mouse and human adrenal tissue. 1213 May 79

Sphingosine-1-phosphate is a bioactive sphingolipid that regulates proliferation, differentiation, migration, and apoptosis. Sphingosine-1-phosphate is irreversibly degraded by the highly conserved enzyme sphingosine-1-phosphate lyase. Recent studies have suggested that sphingosine-1-phosphate lyase expression affects animal development and cell fate decisions. Despite its crucial role, mechanisms affecting expression of sphingosine-1-phosphate lyase remain poorly understood. In this study, regulation of sphingosine-1-phosphate lyase gene expression was investigated in Caenorhabditis elegans, where lyase expression is spatially restricted to cells of the developing and adult gut and is essential for normal development. Deletion analysis and generation of transgenic worms combined with fluorescence microscopy identified a 350-nucleotide sequence upstream of the ATG start site necessary for maximal lyase expression in adult worms. Site-specific mutagenesis of a GATA transcription factor-binding motif in the promoter led to loss of reporter expression. Knockdown of the gut-specific GATA transcription factor ELT-2 by RNA interference similarly led to loss of reporter expression. ELT-2 interacted with the GATA factor-binding motif in vitro and was also capable of driving expression of a Caenorhabditis elegans lyase promoter-beta-galactosidase reporter in a heterologous yeast system. These studies demonstrate that ELT-2 regulates sphingosine-1-phosphate lyase expression in vivo. Additionally, we demonstrate that the human sphingosine-1-phosphate lyase gene is regulated by a GATA transcription factor. Overexpression of GATA-4 led to both an increase in activity of a reporter gene as well as an increase in endogenous sphingosine-1-phosphate lyase protein.
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PMID:Regulation of sphingosine-1-phosphate lyase gene expression by members of the GATA family of transcription factors. 1573 35

Cardiomyocytes expressing host markers, such as the Y chromosome in sex-mismatched transplants, have been described in human allografts, suggesting that circulating cells can contribute to cardiac regeneration. It has not been established, however, whether host-derived cardiomyocytes result from transdifferentiation of stem cells or cell fusion. To address this issue, we used heterotopic heart xenografts and looked for markers of donor and recipient cells. Golden Syrian hamsters or transgenic mice expressing nuclear beta-galactosidase under the control of the cardiac troponin I promoter served as organ donors, while GFP+ transgenic rats were used as recipients. GFP+ cells, including abundant CD-45+ inflammatory cells and rare undifferentiated cells expressing early cardiac markers (GATA-4 or MEF2C), were found in xenografts harvested two weeks after surgery. In addition, rare GFP+ mature cardiomyocytes were found in 7 of 8 hamster xenografts and 6 of 6 mouse xenografts. The proportion of these cells was very low (0.0001% to 0.0344% in hamster xenografts) but similar to the one observed in control rat heart allografts. Without exception, all GFP+ cardiomyocytes also expressed donor markers, i.e., hamster membrane antigens or lacZ, so they must derive from cell fusion, not transdifferentiation.
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PMID:Hybrid cardiomyocytes derived by cell fusion in heterotopic cardiac xenografts. 1707 78