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A molecular clock regulates angiopoietin-like protein 2 expression.

Kadomatsu T, Uragami S, Akashi M, Tsuchiya Y, Nakajima H, Nakashima Y, Endo M, Miyata K, Terada K, Todo T, Node K, Oike Y - PLoS ONE (2013)

Bottom Line: Promoter activity of the human ANGPTL2 gene was significantly induced by CLOCK and BMAL1, an induction markedly attenuated by CRY co-expression.We also identified functional E-boxes in the ANGPTL2 promoter and observed occupancy of these sites by endogenous CLOCK in human osteosarcoma cells.Taken together, these data suggest that periodic expression of ANGPTL2 is regulated by a molecular clock.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan. tkado@gpo.kumamoto-u.ac.jp

ABSTRACT
Various physiological and behavioral processes exhibit circadian rhythmicity. These rhythms are usually maintained by negative feedback loops of core clock genes, namely, CLOCK, BMAL, PER, and CRY. Recently, dysfunction in the circadian clock has been recognized as an important foundation for the pathophysiology of lifestyle-related diseases, such as obesity, cardiovascular disease, and some cancers. We have reported that angiopoietin-like protein 2 (ANGPTL2) contributes to the pathogenesis of these lifestyle-related diseases by inducing chronic inflammation. However, molecular mechanisms underlying regulation of ANGPTL2 expression are poorly understood. Here, we assess circadian rhythmicity of ANGPTL2 expression in various mouse tissues. We observed that ANGPTL2 rhythmicity was similar to that of the PER2 gene, which is regulated by the CLOCK/BMAL1 complex. Promoter activity of the human ANGPTL2 gene was significantly induced by CLOCK and BMAL1, an induction markedly attenuated by CRY co-expression. We also identified functional E-boxes in the ANGPTL2 promoter and observed occupancy of these sites by endogenous CLOCK in human osteosarcoma cells. Furthermore, Cry-deficient mice exhibited arrhythmic Angptl2 expression. Taken together, these data suggest that periodic expression of ANGPTL2 is regulated by a molecular clock.

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Periodicity of Angptl2 mRNA and protein expression in epididymal WAT.A and B, Temporal expression profiles of Angptl2 mRNA in epididymal WAT of mice housed under light/dark cycles (A) or under constant darkness (B). C, Upper panel: Representative image of immunoblotting of ANGPTL2 protein in epididymal WAT. Hsc70 served as a control. Lower panel: Quantification of ANGPTL2 protein levels relative to Hsc70. For mice housed under constant darkness, circadian time (CT) was used instead of Zeitgeber time. The average expression level of mRNA or protein across all time points was set to 1. Data are expressed as means ± S.E.M. (n  =  3–5 mice for each data point).
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pone-0057921-g002: Periodicity of Angptl2 mRNA and protein expression in epididymal WAT.A and B, Temporal expression profiles of Angptl2 mRNA in epididymal WAT of mice housed under light/dark cycles (A) or under constant darkness (B). C, Upper panel: Representative image of immunoblotting of ANGPTL2 protein in epididymal WAT. Hsc70 served as a control. Lower panel: Quantification of ANGPTL2 protein levels relative to Hsc70. For mice housed under constant darkness, circadian time (CT) was used instead of Zeitgeber time. The average expression level of mRNA or protein across all time points was set to 1. Data are expressed as means ± S.E.M. (n  =  3–5 mice for each data point).

Mentions: Next, we examined Angptl2 mRNA expression in mouse epididymal WAT under constant darkness conditions. Real-time PCR analysis revealed that Angptl2 mRNA expression showed a similar oscillatory expression pattern under constant darkness conditions as it did under light-dark cycles (Figure 2A and B). Interestingly, Angptl2 mRNA expression exhibited a circadian pattern not only in epididymal fat but also in subcutaneous fat, liver, heart, and aorta (Figure S1). ANGPTL2 protein levels in WAT also showed a circadian pattern, with levels peaking between ZT 10 and ZT 14 and between ZT 34 and ZT 38 (Figure 2C). Overall, these data suggest that Angptl2 expression in vivo is regulated by a circadian clock.


A molecular clock regulates angiopoietin-like protein 2 expression.

Kadomatsu T, Uragami S, Akashi M, Tsuchiya Y, Nakajima H, Nakashima Y, Endo M, Miyata K, Terada K, Todo T, Node K, Oike Y - PLoS ONE (2013)

Periodicity of Angptl2 mRNA and protein expression in epididymal WAT.A and B, Temporal expression profiles of Angptl2 mRNA in epididymal WAT of mice housed under light/dark cycles (A) or under constant darkness (B). C, Upper panel: Representative image of immunoblotting of ANGPTL2 protein in epididymal WAT. Hsc70 served as a control. Lower panel: Quantification of ANGPTL2 protein levels relative to Hsc70. For mice housed under constant darkness, circadian time (CT) was used instead of Zeitgeber time. The average expression level of mRNA or protein across all time points was set to 1. Data are expressed as means ± S.E.M. (n  =  3–5 mice for each data point).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3585275&req=5

pone-0057921-g002: Periodicity of Angptl2 mRNA and protein expression in epididymal WAT.A and B, Temporal expression profiles of Angptl2 mRNA in epididymal WAT of mice housed under light/dark cycles (A) or under constant darkness (B). C, Upper panel: Representative image of immunoblotting of ANGPTL2 protein in epididymal WAT. Hsc70 served as a control. Lower panel: Quantification of ANGPTL2 protein levels relative to Hsc70. For mice housed under constant darkness, circadian time (CT) was used instead of Zeitgeber time. The average expression level of mRNA or protein across all time points was set to 1. Data are expressed as means ± S.E.M. (n  =  3–5 mice for each data point).
Mentions: Next, we examined Angptl2 mRNA expression in mouse epididymal WAT under constant darkness conditions. Real-time PCR analysis revealed that Angptl2 mRNA expression showed a similar oscillatory expression pattern under constant darkness conditions as it did under light-dark cycles (Figure 2A and B). Interestingly, Angptl2 mRNA expression exhibited a circadian pattern not only in epididymal fat but also in subcutaneous fat, liver, heart, and aorta (Figure S1). ANGPTL2 protein levels in WAT also showed a circadian pattern, with levels peaking between ZT 10 and ZT 14 and between ZT 34 and ZT 38 (Figure 2C). Overall, these data suggest that Angptl2 expression in vivo is regulated by a circadian clock.

Bottom Line: Promoter activity of the human ANGPTL2 gene was significantly induced by CLOCK and BMAL1, an induction markedly attenuated by CRY co-expression.We also identified functional E-boxes in the ANGPTL2 promoter and observed occupancy of these sites by endogenous CLOCK in human osteosarcoma cells.Taken together, these data suggest that periodic expression of ANGPTL2 is regulated by a molecular clock.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan. tkado@gpo.kumamoto-u.ac.jp

ABSTRACT
Various physiological and behavioral processes exhibit circadian rhythmicity. These rhythms are usually maintained by negative feedback loops of core clock genes, namely, CLOCK, BMAL, PER, and CRY. Recently, dysfunction in the circadian clock has been recognized as an important foundation for the pathophysiology of lifestyle-related diseases, such as obesity, cardiovascular disease, and some cancers. We have reported that angiopoietin-like protein 2 (ANGPTL2) contributes to the pathogenesis of these lifestyle-related diseases by inducing chronic inflammation. However, molecular mechanisms underlying regulation of ANGPTL2 expression are poorly understood. Here, we assess circadian rhythmicity of ANGPTL2 expression in various mouse tissues. We observed that ANGPTL2 rhythmicity was similar to that of the PER2 gene, which is regulated by the CLOCK/BMAL1 complex. Promoter activity of the human ANGPTL2 gene was significantly induced by CLOCK and BMAL1, an induction markedly attenuated by CRY co-expression. We also identified functional E-boxes in the ANGPTL2 promoter and observed occupancy of these sites by endogenous CLOCK in human osteosarcoma cells. Furthermore, Cry-deficient mice exhibited arrhythmic Angptl2 expression. Taken together, these data suggest that periodic expression of ANGPTL2 is regulated by a molecular clock.

Show MeSH
Related in: MedlinePlus