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2. Numerical Performance of a Tensor MUSIC Algorithm Based on HOSVD for a Mixture of Polarized Sources

Author

Boizard, M., Ginolhac, G., Frederic Pascal, Miron, S., Forster, P., Systèmes et Applications des Technologies de l'Information et de l'Energie (SATIE), École normale supérieure - Cachan (ENS Cachan)-Université Paris-Sud - Paris 11 (UP11)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-École normale supérieure - Rennes (ENS Rennes)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Conservatoire National des Arts et Métiers [CNAM] (CNAM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Informatique, Systèmes, Traitement de l'Information et de la Connaissance (LISTIC), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Sondra, CentraleSupélec, Université Paris-Saclay (COmUE) (SONDRA), ONERA-CentraleSupélec-Université Paris Saclay (COmUE), Centre de Recherche en Automatique de Nancy (CRAN), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Ginolhac, Guillaume, and Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)

Subjects
[INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, [INFO.INFO-TS] Computer Science [cs]/Signal and Image Processing, DOA Polarimetric sources estimation, HOSVD, Tensor MUSIC, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, [SPI.SIGNAL] Engineering Sciences [physics]/Signal and Image processing
Abstract

International audience; In this paper, we develop an improved tensor MUSIC algorithm adapted to multidimensional data by means of multilinear algebra tools. This approach allows to preserve the multidimensional structure as the signal and the noise subspaces are estimated from the Higher Order Singular Value Decomposition (HOSVD) of the covariance tensor. The proposed algorithm is applied to a polarized source model. By computing the Mean Squared Error (MSE) for different scenarios, the performance of this method is compared to the classical MUSIC algorithm as well as the vector MUSIC algorithm that includes the polarization information. The simulations show that our algorithm outperforms the vector algorithms.

Published
2013
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3. Obesity-related overexpression of fatty-acid synthase gene in adipose tissue involves sterol regulatory element-binding protein transcription factors.

Author

Boizard, M, Le Liepvre, X, Lemarchand, P, Foufelle, F, Ferré, P, and Dugail, I

Abstract

Elevated lipogenesis is a key determinant of exaggerated fat deposition in adipose tissue of obese Zucker rats. We previously delineated a region in the fatty-acid synthase promoter, which was responsible for obesity-related overexpression of the fatty-acid synthase (FAS) gene, by negatively regulating the activity of the downstream promoter in lean but not obese rat fat cells. The present study aimed to identify the transcriptional factors acting on this target region. First, functional analysis of mutated FAS promoter constructs in transiently transfected lean and obese rat adipocytes showed that the activity of the obesity-related region relied on the presence of a transcriptionally inactive sterol regulatory element at -150, which counteracted activation through the downstream E-box. Adenovirus-mediated overexpression of a dominant negative form of adipocyte determination and differentiation factor 1 (ADD1) was used to neutralize endogenous ADD1/ sterol regulatory element-binding protein (SREBP) transcriptional activity in fat cells, by producing inactive dimers unable to bind target DNA. With this system, we observed that overexpression of FAS in obese rat adipocytes was ADD1/SREBP-dependent. SREBP isoforms expression was assessed in lean and obese rat fat cells and showed no differences in the level of ADD1/SREBP1 mRNA. In addition, equivalent amounts of immunoreactive ADD1/SREBP1 were found in nuclear extracts from lean and obese rat fat cells. In contrast, immunoreactive SREBP2, which was very low in nuclear extracts from lean rats, was induced in obese rat fat cells. Finally, using in vitro binding studies, we showed that SREBP2 was able to displace ADD1/SREBP1 binding from the sterol regulatory element (SRE) site. Thus, we propose a mechanism for obesity-related overexpression of FAS gene in rat adipocyte. ADD1/SREBP1-activated transcription proceeding from the E-box motif is counterbalanced by a negative SRE site acting by limiting the availability of ADD1/SREBP1 in normal fat cells. The negative effect of this site is abolished in obese rat adipocyte nuclei where SREBP2 is induced and can substitute for ADD1/SREBP1 binding to the inactive SRE. These results provide evidence for the implication of SREBPs in the dysregulation of adipocyte metabolism characteristic of the obese state.

Published
1998

4. Functional antagonism between inhibitor of DNA binding (Id) and adipocyte determination and differentiation factor 1/sterol regulatory element-binding protein-1c (ADD1/SREBP-1c) trans-factors for the regulation of fatty acid synthase promoter in adipocytes.

Author

Moldes M, Boizard M, Liepvre XL, Fève B, Dugail I, and Pairault J

Subjects
3T3 Cells, Adipocytes, Animals, Cell Differentiation genetics, Cyclic AMP pharmacology, DNA-Binding Proteins genetics, Gene Expression Regulation, Enzymologic, Genes, Reporter, Inhibitor of Differentiation Protein 1, Inhibitor of Differentiation Protein 2, Inhibitor of Differentiation Proteins, Mice, RNA, Messenger metabolism, Rats, Signal Transduction genetics, Sterol Regulatory Element Binding Protein 1, Transcription Factors genetics, fas Receptor genetics, CCAAT-Enhancer-Binding Proteins, DNA-Binding Proteins antagonists & inhibitors, Fatty Acid Synthases genetics, Neoplasm Proteins, Nuclear Proteins antagonists & inhibitors, Promoter Regions, Genetic, Repressor Proteins, Transcription Factors antagonists & inhibitors
Abstract

We show that Id (inhibitor of DNA binding) 2 and Id3, dominant negative members of the helix-loop-helix (HLH) family, interact with the adipocyte determination and differentiation factor 1 (ADD1)/sterol regulatory element-binding protein (SREBP) 1c, a transcription factor of the basic HLH-leucine zipper family that controls the expression of several key genes of adipose metabolism. Gel mobility-shift assays performed with in vitro-translated ADD1, Id2 or Id3 proteins and a fatty acid synthase (FAS) promoter oligonucleotide showed evidence for a marked inhibition of the formation of DNA-ADD1 complexes by Id2 or Id3 proteins. Co-immunoprecipitation studies using in vitro-translated proteins demonstrated further the physical interaction of Id and ADD1/SREBP-1c proteins in the absence of DNA. Using the FAS gene as a model of an ADD1-regulated promoter in transiently transfected isolated rat adipocytes or mature 3T3-L1 adipocytes, a potent inhibition of the activity of the FAS-chloramphenicol acetyltransferase reporter gene was observed by overexpression of Id2 or Id3. Reciprocally, co-transfection of Id3 antisense and ADD1 expression vectors in preadipocytes potentiated the ADD1/SREBP-1c effect on the FAS promoter activity. Finally, in the non adipogenic NIH-3T3 cell line, most of the ADD1-mediated trans-activation of the FAS promoter was counteracted by co-transfection of Id2 or Id3 expression vectors. Previous studies have indicated Id gene expression to be down-regulated during adipogenesis [Moldes, Lasnier, Fève, Pairault and Djian (1997) Mol. Cell. Biol. 17, 1796-1804]. We here demonstrated that there was a dramatic rise of Id2 and Id3 mRNA levels when 3T3-L1 adipocytes or isolated rat fat cells were exposed to lipolytic and anti-lipogenic agents, forskolin and isoproterenol. Taken together, our data show that Id products are functionally involved in modulating ADD1/SREBP-1c transcriptional activity, and thus lipogenesis in adipocytes.

Published
1999

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