BADERC- Evan Rosen

Evan Rosen, M.D., Ph.D.

Transcriptional Pathways in Adipogenesis

To understand tissue development one must understand the gene expression changes that occur during differentiation. In fat cell development, or adipogenesis, most of the focus has been on the transcription factors CCAAT box enhancer binding protein a (C/EBPa), peroxisome proliferator-activated receptor g (PPARg), and adipocyte determination and differentiation factor-1/ sterol regulatory element binding protein-1c (ADD1/SREBP1c). We are working to identify novel transcriptional pathways involved in adipose gene expression through the use of classic ‘promoter bashing’ approaches, functional screening of cDNA libraries, and comparative genomics. In addition to basic information about the control of tissue-specific gene expression, these studies will yield specific information about the regulation of biologically and medically relevant proteins expressed by fat cells.

We are using a fibroblast cell line that lacks the adipogenic factor PPARg to screen a retroviral adipocyte cDNA library for factors that can induce aspects of adipogenesis in the absence of PPARg. We are also studying a variety of adipose-selective promoters, such as those for leptin, adipsin, and adiponectin, to clarify the regulatory elements that participate in tissue-specific gene expression in adipocytes. Another strategy we are using involves a functional genomic approach, performed in collaboration with the Whitehead Genome Center and Dr. Eric Lander’s laboratory at MIT. We have collected several hundred genes expressed in fat cells, and we are performing comparisons of large genomic stretches flanking these genes, searching for recurring motifs that may represent conserved regulatory regions. These regions are then compared between mouse and human syntenic sequence to confirm their conservation. Sequences that emerge from these analyses will be used to identify binding proteins that may determine at least part of the tissue-specific gene expression seen in adipose cells.

References:

1. Wu Z, Rosen ED, Brun R, Hauser S, Adelmant G, Troy AE, McKeon C, Darlington GJ, and Spiegelman BM. Cross-regulation of C/EBPa and PPARg controls the transcriptional pathway of adipogenesis and insulin sensitivity. Molecular Cell. 1999; 3: 151-158.

2. Rosen ED, Sarraf P, Troy AE, Moore K., Bradwin G., Milstone DS, Spiegelman BM and Mortensen R. PPARg is required for the differentiation of adipose tissue in vivo and in vitro. Molecular Cell. 1999; 4: 611-617.

3. Moore K, Rosen ED, Fitzgerald ML, Randow F, Andersson LP, Altshuler D, Milstone DS, Mortensen RM, Spiegelman BM, and Freeman M. Role of PPARg in macrophage differentiation and cholesterol uptake. Nature Medicine. 2001; 7: 41-47.

4. Rosen ED, Hsu CH, Wang X, Sakai S, Freeman MW, Gonzalez FJ, and Spiegelman BM. C/EBPalpha induces adipogenesis through PPARgamma: a unified pathway. Genes and Development. 2002; 16:22-26.

5. Rosen ED and Spiegelman BM. Molecular regulation of adipogenesis. Annual Review of Cell and Developmental Biology, 2000; 16:145-171.

6. Rosen ED, Puigserver P, Walkey CJ, Spiegelman BM. Transcriptional control of adipogenesis. Genes and Development, 2000; 14: 1293-1307.

7. Rosen ED and Spiegelman BM. Peroxisome-proliferator-activated receptor gamma ligands and atherosclerosis: ending the heartache. Journal of Clinical Investigation, 2000; 106: 629-631.

8. Rosen ED, Spiegelman BM. PPARgamma: A nuclear regulator of metabolism, differentiation, and cell growth. J Biol Chem. 2001; 276: 37731-4.

9. Rosen ED, Hsu CH, Wang X, Sakai S, Freeman MW, Gonzalez FJ, Spiegelman BM. C/EBPalpha induces adipogenesis through PPARgamma: a unified pathway.Genes Dev. 2002;16:22-6.

10. Rosen ED. The molecular control of adipogenesis, with special reference to lymphatic pathology. Ann N Y Acad Sci. 2002;979:143-58; discussion 188-96.

11. Rosen ED, Kulkarni RN, Sarraf P, Ozcan U, Okada T, Hsu CH, Eisenman D, Magnuson MA, Gonzalez FJ, Kahn CR, Spiegelman BM. Targeted elimination of peroxisome proliferator-activated receptor gamma in beta cells leads to abnormalities in islet mass without compromising glucose homeostasis. Mol Cell Biol. 2003;23:7222-9.






			Evan Rosen, M.D., Ph.D. Transcriptional Pathways in Adipogenesis To understand tissue development one must understand the gene expression changes that occur during differentiation. In fat cell development, or adipogenesis, most of the focus has been on the transcription factors CCAAT box enhancer binding protein a (C/EBPa), peroxisome proliferator-activated receptor g (PPARg), and adipocyte determination and differentiation factor-1/ sterol regulatory element binding protein-1c (ADD1/SREBP1c). We are working to identify novel transcriptional pathways involved in adipose gene expression through the use of classic ‘promoter bashing’ approaches, functional screening of cDNA libraries, and comparative genomics. In addition to basic information about the control of tissue-specific gene expression, these studies will yield specific information about the regulation of biologically and medically relevant proteins expressed by fat cells. We are using a fibroblast cell line that lacks the adipogenic factor PPARg to screen a retroviral adipocyte cDNA library for factors that can induce aspects of adipogenesis in the absence of PPARg. We are also studying a variety of adipose-selective promoters, such as those for leptin, adipsin, and adiponectin, to clarify the regulatory elements that participate in tissue-specific gene expression in adipocytes. Another strategy we are using involves a functional genomic approach, performed in collaboration with the Whitehead Genome Center and Dr. Eric Lander’s laboratory at MIT. We have collected several hundred genes expressed in fat cells, and we are performing comparisons of large genomic stretches flanking these genes, searching for recurring motifs that may represent conserved regulatory regions. These regions are then compared between mouse and human syntenic sequence to confirm their conservation. Sequences that emerge from these analyses will be used to identify binding proteins that may determine at least part of the tissue-specific gene expression seen in adipose cells. References: 1. Wu Z, Rosen ED, Brun R, Hauser S, Adelmant G, Troy AE, McKeon C, Darlington GJ, and Spiegelman BM. Cross-regulation of C/EBPa and PPARg controls the transcriptional pathway of adipogenesis and insulin sensitivity. Molecular Cell. 1999; 3: 151-158. 2. Rosen ED, Sarraf P, Troy AE, Moore K., Bradwin G., Milstone DS, Spiegelman BM and Mortensen R. PPARg is required for the differentiation of adipose tissue in vivo and in vitro. Molecular Cell. 1999; 4: 611-617. 3. Moore K, Rosen ED, Fitzgerald ML, Randow F, Andersson LP, Altshuler D, Milstone DS, Mortensen RM, Spiegelman BM, and Freeman M. Role of PPARg in macrophage differentiation and cholesterol uptake. Nature Medicine. 2001; 7: 41-47. 4. Rosen ED, Hsu CH, Wang X, Sakai S, Freeman MW, Gonzalez FJ, and Spiegelman BM. C/EBPalpha induces adipogenesis through PPARgamma: a unified pathway. Genes and Development. 2002; 16:22-26. 5. Rosen ED and Spiegelman BM. Molecular regulation of adipogenesis. Annual Review of Cell and Developmental Biology, 2000; 16:145-171. 6. Rosen ED, Puigserver P, Walkey CJ, Spiegelman BM. Transcriptional control of adipogenesis. Genes and Development, 2000; 14: 1293-1307. 7. Rosen ED and Spiegelman BM. Peroxisome-proliferator-activated receptor gamma ligands and atherosclerosis: ending the heartache. Journal of Clinical Investigation, 2000; 106: 629-631. 8. Rosen ED, Spiegelman BM. PPARgamma: A nuclear regulator of metabolism, differentiation, and cell growth. J Biol Chem. 2001; 276: 37731-4. 9. Rosen ED, Hsu CH, Wang X, Sakai S, Freeman MW, Gonzalez FJ, Spiegelman BM. C/EBPalpha induces adipogenesis through PPARgamma: a unified pathway.Genes Dev. 2002;16:22-6. 10. Rosen ED. The molecular control of adipogenesis, with special reference to lymphatic pathology. Ann N Y Acad Sci. 2002;979:143-58; discussion 188-96. 11. Rosen ED, Kulkarni RN, Sarraf P, Ozcan U, Okada T, Hsu CH, Eisenman D, Magnuson MA, Gonzalez FJ, Kahn CR, Spiegelman BM. Targeted elimination of peroxisome proliferator-activated receptor gamma in beta cells leads to abnormalities in islet mass without compromising glucose homeostasis. Mol Cell Biol. 2003;23:7222-9.