Mitchell A. Lazar, M.D., Ph.D.

Discovery of Rev-erba and mechanism of repression by nuclear receptors. I discovered receptors for thyroid hormone as well as the orphan NR that we named Rev-erba that is the subject of this proposal. My lab demonstrated that Rev-erbs bind to a unique DNA sequence as a monomer and to a related site as a dimer. We were among the first to recognize that NRs have a ligand-independent repression function, and we discovered the CoRNR box motif which explains why corepressors bind to unliganded but not liganded forms of nuclear receptors. Most recently we discovered that Rev-erba represses transcription at the genome both directly and indirectly, i.e., independent of its DNA-binding domain. Together, our studies have demonstrated the mechanism and physiological significance of repression by Rev-erba and other NRs.

• Lazar MA, Hodin RA, Darling DS, Chin WW. A novel member of the thyroid/steroid hormone receptor family is encoded by the opposite strand of the rat c-erbA alpha transcriptional unit. Mol Cell Biol. 1989 Mar;9(3):1128-36. PubMed PMID: 2542765; PubMed Central PMCID: PMC362703.
• Harding HP, Lazar MA. The monomer-binding orphan receptor Rev-Erb represses transcription as a dimer on a novel direct repeat. Mol Cell Biol. 1995 Sep;15(9):4791-802. Erratum in: Mol Cell Biol 1995 Nov;15(11):6479. PubMed PMID: 7651396; PubMed Central PMCID: PMC230723.
• Hu X, Lazar MA. The CoRNR motif controls the recruitment of corepressors by nuclear hormone receptors. Nature. 1999 Nov 4;402(6757):93-6. PubMed PMID:10573424.
• Zhang Y, Fang B, Emmett MJ, Damle M, Sun Z, Feng D, Armour SM, Remsberg JR, Jager J, Soccio RE, Steger DJ, Lazar MA. Discrete functions of nuclear receptor Rev-erba couple metabolism to the clock. Science 348:1488-1492, 2015. PubMed PMID: 26044300; PubMed Central PMCID: PMC4613749.

Nuclear Receptor Corepressor Complexes. My laboratory was first to purify an endogenous NR corepressor complex, and discovered the stoichiometric presence of the epigenome modifying enzyme HDAC3. We demonstrated that HDAC3 polypeptide itself has little intrinsic enzymatic activity, and its deacetylation function requires interaction with a region of NCoR or SMRT that we termed the DAD (“Deacetylase Activating Domain”), and that the catalytic activity of HDAC3 requires the DAD in vivo. We also generated NCoR mutant mice to show for the first time that corepressors and HDAC3 were critical for normal adult physiology. These studies have demonstrated the repression mechanisms and physiological functions of nuclear receptor corepressors.

• Guenther MG, Lane WS, Fischle W, Verdin E, Lazar MA (corresponding), Shiekhattar R. A core SMRT corepressor complex containing HDAC3 and TBL1, a WD40-repeat protein linked to deafness. Genes Dev. 2000 May 1;14(9):1048 57. PubMed PMID: 10809664; PubMed Central PMCID: PMC316569.
• Guenther MG, Barak O, Lazar MA. The SMRT and N-CoR corepressors are activating cofactors for histone deacetylase 3. Mol Cell Biol. 2001 Sep;21(18):6091-101. PubMed PMID: 11509652; PubMed Central PMCID: PMC87326.
• Alenghat T, Meyers K, Mullican SE, Leitner K, Adeniji-Adele A, Avila J, Buƒáan M, Ahima RS, Kaestner KH, Lazar MA. Nuclear receptor corepressor and histone deacetylase 3 govern circadian metabolic physiology. Nature. 2008 Dec 18;456(7224):997-1000. doi: 10.1038/nature07541. Epub 2008 Nov 26. PubMed PMID: 19037247; PubMed Central PMCID: PMC2742159.
•  You SH, Lim HW, Sun Z, Broache M, Won KJ, Lazar MA. Nuclear receptor co-repressors are required for the histone-deacetylase activity of HDAC3 in vivo. Nat Struct Mol Biol. 2013 Feb;20(2):182-7. doi: 10.1038/nsmb.2476. Epub 2013 Jan 6. PubMed PMID: 23292142; PubMed Central PMCID: PMC3565028.

PPARg in Adipose Biology. In 1994, we reported that PPARg is predominantly expressed in adipose tissue and induced during adipocyte differentiation. We found that phosphorylation regulates PPARg activity and in vivo insulin sensitivity, and that adipose PPARg is required for normal fat development in vivo. We were first to characterize the PPARg cistrome in mouse adipocytes, and demonstrate a role for nearby binding of C/EBPa. We have also shown that antidiabetic TZD ligands activate PPARg bound at enhancers, while transrepression is due redistribution of coactivators away from enhancer sites controlled by other factors. Most recently we demonstrated that SNPs regulate adipose tissue PPARg binding, function, and response to TZDs. In sum, we identified PPARg as an important transcription factor in adipocytes, and have uncovered its mechanisms of action at the genome.

• Chawla A, Schwarz EJ, Dimaculangan DD, Lazar MA. Peroxisome proliferator-activated receptor (PPAR) gamma: adipose-predominant expression and induction early in adipocyte differentiation. Endocrinology. 1994 Aug;135(2):798-800. PubMed PMID: 8033830.
• Lefterova MI, Zhang Y, Steger DJ, Schupp M, Schug J, Cristancho A, Feng D, Zhuo D, Stoeckert CJ Jr, Liu XS, Lazar MA. PPARgamma and C/EBP factors orchestrate adipocyte biology via adjacent binding on a genome-wide scale. Genes Dev. 2008 Nov 1;22(21):2941-52. doi: 10.1101/gad.1709008. PubMed PMID: 18981473; PubMed Central PMCID: PMC2577797.
• Step SE, Lim HW, Marinis JM, Prokesch A, Steger DJ, You SH, Won KJ, Lazar MA. Anti-diabetic rosiglitazone remodels the adipocyte transcriptome by redistributing transcription to PPARg-driven enhancers. Genes Dev. 2014 May 1;28(9):1018-28. doi: 10.1101/gad.237628.114. PubMed PMID: 24788520; PubMed Central PMCID: PMC4018489.
• Soccio RE, Chen ER, Rajapurkar SR, Safabakhsh P, Steger DJ, Marinis JM, Dispirito JR, Briggs ER, Fang B, Everett LJ, Lim HW, Won KJ, Wu Y, Civelek M, Voight BF, Lazar MA. Genetic variation determines PPARg function and antidiabetic drug response in vivo. Cell 162:33-44, 2015. PMCID: PMC4493773 [Available on 2016-07-02].

Resistin. In 2001, we discovered the polypeptide hormone resistin as an adipocyte-specific, secreted protein whose gene expression was down-regulated by TZD treatment. We also discovered a family of other Resistin-Like Molecules (RELMs). We showed ectopic resistin exacerbated insulin resistance while genetic deletion of resistin improved glucose metabolism. We found that resistin expression in adipocytes requires a PPARg binding site that is present in the mouse genome but absent in humans (e), where resistin is secreted mainly from monocytes in response to inflammatory stimuli. Humanizing mice for resistin exacerbated insulin resistance due to inflammation. In sum, our discovery of resistin and its role in insulin resistance have contributed in a major way to current understanding of how adipokines and inflammation impact metabolism.

• Steppan CM, Bailey ST, Bhat S, Brown EJ, Banerjee RR, Wright CM, Patel HR, Ahima RS, Lazar MA. The hormone resistin links obesity to diabetes. Nature. 2001 Jan 18;409(6818):307-12. PubMed PMID: 11201732.
• Steppan CM, Brown EJ, Wright CM, Bhat S, Banerjee RR, Dai CY, Enders GH, Silberg DG, Wen X, Wu GD, Lazar MA. A family of tissue-specific resistin-like molecules. Proc Natl Acad Sci U S A. 2001 Jan 16;98(2):502-6. PubMed PMID:11209052; PubMed Central PMCID: PMC14616.
• Banerjee RR, Rangwala SM, Shapiro JS, Rich AS, Rhoades B, Qi Y, Wang J, Rajala MW, Pocai A, Scherer PE, Steppan CM, Ahima RS, Obici S, Rossetti L, Lazar MA. Regulation of fasted blood glucose by resistin. Science. 2004 Feb 20;303(5661):1195-8. PubMed PMID: 14976316.
• Qatanani M, Szwergold NR, Greaves DR, Ahima RS, Lazar MA. Macrophage-derived human resistin exacerbates adipose tissue inflammation and insulin resistance in mice. J Clin Invest. 2009 Mar;119(3):531-9. doi: 10.1172/JCI37273. Epub 2009 Feb 2. PubMed PMID: 19188682; PubMed Central PMCID: PMC2648673.

Transcriptional Regulation of Circadian Rhythms and Metabolism. Rev-erba is expressed with a large amplitude circadian rhythm in most cells and represses the activating clock gene BMAL1 via NCoR/HDAC3. We discovered that Rev-erba protein activity is modulated by heme ligand as well as by proteasomal degradation facilitated by lithium. We demonstrated that Rev-erba binds to the genome rhythmically with NCoR/HDAC3 leading to circadian modulation of the epigenome on a genome-wide scale and that loss of Rev-erbs a and b abolishes circadian rhythms. We also were first to characterize circadian enhancers in liver, and discovered the mechanism whereby Rev-erbs and other factors control multiple distinct phases of circadian gene expression. Genetic loss of the Rev-erbs, NCoR, or HDAC3 leads to massive hepatosteatosis in large part via a non-enzymatic function of HDAC3. We are currently interrogating the enzyme-independent functions of HDAC3 in liver. In brown adipose tissue, we discovered that Rev-erba controls circadian rhythm of cold tolerance and heat generation. Together, our studies have demonstrated circadian modulation of the epigenome and its relation to metabolism in health and disease.

• Feng D, Liu T, Sun Z, Bugge A, Mullican SE, Alenghat T, Liu XS, Lazar MA. A circadian rhythm orchestrated by histone deacetylase 3 controls hepatic lipid metabolism. Science. 2011 Mar 11;331(6022):1315-9. doi: 10.1126/science.1198125. PubMed PMID: 21393543; PubMed Central PMCID: PMC3389392.
• Bugge A, Feng D, Everett LJ, Briggs ER, Mullican SE, Wang F, Jager J, Lazar MA. Rev-erba and Rev-erbb coordinately protect the circadian clock and normal metabolic function. Genes Dev. 2012 Apr 1;26(7):657-67. doi: 10.1101/gad.186858.112. PubMed PMID: 22474260; PubMed Central PMCID: PMC3323877.
• Gerhart-Hines Z, Feng D, Emmett MJ, Everett LJ, Loro E, Briggs ER, Bugge A, Hou C, Ferrara C, Seale P, Pryma DA, Khurana TS, Lazar MA. The nuclear receptor Rev-erba controls circadian thermogenic plasticity. Nature. 2013 Nov 21;503(7476):410-3. doi: 10.1038/nature12642. Epub 2013 Oct 27. PubMed PMID: 24162845; PubMed Central PMCID: PMC3839416.
• Fang B, Everett LJ, Jager J, Briggs E, Armour SM, Feng D, Roy A, Gerhart-Hines Z, Sun Z, Lazar MA. Circadian enhancers coordinate multiple phases of rhythmic gene transcription in vivo. Cell. 2014 Nov 20;159(5):1140-52. doi:10.1016/j.cell.2014.10.022. PubMed PMID: 25416951; PubMed Central PMCID: PMC4243056.