Massachusetts General Hospital

Group Members

Fellows
Toshimi Yoshida, PhD, Instructor in Dermatology
Taku Naito, PhD, Instructor in Dermatology
John Seavitt, PhD, Research Fellow
Mariko Kashiwagi, PhD, Research Fellow
Idit Hazan, PhD, Research Fellow
Ila Joshi, PhD, Research Fellow
 
Student
Samuel Ng, Graduate Student, Program in Immunology HMS
 
Research Assistant
Robert Czyzewski
 
Collaborators
Jiangwen Zhang, PhD, Senior Computational Biologist FAS Center for Systems Biology, Harvard University
Bruce Morgan, PhD, Associate Professor of Dermatology, CBRC

Research Projects

In many developmental systems, nuclear regulators have been implicated in coupling key events in gene expression with specific cell fate and lineage decisions. Focusing on this topic in the hemo-lymphoid system, we have identified the Ikaros gene family of zinc finger DNA binding proteins and shown in a series of genetic studies that they function as key regulators of lymphocyte specification working from the level of the hemopoietic stem cell (HSC). These fundamental studies continue to contribute insight into the earliest steps of the B and T cell differentiation pathways and the molecular network that supports cell fate decisions in the hemo-lymphoid system.

The molecular mechanisms by which Ikaros and its family members exert their range of effects in the hemo-lymphoid system have been under investigation using molecular and biochemical approaches. Importantly, purification of Ikaros and its family member Aiolos from both resting and activated lymphocytes has shown that they exist as part of two functionally distinct chromatin remodeling machineries; an Ikaros-NURD complex, which contains the DNA-dependent ATPase Mi-2 and histone deacetylases, and an Ikaros-SWI/SNF complex which contains the DNA-dependent ATPase Brg-1. Essentially all of the Ikaros found in lymphocytes is in these two higher order molecular entities. This provides an unprecedented example of a factor with demonstrated function as an essential regulator of mammalian development that acts possibly by guiding functionally distinct chromatin remodeling machineries. This combination of attributes makes Ikaros an ideal entry point to study epigenetics in stem cell commitment and differentiation. Our current work focuses on the ability of Ikaros proteins to partition in these functionally distinct higher order molecular complexes and the way that these distinct complexes alter chromatin structure and expression of lineage-specific genes. The genetic interactions between Ikaros and its chromatin remodeling associates are being explored in a series of conditional inactivation studies in mice. These studies are providing evidence of a regulatory network that is comprised of positive and negative regulatory factors whose intimate interactions are responsible for developmental decisions and homeostasis in the hemopoietic system.

Studies on Ikaros gene regulation continue to target our original goal of determining the combination of transcriptional inputs required for induction of a HSC gene expression program. Ikaros regulatory elements coupled with genes encoding fluorescent markers are proving invaluable for the effective separation of rare stem cell and precursor activities and are allowing an in vivo real time analysis of their development. Achieving these goals will dramatically increase the ability to analyze and manipulate development of the HSC in vitro with potential therapeutic implications.

Areas of research:

1. Ontogeny of the hemo-lymphoid system.
Critical insight into the regulation of the early steps of the hemo-lymphoid pathways was obtained by studying mice with Ikaros mutations.  Ikaros expressed in the HSC is required for the production and maintenance but also the differentiation of HSC into the lymphoid pathways. Studies on the hemo-lymphoid hierarchy in the Ikaros mutant mice have identified gene targets responsible for some of the cellular defects and have generated a platform on which to study the molecular mechanisms employed by these factors. Studies on Ikaros regulatory elements, which are active in the HSC and progenitor compartments, are also providing us with powerful molecular tools to study transcriptional regulation at the very first steps in the hemopoietic pathway. These Ikaros regulation studies have increased our ability to manipulate gene expression in the early hemo-lymphoid populations and further dissect the HSC compartment and lymphoid progenitors and precursors. (Select publications: 1, 2, 8, 10)

2. Immune response/lymphocyte function.
Studies on the mature T and B cell populations in mice with deficits in Ikaros, Aiolos and more recently in their associate Mi-2 have identified a nuclear network that controls a lymphocyte's response to stimulation and its subsequent maturation to an effector state. Studies on Aiolos deficient mice in particular have provided us with some of the mechanisms that control the fate of naive mature B cell upon antigenic encounter. Importantly, the decision of a naive B cell to assume a marginal zone or a follicular B cell fate, a B cell's ability to enter a Germinal Center (GC) reaction, as well as selection of GC B cells for high antigen specificity are all processes that are dependent on Aiolos. Furthermore, the high affinity long-lived plasma cell population that resides in the bone marrow and is responsible for long-term humoral immunity but not other plasma cells requires Aiolos for its generation. (Select publications: 5, 6, 12, 13)

3. Lymphoid cancers.
Proliferative responses in T and B cells depend on levels of the DNA binding isoforms of Ikaros and Aiolos or their activity.  Progressive reduction in Ikaros and Aiolos DNA binding factors in respective T and B cell populations results in a progressive increase in proliferative responses and cause rapid neoplastic transformations. (Select publications 3, 5, 6, 12)

4. Chromatin regulation of hemo-lymphopoiesis.
The Ikaros family proteins represent an important group of developmental regulators.  Their association with chromatin remodeling machineries (NURD and SWI/SNF) has provided evidence for a critical role of chromatin regulation in lineage-specification. Studies on the CD8 gene have provided us insight on how Ikaros promotes accessibility at the CD8 enhancers and allows for activation of these enhancers during T cell development. The wealth of markers for lineage progression, and the ability to analyze this process in mouse mutants and in vitro, make the hemo-lymphoid system an ideal model to study the role of directed chromatin remodeling in lineage progression. The Ikaros family and its associates are uniquely suited representatives for these studies. The insights gained by studying Ikaros and its associates, their gene targets and effects on chromatin structure serve as a paradigm for research in this field.  They also provide us with the ability to study how hemopoiesis and the immune response are regulated at this molecular level. (Select publications: 7, 9 and 13)

5. Development of complex epithelia.
Development, morphogenesis and self-renewal of skin appendages share some intriguing parallels to hemopoiesis. The accessibility, and self-renewal features, coupled with its highly organized and fascinating architecture, make the skin an attractive system for exploring the molecular mechanisms that underlie stem cell properties as well as complex differentiation programs. The Ikaros homologues Helios and Dedalos and their associated chromatin remodelers are highly expressed in the developing epithelia of the skin. We are now utilizing epithelial-specific conditional inactivation and biochemical approaches to address the role of these factors during skin development and morphogenesis.  We hope that our past expertise on the hemopoietic system combined with the local expertise on skin differentiation will in the near future provide a breakthrough in the mechanisms that control epithelial development.

Transgenic and Gene Targeting Facility

nt breakthroughs in lineage transcriptional priming

Table.1 Lineage-specific signatures deduced by K-mean clustering (Ng. et. al., Immunity 2009; 30: 1-15)

Publications:

1. Zhang J, Jackson AF, Naito T, Dose M, Seavitt J, Liu F, Heller EJ, Kashiwagi M, Yoshida T, Gounari F, Petrie HT, Georgopoulos K. Harnessing of the nuclesome-remodeling-deacetylase complex controls lymphocyte development and prevents leukemogenesis. Nat Immunol. 2011 13(1): 86-94.
2. Gomez-del Arco P, Kashiwagi M, Jackson AF, Naito T, Zhang J, Liu F, Kee B, Vooijs M, Radtke F, Redono JM, Georgopoulos K. Alternative promoter usage at the Notch 1 locus supports ligand-independent signaling in T cell development and leukemogenesis. Immunity. 2010 33(5): 685-98
3. Yoshida T, Ng SY, Georgopoulos K. Awakening lineage potential by Ikaros-mediated transcriptional priming.  Curr Opin Immunol. 2010 22(2): 154-60.
4. Ng, SY, Yoshida, T, Zhang, J. and Georgopoulos, K. Genome-wide lineage-specific transcriptional programs underscore Ikaros-dependent lymphoid priming in multi-potent hematopoietic stem cells. Immunity 2009 30(4): 493-507.
5. Georgopoulos K. Acute lymphoblastic leukemia--on the wings of IKAROS. N Engl J Med. 2009 29;360(5):524-6.
6. Georgopoulos K. From immunity to tolerance through HDAC. Nat Immunol. 2009;10(1):13-4.
7. Yoshida T, Hazan I, Zhang J, Ng SY, Naito T, Snippert HJ, Heller EJ, Qi X, Lawton LN, Williams CJ, Georgopoulos K. The role of the chromatin remodeler Mi-2beta in hematopoietic stem cell self-renewal and multilineage differentiation. Genes Dev. 2008 1;22(9):1174-89.
8. Naito T, Gómez-Del Arco P, Williams CJ, Georgopoulos K. Antagonistic interactions between Ikaros and the chromatin remodeler Mi-2beta determine silencer activity and Cd4 gene expression. Immunity. 2007 27(5):723-34.
9. Georgopoulos K, Kioussis D. Epigenetic flexibility underlying lineage choices in the adaptive immune system. Science. 2007 3;317(5838):620-2.
10. Agoston DV, Szemes M, Dobi A, Palkovits M, Georgopoulos K, Gyorgy A, Ring MA. Ikaros is expressed in developing striatal neurons and involved in enkephalinergic differentiation. J Neurochem. 2007 PMID: 17504264 102(6):1805-16.
11. Thompson EC, Cobb BS, Sabbattini P, Meixlsperger S, Parelho V, Liberg D, Taylor B, Dillon N, Georgopoulos K, Jumaa H, Smale ST, Fisher AG, Merkenschlager M. Ikaros DNA-binding proteins as integral components of B cell developmental-stage-specific regulatory circuitsImmunity. 2007 26(3):335-44. PMID: 17363301
12. Kashiwagi M, Morgan BA, Georgopoulos K.The chromatin remodeler Mi-2beta is required for establishment of the basal epidermis and normal differentiation of its progeny. Development. 2007 134(8):1571-82. PMID: 17360773
13. Yoshida T, Ng SY, Zuniga-Pflucker JC, Georgopoulos K Early hematopoietic lineage restrictions directed by Ikaros. Nat Immunol. 2006(4):382-91.PMID: 16518393
14. Ueda Y, Okano M, Williams C, Chen T, Georgopoulos K, Li E Roles for Dnmt3b in mammalian development: a mouse model for the ICF syndrome.Development. 2006 133(6):1183-92.
15. Liu E, Sinha S, Williams C, Cyrille M, Heller E, Snapper SB, Georgopoulos K, St-Arnaud R, Force T, Dedhar S, Gerszten RE.Targeted deletion of integrin-linked kinase reveals a role in T-cell chemotaxis and survival.Mol Cell Biol. 2005 Dec;25(24):11145-55. PMID: 16314534
16. Gómez-del Arco P, Koipally J, Georgopoulos K. Ikaros SUMOylation: switching out of repression. Mol Cell Biol. 2005 25(7):2688-97.PMID: 15767674]
17. Williams CJ, Naito T, Arco PG, Seavitt JR, Cashman SM, De Souza B, Qi X, Keables P, Von Andrian UH, Georgopoulos K.The chromatin remodeler Mi-2beta is required for CD4 expression and T cell development. Immunity. 2004 20(6):719-33.PMID: 15189737
18. Gómez-del Arco P, Maki K, Georgopoulos K.Phosphorylation controls Ikaros's ability to negatively regulate the G(1)-S transition.Mol Cell Biol. 2004 24(7):2797-807. PMID: 15024069
19. Cortés M, Georgopoulos K Aiolos is required for the generation of high affinity bone marrow plasma cells responsible for long-term immunity. J Exp Med. 2004 19;199(2):209-19.PMID: 14718515
20. Kaufmann C, Yoshida T, Perotti EA, Landhuis E, Wu P, Georgopoulos K. A complex network of regulatory elements in Ikaros and their activity during hemo-lymphopoiesis. EMBO J. 2003 May 1;22(9):2211-23.PMID: 12727887
21. Sun J, Matthias G, Mihatsch MJ, Georgopoulos K, Matthias P.Lack of the transcriptional coactivator OBF-1 prevents the development of systemic lupus erythematosus-like phenotypes in Aiolos mutant mice.J Immunol. 2003 15;170(4):1699-706.PMID: 12574333
22. Harker N, Naito T, Cortes M, Hostert A, Hirschberg S, Tolaini M, Roderick K, Georgopoulos K, Kioussis D.The CD8alpha gene locus is regulated by the Ikaros family of proteins.Mol Cell. 2002 Dec;10(6):1403-15. PMID: 12504015
23. Koipally J, Georgopoulos K A molecular dissection of the repression circuitry of Ikaros. J Biol Chem. 2002 2;277(31):27697-705. PMID: 12015313
24. Koipally J, Georgopoulos K.Ikaros-CtIP interactions do not require C-terminal binding protein and participate in a deacetylase-independent mode of repression. J Biol Chem. 2002 28;277(26):23143-9. PMID: 11959865
25. Georgopoulos K. Haematopoietic cell-fate decisions, chromatin regulation and ikaros. Nat Rev Immunol. 2002 2(3):162-74PMID: 11913067
26. Koipally J, Heller EJ, Seavitt JR, Georgopoulos K.Unconventional potentiation of gene expression by Ikaros.J Biol Chem. 2002 12;277(15):13007-15. Epub 2002 Jan 17.
27. DiFronzo NL, Leung CT, Mammel MK, Georgopoulos K, Taylor BJ, Pham QN. Ikaros, a lymphoid-cell-specific transcription factor, contributes to the leukemogenic phenotype of a mink cell focus-inducing murine leukemia virus. J Virol. 2002 Jan;76(1):78-87.
28. Georgopoulos K.Haematopoietic cell-fate decisions, chromatin regulation and ikaros. Nat Rev Immunol. 2002 2(3):162-74. PMID: 11913067
29. Cariappa A, Tang M, Parng C, Nebelitskiy E, Carroll M, Georgopoulos K, Pillai S.The follicular versus marginal zone B lymphocyte cell fate decision is regulated by Aiolos, Btk, and CD21.Immunity. 2001,14(5):603-15.PMID: 11371362
30. Wu L, Vandenabeele S, Georgopoulos K. Int Rev Immunol. 2001; 20(1):117-35. PMID: 11342301
31. Yamada A, Takaki S, Hayashi F, Georgopoulos K, Perlmutter RM, Takatsu K. Identification and characterization of a transcriptional regulator for the lck proximal promoter. J Biol Chem. 2001 25;276(21):18082-9PMID: 11278409
32. Koipally J, Georgopoulos K.Ikaros interactions with CtBP reveal a repression mechanism that is independent of histone deacetylase activity.J Biol Chem. 2000 30;275(26):19594-602. PMID:10766745
33. Galy A, Christopherson I, Ferlazzo G, Liu G, Spits H, Georgopoulos K.Distinct signals control the hematopoiesis of lymphoid-related dendritic cells. Blood. 2000 1;95(1):128-37. PMID: 10607695
34. Nichogiannopoulou A, Trevisan M, Neben S, Friedrich C, Georgopoulos K.Defects in hemopoietic stem cell activity in Ikaros mutant mice.J Exp Med. 1999 1;190(9):1201-14.PMID:
35. Winandy S, Wu L, Wang JH, Georgopoulos K.Pre-T cell receptor (TCR) and TCR-controlled checkpoints in T cell differentiation are set by Ikaros. J Exp Med. 1999 18;190(8):1039-48.PMID: 10523602
36. Georgopoulos K.Gene regulation and cancer. AACR meeting review, the Homestead, Hot Springs, VA, USA, 14-18 October 1998. Biochim Biophys Acta. 1999 31;1423(3):R75-9. PMID: 10382542
37. Koipally J, Renold A, Kim J, Georgopoulos K.Repression by Ikaros and Aiolos is mediated through histone deacetylase complexes. EMBO J. 1999 1;18(11):3090-100.PMID: 10357820
38. Cortes M, Wong E, Koipally J, Georgopoulos K.Control of lymphocyte development by the Ikaros gene family.Curr Opin Immunol. 1999 Apr;11(2):167-71PMID: 10322160
39. Kim J, Sif S, Jones B, Jackson A, Koipally J, Heller E, Winandy S, Viel A, Sawyer A, Ikeda T, Kingston R, Georgopoulos K.Ikaros DNA-binding proteins direct formation of chromatin remodeling complexes in lymphocytes. Immunity. 1999 ;10(3):345-55.PMID: 10204490
40. Avitahl N, Winandy S, Friedrich C, Jones B, Ge Y, Georgopoulos K. Ikaros sets thresholds for T cell activation and regulates chromosome propagation. Immunity. 1999 ;10(3):333-43. PMID: 10204489
41. Koipally J, Kim J, Jones B, Jackson A, Avitahl N, Winandy S, Trevisan M, Nichogiannopoulou A, Kelley C, Georgopoulos K. Ikaros chromatin remodeling complexes in the control of differentiation of the hemo-lymphoid system.Cold Spring Harb Symp Quant Biol. 1999;64:79-86 PMID: 11232340
42. Shortman K, Vremec D, Corcoran LM, Georgopoulos K, Lucas K, Wu L.The linkage between T-cell and dendritic cell development in the mouse thymus. Immunol Rev. 1998;165:39-46 PMID:
43. Wang JH, Avitahl N, Cariappa A, Friedrich C, Ikeda T, Renold A, Andrikopoulos K, Liang L, Pillai S, Morgan BA, Georgopoulos K. Aiolos regulates B cell activation and maturation to effector state. Immunity. 1998;9(4):543-53. PMID: 9806640
44. Georgopoulos K.Introduction. Semin Immunol. 1998;10(2):101-2. No abstract available. PMID: 9653041 https://phstwlp1.partners.org:2443/login?url=http://www.ncbi.nlm.nih.gov/pubmed
45. Nichogiannopoulou A, Trevisan M, Friedrich C, Georgopoulos K. Ikaros in hemopoietic lineage determination and homeostasis. Semin Immunol. 1998;10(2):119-25. Review. PMID: 9618757
46. Kelley CM, Ikeda T, Koipally J, Avitahl N, Wu L, Georgopoulos K, Morgan BA. Helios, a novel dimerization partner of Ikaros expressed in the earliest hematopoietic progenitors.Curr Biol. 1998; 8(9):508-15. PMID: 9560339
47. Wu L, Nichogiannopoulou A, Shortman K, Georgopoulos K. Cell-autonomous defects in dendritic cell populations of Ikaros mutant mice point to a developmental relationship with the lymphoid lineage. Immunity. 1997;7(4):483-92. PMID: 9354469
48. Morgan B, Sun L, Avitahl N, Andrikopoulos K, Ikeda T, Gonzales E, Wu P, Neben S, Georgopoulos K.Aiolos, a lymphoid restricted transcription factor that interacts with Ikaros to regulate lymphocyte differentiation.EMBO J. 1997;16(8):2004-13. PMID: 9155026
49. Georgopoulos K.Transcription factors required for lymphoid lineage commitment. Curr Opin Immunol. 1997;9(2):222-7. Review.PMID: 9099800
50. Georgopoulos K, Winandy S, Avitahl N.The role of the Ikaros gene in lymphocyte development and homeostasis. Annu Rev Immunol. 1997;15:155-76. Review. PMID: 9143685
51. Wang JH, Nichogiannopoulou A, Wu L, Sun L, Sharpe AH, Bigby M, Georgopoulos K.Selective defects in the development of the fetal and adult lymphoid system in mice with an Ikaros null mutation. Immunity. 1996 5(6):537-49.PMID: 8986714 : http://phstwlp1.partners.org:2111/pubmed/8986714?ordinalpos=47&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum
52. Sun L, Liu A, Georgopoulos K.Zinc finger-mediated protein interactions modulate Ikaros activity, a molecular control of lymphocyte development.EMBO J. 1996 1;15(19):5358-69.PMID: 8895580
53. Molnár A, Wu P, Largespada DA, Vortkamp A, Scherer S, Copeland NG, Jenkins NA, Bruns G, Georgopoulos K.The Ikaros gene encodes a family of lymphocyte-restricted zinc finger DNA binding proteins, highly conserved in human and mouse.J Immunol. 1996 15;156(2):585-92.PMID: 8543809
54. Winandy S, Wu P, Georgopoulos A dominant mutation in the Ikaros gene leads to rapid development of leukemia and lymphoma.Cell. 1995 20;83(2):289-99.PMID: 7585946 http://phstwlp1.partners.org:2111/pubmed/7585946?ordinalpos=52&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum
55. Molnár A, Georgopoulos K.The Ikaros gene encodes a family of functionally diverse zinc finger DNA-binding proteins.Mol Cell Biol. 1994 Dec;14(12):8292-303. PMID: 7969165
56. Georgopoulos K, Bigby M, Wang JH, Molnar A, Wu P, Winandy S, Sharpe A.The Ikaros gene is required for the development of all lymphoid lineages.Cell. 1994 7;79(1):143-56.PMID: 7923373
57. Clevers HC, Oosterwegel MA, Georgopoulos K.Transcription factors in early T-cell development. Immunol Today. 1993;14(12):591-6. Review.PMID: 7905739
58. Georgopoulos K, Moore DD, Derfler B. Ikaros, an early lymphoid-specific transcription factor and a putative mediator for T cell commitment.Science. 1992 Oct 30;258(5083):808-12.PMID: 1439790
59. Georgopoulos K, Morgan BA, Moore DD.Functionally distinct isoforms of the CRE-BP DNA-binding protein mediate activity of a T-cell-specific enhancer.Mol Cell Biol. 1992;12(2):747-57.PMID: 1531087
60. Oosterwegel M, van de Wetering M, Dooijes D, Klomp L, Winoto A, Georgopoulos K, Meijlink F, Clevers H. Cloning of murine TCF-1, a T cell-specific transcription factor interacting with functional motifs in the CD3-epsilon and T cell receptor alpha enhancers.J Exp Med. 1991 1;173(5):1133-42.PMID: 1827138
61. Georgopoulos K, Galson D, Terhorst C.Tissue-specific nuclear factors mediate expression of the CD3 delta gene during T cell development.EMBO J. 1990;9(1):109-15.PMID: 2136828
62. Wilkinson MF, Georgopoulos K, Terhorst C, MacLeod CL.The CD3 delta gene encodes multiple transcripts regulated by transcriptional and post-transcriptional mechanisms. Eur J Immunol. 1989;19(12):2355-60.PMID: 2532602