An understanding of lymphopoietic regulatory mechanisms is essential for the elucidation of aberrant events that result in leukemias, lymphomas, and immunodeficiencies. Ikaros family members, including Ikaros, Aiolos, and Helios, are DNA-binding proteins that are well- established as critical regulators of lymphopoiesis, but their intracellular functions appear to be atypical and remain unknown. Recent results from our laboratory, in collaboration with the laboratory of Amanda Fisher and Matthias Merkenschlager, have established the Ikaros and Helios often localize to foci of centromeric, heterochromatin. In addition, several cellular genes, including the terminal transferase (TdT) gene, become physically repositioned to these foci when heritably down-regulated. These results suggest that repositioning may be critical for the heritable inactivation of transcription, and that Ikaros may play an essential role in this process. The studies proposed here will use the TdT gene as a model system to examine these hypotheses in greater depth. The long-term objectives of the proposed research are to understand: 1. The order of events which occur when an active gene becomes inactivated and repositioned to ceteromeric foci, and 2. The intracellular functions of Ikaros and Helios, with special emphasis on functions relating to down- regulation and repositioning. To accomplish these objectives, the TdT locus will be examined in double-positive (CD4+CD8+) thymocytes and related cell lines as it comes inactivated, and repositioned. Among the properties that will be examined are its histone modification status, methylation status, and chromatin accessibility to nuclease cleavage. Experiments will also be performed to further explore the relevance of an Ikaros binding site within the TdT promoter for down-regulation and repositioning. To elucidate more fully the targeted to centromeric foci, its interaction with histone deacetylase complexes, and its direct interaction with genomic DNA targets. To facilitate the studies of repositioning and of the intracellular functions of Ikaros proteins, genetically altered mouse strains will be created. To determine if the T cell-specific Helios protein plays an important regulatory role, transgenic mice which express Helios ectopically in the B cell lineage will be analyzed To test the relevance of Ikaros for centromeric repositioning, transgenic mice have been created containing reporter genes downstream of multiple Ikaros binding sites. Finally, to examine the relevance of Ikaros for gene inactivation in lymphocytes, mouse strains allowing the conditional disruption of the Ikaros gene are being prepared.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK043726-13
Application #
6607550
Study Section
Allergy and Immunology Study Section (ALY)
Program Officer
Badman, David G
Project Start
1996-08-01
Project End
2005-05-31
Budget Start
2003-08-01
Budget End
2004-05-31
Support Year
13
Fiscal Year
2003
Total Cost
$282,802
Indirect Cost
Name
University of California Los Angeles
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Schjerven, Hilde; Ayongaba, Etapong F; Aghajanirefah, Ali et al. (2017) Genetic analysis of Ikaros target genes and tumor suppressor function in BCR-ABL1+ pre-B ALL. J Exp Med 214:793-814
Arenzana, Teresita L; Schjerven, Hilde; Smale, Stephen T (2015) Regulation of gene expression dynamics during developmental transitions by the Ikaros transcription factor. Genes Dev 29:1801-16
Heller, Jennifer J; Schjerven, Hilde; Li, Shiyang et al. (2014) Restriction of IL-22-producing T cell responses and differential regulation of regulatory T cell compartments by zinc finger transcription factor Ikaros. J Immunol 193:3934-46
Smale, Stephen T (2014) Transcriptional regulation in the immune system: a status report. Trends Immunol 35:190-4
Schjerven, Hilde; McLaughlin, Jami; Arenzana, Teresita L et al. (2013) Selective regulation of lymphopoiesis and leukemogenesis by individual zinc fingers of Ikaros. Nat Immunol 14:1073-83
Xu, Jian; Smale, Stephen T (2012) Designing an enhancer landscape. Cell 151:929-31
Smale, Stephen T (2010) Pioneer factors in embryonic stem cells and differentiation. Curr Opin Genet Dev 20:519-26
Papathanasiou, Peter; Attema, Joanne L; Karsunky, Holger et al. (2009) Evaluation of the long-term reconstituting subset of hematopoietic stem cells with CD150. Stem Cells 27:2498-508
Papathanasiou, Peter; Attema, Joanne L; Karsunky, Holger et al. (2009) Self-renewal of the long-term reconstituting subset of hematopoietic stem cells is regulated by Ikaros. Stem Cells 27:3082-92
Reynaud, Damien; Demarco, Ignacio A; Reddy, Karen L et al. (2008) Regulation of B cell fate commitment and immunoglobulin heavy-chain gene rearrangements by Ikaros. Nat Immunol 9:927-36

Showing the most recent 10 out of 13 publications