Naomi Goldman (Mentor: Golnaz Vahedi, PhD)

“Exploring the mechanisms that establish the chromatin state of T cells”

Naomi Goldman, Aditi Chandra, Maria Fasolino and Golnaz Vahedi

Cell fate-specific gene expression programs are established in part by alterations in chromatin accessibility via the action of lineage-determining transcription factors (TFs). Work in our lab has identified that the transcription factor TCF-1—integral for normal thymic development—targets and is essential for the opening of repressed chromatin in T cells1. In other cell-types, LDTFs are known to collaborate to organize a fully active enhancer2,3. However, the mechanism through which TCF-1 acts at enhancers in order to regulate genes during T cell development is unknown. To characterize the role of TCF-1 in the establishment of the T cell epigenome, I immunoprecipitated TCF-1 in thymocytes followed by a mass spectrometry (MS) analysis to identify interacting proteins. The proteins that were enriched in the TCF-1 IP relative to a IgG pull down included multiple subunits of the SWI/SNF chromatin remodeling complex. Previous work has shown that exogenous expression of TCF-1 in NIH3T3 fibroblasts leads to a gain in chromatin accessibility at T cell regulatory regions and appears to be dependent on SWI/SNF. To further assess interactions between TCF-1 and other proteins I created multiple mutant TCF-1 constructs by deleting domains spanning the protein. Utilizing these mutants, I am testing the role of various TCF-1 protein domains on chromatin accessibility and gene expression in a developmental T cell line as well as in primary developing T cells utilizing an OP9-DL1 co-culture system. These studies aim to provide mechanistic insight into how transcription factors work to establish cell identity in addition to adding to our understanding of how cell fate might be reprogramed at will for therapeutic purposes will be recognized.