T lymphocyte development and differentiation is a multi-step process that begins 
in the thymus and completed in the periphery. Sequential development of 
thymocytes is dependent on T cell receptor (TCR) signaling and an array of 
transcription factors. In this study we show that special AT-rich binding 
protein 1 (SATB1), a T lineage-enriched chromatin organizer and regulator, is 
induced in response to TCR signaling during early thymocyte development. SATB1 
expression profile coincides with T lineage commitment and upregulation of SATB1 
correlates with positive selection of thymocytes. CD4 thymocytes exhibit a 
characteristic bimodal expression pattern that corresponds to immature and 
mature CD4 thymocytes. We also demonstrate that GATA3, the key transcriptional 
regulator of αβ T cells positively regulates SATB1 expression in thymocytes 
suggesting an important role for SATB1 during T cell development.