Notch signaling requires GATA-3 for the survival of cells entering the T-lineage development program (64.4)

Abstract GATA-3 plays a crucial role in T cell development, however its role and collaboration with the Notch signaling pathway in the induction of T cell specification and commitment have not been fully elucidated. Work in our laboratory using both, in vitro and in vivo models of T cell development, has shown that GATA-3 deficiency arrests this development at the DN2 stage but does not result in B-lymphopoiesis in the presence of Notch ligand Delta-like 1 (Dll1). These GATA-3-/- progenitors express T-lineage associated genes but are unable to survive the T-specification event as indicated by their increased rate of apoptosis. Cell cycle regulation genes, mainly p19Arf and p16Ink4a (Arf/Ink), are upregulated in these cells as indicated by gene expression microarray and qRT-PCR analyses. We have thus sought to address the possibility that GATA-3 represses Arf/Ink following T cell specification/commitment in the presence of Notch signals. We are employing ChIP assay to show whether potential GATA-3 recognition sequences present in the Arf/Ink promoter region are occupied and regulated by GATA-3. Finally, using GATA-3-/-Arf-Ink-/- bone marrow progenitors, we will address a possible rescue of the early T cell developmental block observed in the absence of GATA-3. These experiments will help to identify a potential mechanism of how GATA-3 and the Notch signaling pathway collaborate in regulating T-lineage specification, commitment and survival during T cell development.