Transgenic TSCOT promoter is Active in Precursor and the Compartmentalized Thymic Epithelial Cells

초록

TSCOT was originally found as an unique gene exclusively expressed in the cortical thymic epithelial cells. Using histology and flow cytometry with TSCOT promoter driven cre transgenic mouse systems, we investigated the processes of development and lineage specification of thymic epithelial cells. In contrast to the endogenous cortical TSCOT expression, 3.1Kb promoter showed activity in the medulla of the adult transgenic thymus. When Cre transgenic mouse lines under the control of 3.1 or 4.4kb TSCOT promoter were crossed with ROSA reporters, expressions were found exclusively in the thymus, but not in any other organs in fetal and neonate stages. LacZ and EGFP reporter expression was found in both cortex and medulla, indicating Cre activity turned on in early thymic epithelial development before lineage specification occurs. The subpopulation of precursor thymic epithelial (MHCII high, UEA-1intermediate, CDR1intermediate) expressed EGFP in addition to Keratin 5 and Keratin 8 expression in 2 week thymus. These results suggest the presence of thymic compartment specific regulatory elements in the TSCOT in addition to thymus organ specific element, and promoter is active in the precursor stage before compartment specification during development.