Expression Analyses revealed Thymic Stromal Co-Tansporter/Slc46A2 is in stem cell populations and is a Putative Tumor Suppressor

초록

By combining flow cytometry and database searches, we extended the expression profiling of TSCOT/Slc46A2/Ly110, that was shown to be expressed in the bipotent precursor and cortical thymic epithelial cells. Genome scale analysis verified that TSCOT is tissue- and cell type- specific in thymus and is also expressed in other epithelial tissues. Coexpression profiling with genes, Foxn1 and Hoxa3, revealed the role of TSCOT during the tissue formation including early thymic organogenesis. TSCOT expression was detected in all thymic epithelial (TEC), but not in the CD31+ endothelial lineage of fetal thymus. In addition, ABC transporter-dependent side population and Sca-1+ of fetal TEC population contain TSCOT-expressing cells, indicating TEC stem cells express TSCOT. TSCOT expression was identified as early as in differentiating embryonic stem cells. TSCOT expression is not under the control of Foxn1 since TSCOT is present in the thymic rudiment of nude mice. By the searches for expression variation, TSCOT is positively associated with GRHL3 and IRF6. Cytokines such as IL1b, IL22 and IL24 are the potential regulators of the TSCOT expression. Surprisingly, we found TSCOT expression in the lung was diminished in the lung cancers suggesting TSCOT may be involved in the suppression of lung tumor development. From these results, a model for TEC differentiation from the stem cells was proposed in the context of multiple epithelial organ formation.