Aire-expressing thymic medullary epithelial cells originate from β5t-expressing progenitor cells

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 24; pp. 9885 - 9890
• Main Authors: Ohigashi, Izumi, Zuklys, Saulius, Sakata, Mie, Mayer, Carlos E., Zhanybekova, Saule, Murata, Shigeo, Tanaka, Keiji, Holländer, Georg A., Takahama, Yousuke
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 11.06.2013; National Acad Sciences
• Subjects: AIRE Protein; Animals; Biological Sciences; Cells; Developmental biology; Epithelial cells; Epithelial Cells - metabolism; Flow Cytometry; Fluorescence; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; Integrases - genetics; Integrases - metabolism; Male; Messenger RNA; Mice; Mice, 129 Strain; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Microscopy, Confocal; Progenitor cells; Proteasome Endopeptidase Complex - genetics; Proteasome Endopeptidase Complex - metabolism; Stem cells; Stem Cells - metabolism; T lymphocytes; T-Lymphocytes - metabolism; Thymocytes; Thymus Gland - cytology; Thymus Gland - embryology; Thymus Gland - metabolism; Time Factors; Transcription Factors - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1301799110

The thymus provides multiple microenvironments that are essential for the development and repertoire selection of T lymphocytes. The thymic cortex induces the generation and positive selection of T lymphocytes, whereas the thymic medulla establishes self-tolerance among the positively selected T lymphocytes. Cortical thymic epithelial cells (cTECs) and medullary TECs (mTECs) constitute the major stromal cells that structurally form and functionally characterize the cortex and the medulla, respectively. cTECs and mTECs are both derived from the endodermal epithelium of the third pharyngeal pouch. However, the molecular and cellular characteristics of the progenitor cells for the distinct TEC lineages are unclear. Here we report the preparation and characterization of mice that express the recombinase Cre instead of β5t, a proteasome subunit that is abundant in cTECs and not detected in other cell types, including mTECs. By crossing β5t-Cre knock-in mice with loxP-dependent GFP reporter mice, we found that β5t-Cre–mediated recombination occurs specifically in TECs but not in any other cell types in the mouse. Surprisingly, in addition to cTECs, β5t-Cre-loxP–mediated GFP expression was detected in almost all mTECs. These results indicate that the majority of mTECs, including autoimmune regulator-expressing mTECs, are derived from β5t-expressing progenitor cells.