title: Polycomb group gene Bmi1 plays a role in the growth of thymic epithelial cells.
abstract: Polycomb group gene Bmi1 plays an essential role in HSCs and the BM microenvironment. Recent reports also pointed to the importance of Bmi1 in thymocyte development. However, little is known about its role in the development of the thymic microenvironment. Here, we examined the function of Bmi1 in thymic epithelial cells (TECs) by using the engraftment of fetal thymus (FT) lobes under the kidney capsule. The engrafted Bmi1(-/-) FT lobes were clearly smaller and the number of thymocytes in these lobes was significantly decreased compared with control FT lobes. Analysis of the cell cycle status of TECs in the reconstituted lobes revealed that the reduction of thymus size in Bmi1(-/-) FT grafts was caused by less proliferation of TECs during the early expansion stage. Unlike cases with hematopoietic stem cells or thymocytes, the deletion of p16Ink4a and p19Arf could not restore the defects in Bmi1(-/-) TEC, indicating a distinct role for Bmi1 in TECs. In conclusion, epigenetic regulator polycomb group gene Bmi1 plays a role in the thymic microenvironment in a regeneration process by supporting TEC growth, and thereby contributes to the control of thymus size for T-cell growth in mice.
authors.affiliation: Department of Immunology, Graduate School of Biosciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, Japan.
authors.forename: Yun
authors.initials: Y
authors.lastname: Guo
authors.forename: Masaki
authors.initials: M
authors.lastname: Miyazaki
authors.forename: Manami
authors.initials: M
authors.lastname: Itoi
authors.forename: Rumi
authors.initials: R
authors.lastname: Satoh
authors.forename: Atsushi
authors.initials: A
authors.lastname: Iwama
authors.forename: Takashi
authors.initials: T
authors.lastname: Amagai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawamoto
authors.forename: Masamoto
authors.initials: M
authors.lastname: Kanno
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000276:immunology / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009687:Nuclear Proteins / Q000172:deficiency / Q000276:immunology* / Q000378:metabolism; D063150:Polycomb Repressive Complex 1; D063146:Polycomb-Group Proteins; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000276:immunology* / Q000378:metabolism; D012097:Repressor Proteins / Q000172:deficiency / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction; D013950:Thymus Gland / Q000166:cytology* / Q000254:growth & development / Q000276:immunology* / Q000378:metabolism
chemical_list: C489421:Bmi1 protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D009687:Nuclear Proteins; D063146:Polycomb-Group Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D063150:Polycomb Repressive Complex 1