title: Promoter knock-in mutations reveal a role of Mcl-1 in thymocyte-positive selection and tissue or cell lineage-specific regulation of Mcl-1 expression.
abstract: We previously demonstrated that IL-3 stimulates transcription of the antiapoptotic gene mcl-1 via two promoter elements designated as the SIE and CRE-2 sites. To further study the functional role of these two DNA elements, mutant mice with targeted mutations of both SIE and CRE-2 sites (SC mutants) were generated. Homozygous SC mutants manifested a markedly reduced level of Mcl-1 in thymus but not in other major organs such as spleen, liver, lung, or heart. Reduced expression of Mcl-1 in SC mutant thymus resulted in attenuated positive selection of double-positive thymocytes into both CD4 and CD8 lineages, a result likely due to reduced survival of SC mutant double-positive thymocytes that were supposed to be positively selected. In contrast, in the peripheral lymphoid organs, only CD8(+) but not CD4(+) T cells were significantly reduced in homozygous SC mutant mice, a result consistent with a more dramatic decrease both of Mcl-1 expression and cell viability in mutant CD8(+) compared with mutant CD4(+) T cells. Impaired T cell development and peripheral CD8(+) lymphopenia in homozygous SC mutant mice were both cell autonomous and could be rescued by enforced expression of human Mcl-1. Together, the promoter-knock-in mouse model generated in this study not only revealed a role of Mcl-1 in thymocyte-positive selection, but also uncovered that Mcl-1 expression is regulated in a tissue or cell lineage-specific manner.
authors.affiliation: Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Chia-Yu
authors.initials: CY
authors.lastname: Yang
authors.forename: Nai-Hui
authors.initials: NH
authors.lastname: Lin
authors.forename: Jan-Mou
authors.initials: JM
authors.lastname: Lee
authors.forename: Ching-Yu
authors.initials: CY
authors.lastname: Huang
authors.forename: Hsiang-Ju
authors.initials: HJ
authors.lastname: Min
authors.forename: Jeffrey Jong-Young
authors.initials: JJ
authors.lastname: Yen
authors.forename: Nan-Shih
authors.initials: NS
authors.lastname: Liao
authors.forename: Hsin-Fang
authors.initials: HF
authors.lastname: Yang-Yen
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D019070:Cell Lineage / Q000235:genetics* / Q000276:immunology; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology*; D055879:Gene Knock-In Techniques / Q000379:methods; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D009154:Mutation; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009928:Organ Specificity / Q000235:genetics / Q000276:immunology; D011401:Promoter Regions, Genetic; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology* / Q000378:metabolism
chemical_list: C579094:Mcl1 protein, mouse; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2