title: Thymomegaly, microsplenia, and defective homeostatic proliferation of peripheral lymphocytes in p51-Ets1 isoform-specific null mice.
abstract: Ets1 is a member of the Ets transcription factor family. Alternative splicing of exon VII results in two naturally occurring protein isoforms: full-length Ets1 (p51-Ets1) and Ets1(DeltaVII) (p42-Ets1). These isoforms bear key distinctions regarding protein-protein interactions, DNA binding kinetics, and transcriptional target specificity. Disruption of both Ets1 isoforms in mice results in the loss of detectable NK and NKT cell activity and defects in B and T lymphocytes. We generated mice that express only the Ets1(DeltaVII) isoform. Ets1(DeltaVII) homozygous mice express no p51-Ets1 and elevated levels of the p42-Ets1 protein relative to the wild type and display increased perinatal lethality, thymomegaly, and peripheral lymphopenia. Proliferation was increased in both the thymus and the spleen, while apoptosis was decreased in the thymus and increased in the spleen of homozygotes. Significant elevations of CD8(+) and CD8(+)CD4(+) thymocytes were observed. Lymphoid cell (CD19(+), CD4(+), and CD8(+)) reductions were predominantly responsible for diminished spleen cellularity, with fewer memory cells and a failure of homeostatic proliferation to maintain peripheral lymphocytes. Collectively, the Ets1(DeltaVII) mutants demonstrate lymphocyte maturation defects associated with misregulation of p16(Ink4a), p27(Kip1), and CD44. Thus, a balance in the differential regulation of Ets1 isoforms represents a potential mechanism in the control of lymphoid maturation and homeostasis.
authors.affiliation: Hollings Cancer Center, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Higuchi
authors.forename: Frank O
authors.initials: FO
authors.lastname: Bartel
authors.forename: Masahiro
authors.initials: M
authors.lastname: Masuya
authors.forename: Takao
authors.initials: T
authors.lastname: Deguchi
authors.forename: Kelly W
authors.initials: KW
authors.lastname: Henderson
authors.forename: Runzhao
authors.initials: R
authors.lastname: Li
authors.forename: Robin C
authors.initials: RC
authors.lastname: Muise-Helmericks
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kern
authors.forename: Dennis K
authors.initials: DK
authors.lastname: Watson
authors.forename: Demetri D
authors.initials: DD
authors.lastname: Spyropoulos
mesh_terms: D000818:Animals; D001483:Base Sequence; D049109:Cell Proliferation; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D005786:Gene Expression Regulation; D006579:Heterozygote; D006706:Homeostasis; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism; D008214:Lymphocytes / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D010641:Phenotype; D020033:Protein Isoforms / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D050784:Proto-Oncogene Protein c-ets-1 / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D013154:Spleen / Q000166:cytology / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D018960:Hyaluronan Receptors; D020033:Protein Isoforms; D050784:Proto-Oncogene Protein c-ets-1; D050760:Cyclin-Dependent Kinase Inhibitor p27