Similarly, thymic hypocellularity was reproduced following the tissue-specific deletion of gene in the epithelium but not in the thymocyte. is proposed to be important for the maintenance of the stemness of epithelial progenitors. Together, these data establish Cbx4 as a crucial regulator for the generation and maintenance of the thymic epithelium and, hence, for thymocyte development. fetal liver cells (Cor et al., 1997). In this article, we provide evidence that Cbx4 modulates T lymphopoiesis by regulating the proliferation of TECs and the maintenance of the thymic epithelium, thus demonstrating a novel regulatory mechanism for PcG proteins in the immune system. MATERIALS AND METHODS Gene targeting and mice For the disruption of gene, the N-terminal region of the gene including the first two exons and a 0.9 kb upstream region was targeted. Targeted ES clones (MPI-II, 129Sv/Pas derived) were identified by Southern blotting, DBM 1285 dihydrochloride and C57BL/6J blastocytes were used for microinjection. The cassette in the heterozygous was removed by crossed with Actin-Flp mice. EIIa-Cre, Foxn1-Cre or Lck-Cre mice were used for global or conditional knockout, and the mice were bred on the C57BL/6J-129Sv genetic background. The conditional knockout and wild-type mice (for 5 days in the presence of 1.35 mM 2-deoxyguanosine (Sigma). CD24loKit+ hematopoietic progenitor cells (HPCs) were sorted from E13.5-E15.5 fetal livers using a BD FACS Aria flow cytometer, and the purity of the harvested cells was >97% upon reanalysis by flow cytometry. Each thymic lobe was mixed with 4000 HPCs and was cultured in a hanging drop in Terasaki plates for up to 2 days. After further culture on an Isopore membrane, thymic lobes were collected, and cells within each lobe were counted and analyzed using the BD FACSCalibur platform. Statistical analysis Prism software (GraphPad) was used for all statistical analysis. Datasets were compared using a gene (supplementary material Fig. S2A). Homologous recombination was confirmed using Southern blot analysis (supplementary material Fig. S2B), and the null allele was gained upon Cre-mice at E17.5 were decreased by over 85% in comparison with wild-type littermates (Fig. 1B). The hypoplastic thymus did not appear to be the consequence of a general hematopoietic defect because the number of total splenocytes and bone marrow cells in the homozygous pups was comparable with that of the wild-type littermates. To explore the timing of the thymic developmental defect, we performed a histological assessment of the thymus and adjacent structures in E12.5-E15.5 embryos (supplementary material Fig. S3A). In Cbx4-deficient embryos, the separation of the ultimobranchial body rudiments and thymic lobes from the pharynx proceeded normally. However, the growth of the mutant thymus was severely retarded after E13.5, while the wild-type thymus underwent rapid expansion. Therefore, Cbx4 deficiency mainly targeted DBM 1285 dihydrochloride the late development of the fetal thymus rather than the initiation of organogenesis. Besides, similar expression patterns of CD31 in the mutant and wild-type fetal thymi indicate that Cbx4 is not essential for the formation of thymic vasculature (supplementary material Fig. S3B,C). Open in a separate window Fig. 1. Neonatal thymic hypoplasia in Cbx4-deficient mice. (A) Gross morphology of thymi from wild-type (+/+), heterozygous (+/-) and homozygous (-/-) mutant newborn mice. (B) Numbers of total viable cells and TECs in one E17.5 thymic lobe. Absolute numbers of TECs (CD45-EpCAMhi) were calculated as (cell frequencytotal number of thymic cells). Rabbit Polyclonal to GPR142 The data are presented as the mean s.d. of five thymi. Different scales are used for total versus the epithelial cells. (C) Altered cell cycle of thymocytes in Cbx4-deficient thymi. The DNA content for individual E17.5 thymocytes was measured by PI staining. DBM 1285 dihydrochloride Numbers, from left to right, indicate the percentages of cells in G0/G1, S and G2/M phases, respectively. (D) Quantification of BrdU-positive cells.