Studies on cell lines have greatly improved our understanding of many important biological questions.

We have recently identified ␣-galactosylceramide (␣-GalCer) as a specific ligand for an invariant V␣14͞ V␤8.2 T cell receptor exclusively expressed on the majority of V␣14 NKT cells, a novel subset of lymphocytes. Here, we report that ␣-GalCer selectively activates V␣14 NKT cells resulting in prevention of tumor metastasis. The effector mechanisms of the ligand-activated V␣14 NKT cells seem to be mediated by natural killer (NK)-like nonspecific cytotoxicity. Indeed, the cytotoxic index obtained by ␣-GalCeractivated V␣14 NKT cells was reduced by the addition of cold target tumor cells or by treatment with concanamycin A, which inhibits activation and secretion of perforin, but not by mAbs against molecules involved in the NKT cell recognition and conventional cytotoxicity, such as CD1d, V␤8, NK1.1, Ly49C, Fas, or Fas ligand. These results suggest that the ligand-activated V␣14 NKT cells kill tumor cells directly through a CD1d͞V␣14 T cell receptor-independent, NK-like mechanism.A novel lymphoid lineage, V␣14 natural killer (NK) T cells, distinct from other lymphoid cells including T cells, B cells, and NK cells, is characterized by the early development at day 9.5 of gestation before thymus formation (1) and also by coexpression of the NK receptor and a single, invariant T cell receptor (TCR) encoded by V␣14 and J␣281 gene segments (2-4) in association with a highly skewed set of V␤s, mainly V␤8.2 (5-13). Moreover, the generation of V␣14 NKT cells is exclusively dependent on the expression of the invariant V␣14 TCR as evidenced by the fact that V␣14 NKT cells do not develop in the invariant V␣14 TCR-deficient mice (14) and that the forced expression of the invariant V␣14 TCR leads exclusively to V␣14 NKT cell generation and blocks conventional T cell development (15, 16).Although physiological functions of V␣14 NKT cells remain to be elucidated, the extensive analysis has shown that V␣14 NKT cells are able to mediate allograft bone marrow rejection (17), control autoimmune disease development (18,19), and produce large amounts of both interleukin 4 (IL-4) and interferon ␥ (16,20,21). These findings suggest that V␣14-NKT cells play complicated roles in regulating immune responses more than simply as IL-4 or interferon ␥ providers for Th2 or Th1 cell development, respectively, so far reported (22,23). In addition, we have demonstrated recently that V␣14 NKT cells are a primary target of IL-12 and exert a major effector function in IL-12-mediated tumor rejection (14).A ligand for the invariant V␣14͞V␤8.2 TCR exclusively expressed on V␣14 NKT cells has been identified recently to be ␣-galactosylceramide (␣-GalCer) (16). In addition, ␣-GalCer is presented by a monomorphic non-majorhistocompatibility gene complex (non-MHC) class Ib molecule, CD1d, expressed on dendritic cells (DC), and the ligand͞CD1 complex selectively stimulates to proliferate V␣14 NKT cells but not other lymphocytes only if costimulatory signals generated by CD40͞CD40 ligand and B7͞ CD28 interactions are provided (16). The results suggest th...

SummaryRepetitive sequences account for more than 50% of the human genome. Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal-dominant disease associated with reduction in the copy number of the D4Z4 repeat mapping to 4q35. By an unknown mechanism, D4Z4 deletion causes an epigenetic switch leading to de-repression of 4q35 genes. Here we show that the Polycomb group of epigenetic repressors targets D4Z4 in healthy subjects and that D4Z4 deletion is associated with reduced Polycomb silencing in FSHD patients. We identify DBE-T, a chromatin-associated noncoding RNA produced selectively in FSHD patients that coordinates de-repression of 4q35 genes. DBE-T recruits the Trithorax group protein Ash1L to the FSHD locus, driving histone H3 lysine 36 dimethylation, chromatin remodeling, and 4q35 gene transcription. This study provides insights into the biological function of repetitive sequences in regulating gene expression and shows how mutations of such elements can influence the progression of a human genetic disease.

Embryonic stem (ES) cells have a potential to differentiate into various progenitor cells.Here we investigated the differentiation capacity of mouse ES cells into hepatocytes both in vitro and in vivo. During the culture of embryoid bodies (EBs) derived from ES cells, albumin (ALB) messenger RNA (mRNA) was expressed within 12 days after removal of leukemia inhibitory factor, and ␣-fetoprotein (AFP) mRNA was observed within 9 days without additional exogenous growth factors. In ES cells and early EBs, by contrast, neither ALB mRNA nor AFP mRNA was observed. ALB protein was first detected at day 15 and the level increased with the culture period. The differentiation of EBs facilitated the synthesis of urea with the culture period, whereas early EBs and ES cells produced no urea. These results suggest that cultured EBs contain hepatocytes capable of producing ALB and urea. ES cells and the isolated cells from EBs were transplanted through portal vein to the liver after 30% partial hepatectomy of female mice pretreated with 2-acetylaminofluorene. Four weeks after transplantation with isolated cells from day-9 EBs, ES-derived cells containing Y-chromosome in the liver were positive for ALB (0.2% of total liver cells), whereas teratoma was found in mice transplanted with ES cells or EBs up to day 6. The incidence of teratoma was decreased with the culture duration and no teratoma was observed in the liver transplanted with isolated cells from day-9 EBs. In conclusion, our in vitro and in vivo experiments revealed that cultured EBs contain functional hepatocytes or hepatocyte-like cells. (HEPATOLOGY 2002;36:22-29.)

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Inijection of mice transgenic for a class I major histocompatibility complex-restricted T-cell receptor with a soluble peptide antigen from influenza virus nucleoprotein results in clonal depletion of double-positive Immature thymocytes in the thymus and activation of mature T cells in the periphery, accompanied by a transient up-regulation of the T-cell receptor and CD3 and CD8 coreceptor molecules.

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