Impairment of B lymphopoiesis in precocious aging (klotho) mice

Inactivation of the klotho gene in mice results in multiple disorders that resemble human aging after 3 weeks of age. Because hematopoiesis, especially B lymphopoiesis, is affected in humans and mice by aging, we analyzed the hematopoietic state in homozygous klotho (kl/kl) mice. The kl/kl mice showed thymic atrophy and a reduced number of splenocytes. These mice had almost the normal number of myeloid cells, erythroid cells, IL-3-responsive myeloid precursors and colony forming units in spleen (CFU-S) in bone marrow (BM), but had a substantially decreased number of B cells in BM and peripheral blood as compared with wild-type mice. IL-7-responsive B cell precursors and all of the maturation stages of B cells in BM were also reduced. However, the function of hematopoietic stem cells including their capacity of B lymphopoiesis in vivo and in vitro was normal. Early B cell development was also normal in neonates and young kl/kl mice until 2 weeks old without aging phenotypes. RT-PCR analysis revealed that the level of IL-7 gene expression was significantly reduced in freshly isolated kl/kl BM cells. However, injection of IL-7 in kl/kl mice could not rescue the B lymphopenia. These findings indicate that Klotho protein may regulate B lymphopoiesis via its influence on the hematopoietic microenvironment.

Intramedullary and extramedullary B lymphopoiesis in osteopetrotic mice

Adult bone marrow is a major site for hematopoiesis, and reduction of the bone marrow cavity induces hematopoiesis in extramarrow tissues. To investigate the rudimentary intramarrow and the compensatory extramarrow hematopoiesis, particularly B lymphopoiesis, we used 3 osteopetrotic mouse strains [op/op, mi/mi, and Fos (-/-)], which are severely deficient in functional osteoclasts and therefore form inadequate bone marrow cavities. We found that bone marrow in these osteopetrotic mice supports myelopoiesis but not B lymphopoiesis, although cells that have the potential to differentiate into B lineage cells are present in the bone marrow. Although B lymphopoiesis normally occurs both in the spleen and liver of newborn mice, compensatory B lymphopoiesis in adult op/op and mi/mi mice is observed only in the liver, while myelopoiesis is enhanced in both organs. Interestingly, mice lacking the Fos proto-oncogene exhibit B lymphopoiesis in the spleen as well as liver. The amounts of expression of steel factor, Flt3/Flk-2 ligand, and interleukin-7 in the bone marrow, spleen, or liver were not significantly affected in these osteopetrotic mutants. These findings suggest that the volume of the bone marrow cavity regulates B lymphopoiesis without affecting the production of certain hematopoietic growth factors. The splenic microenvironments that support both myelopoiesis and B lymphopoiesis in the neonatal stage are lost in adults and are not reactivated even in the osteopetrotic adults unless the Fos gene is disrupted.

A novel nuclear phosphoprotein, GANP, is up-regulated in centrocytes of the germinal center and associated with MCM3, a protein essential for DNA replication

Antigen (Ag) immunization induces formation of the germinal center (GC), with large, rapidly proliferating centroblasts in the dark zone, and small, nondividing centrocytes in the light zone. We identified a novel nuclear protein, GANP, that is up-regulated in centrocytes. We found that GANP was up-regulated in GC B cells of Peyer's patches in normal mice and in spleens from Ag-immunized mice. GANP-positive cells appeared in the light zone of the GC, with coexpression of the peanut agglutinin (PNA) (PNA)-positive B220-positive phenotype. The expression of GANP was strikingly correlated with GC formation because Bcl6-deficient mice did not show the up-regulation of GANP. GANP-positive cells were mostly surrounded by follicular dendritic cells. Stimulation with anti-micro and anti-CD40 induced up-regulation of ganp messenger RNA as well as GANP protein in B220-positive B cells in vitro. GANP is a 210-kd protein localized in both the cytoplasm and nuclei, with a homologous region to Map80 that is associated with MCM3, a protein essential for DNA replication. Remarkably, GANP is associated with MCM3 in B cells and MCM3 is also up-regulated in the GC area. These results suggest that the up-regulation of GANP might participate in the development of Ag-driven B cells in GCs through its interaction with MCM3.

Increased c-Fos/activator protein-1 confers resistance against anergy induction on antigen-specific T cell

We have studied the contribution of c-Fos/activator protein-1 (AP-1) to antigen-specific T cell response with reference to T cell anergy by increasing c-Fos/AP-1 in vivo and in vitro. First, after injection of a high dose of staphylococcus enterotoxin B (SEB), clonal deletion of SEB-reactive V(beta)8(+) CD4 T cells occurred both in control B6 and H2-c-fos transgenic (fos) mice, whereas proliferation of T cells against SEB was profoundly depressed in B6 but not in fos mice. Second, the keyhole limpet hemocyanin-specific CD4 T(h)1 cell clone produced decreasing amounts of IL-2 in response to increasing amounts of concanavalin A (Con A) in vitro, whereas the decrease was less significant in the T(h)1 clones stably transfected with c-fos gene. Electrophoretic mobility shift assay with nuclear protein from the transformants showed that overexpression of the c-fos gene compensated the amounts of AP-1 in the nuclei of Con A-treated T(h)1 clones. Thus, increased c-Fos/AP-1 confers resistance against anergy induction on antigen-specific T cells.

Hepatitis C virus structural proteins induce liver cell injury in transgenic mice

To develop an animal model of hepatitis C virus (HCV) infection, transgenic mice carrying part of the HCV cDNA (C980) encoding HCV-core and envelope proteins under control of the mouse class I major histocompatibility complex gene (H-2K) regulatory region were produced. HCV-C980 RNA and HCV-core protein were present in livers from line H36 as determined by RNase protection assay and immunostaining, respectively. More than 40 animals from line H36 were examined histologically. Most of these H36 mice after 10 months of age developed spontaneous focal infiltration of lymphocytes, hepatocyte necrosis, degeneration, and altered foci with mitotic hepatocytes. These pathological lesions were absent in livers from the age-matched control littermates. Liver cells from these H36 mice were sensitive to damage induced by intravenous administration of an anti-Fas antibody. It is suggested that HCV-C980 proteins by themselves may be one causative agent of liver cell injury in subjects with HCV infection.

Single cell analysis of T cells infiltrating labial salivary glands from patients with Sjögren's syndrome

Sjögren's syndrome (SS) is an autoimmune disease characterized by lymphocytic infiltration into the lacrimal and salivary glands leading to symptomatic dry eyes and mouth. To analyze the function of T cells infiltrating the labial salivary glands, we analyzed T cell receptor (TCR) beta and alpha chains, the expression of various cytokine mRNAs, and apoptosis associated genes in predominant TCR BV2+ T cells in the labial salivary glands of patients with SS at the single cell level. TCR BV2+ T cells in the labial salivary glands were sorted as single cells by flow-cytometry, and then examined by a single cell polymerase chain reaction (PCR). We isolated 18 TCR BV2+ T cell clones from three patients with SS. In six clones, there were highly conserved amino acid motifs (RDxG, GNT, QGxxQETQ) in the CDR3 region of the TCR beta chain. Three of the six clones showed conserved amino acids (EDxTG, or ExxTG) in the CDR3 region of the TCR alpha chain, suggesting restricted T cell epitopes. All TCR BV2+ clones expressed IL-2 mRNA, and six clones were able to produce IL-4, indicating that the cells were Th0 type T cells. All TCR BV2+ clones in the labial salivary glands were CD4+ T cells, and ten clones overexpressed Fas antigen at the mRNA level. In contrast, only one clone expressed Fas-ligand (Fas-L) mRNA, and neither perforin nor granzyme A/B was expressed. In conclusion, these findings support the notion that TCR BV2+ T cells that infiltrate labial salivary glands recognize restricted epitopes and function as CD4+ Th0 type T cells in the induction phase of autoimmunity.

Hepatitis C virus structural proteins induce liver cell injury in transgenic mice

To develop an animal model of hepatitis C virus (HCV) infection, transgenic mice carrying part of the HCV cDNA (C980) encoding HCV-core and envelope proteins under control of the mouse class I major histocompatibility complex gene (H-2K) regulatory region were produced. HCV-C980 RNA and HCV-core protein were present in livers from line H36 as determined by RNase protection assay and immunostaining, respectively. More than 40 animals from line H36 were examined histologically. Most of these H36 mice after 10 months of age developed spontaneous focal infiltration of lymphocytes, hepatocyte necrosis, degeneration, and altered foci with mitotic hepatocytes. These pathological lesions were absent in livers from the age-matched control littermates. Liver cells from these H36 mice were sensitive to damage induced by intravenous administration of an anti-Fas antibody. It is suggested that HCV-C980 proteins by themselves may be one causative agent of liver cell injury in subjects with HCV infection.

A single cell analysis of TCR AV24AJ18+ DN T cells

The T-cell receptor (TCR) BV gene of human TCR AV24+ double-negative (DN) T cells, a novel subset of natural killer (NK) T cells, was investigated by single-cell sorting and single-cell polymerase chain reaction (PCR) methods. Seven of eleven TCR AV24+ DN T-cell clones utilized TCR BV8, three BV9, and one BV6. Six of seven TCR AV24/BV8+ DN T-cell clones had identical TCR beta and alpha chains, indicating that they were the same clone. All three TCR AV24/BV9+ DN T-cell clones also demonstrated the same amino acids in the CDR3 region. These findings strongly suggest that the usage of TCR beta and alpha chains on TCR AV24+ DN T cells is extremely restricted, supporting the notion that these cells recognize highly limited T-cell epitopes on antigens. All TCR AV24+ clones expressed the NKR-P1A mRNA, and so were true NK T cells. IL-2 and IL-4 mRNAs were detected in all clones, suggesting that the majority of these cells were Th0-type T cells. Six clones overexpressed Fas-ligand (Fas-L) mRNA and Fas antigen was detected on all clones at the mRNA level. In conclusion, TCR AV24+ DN T cells might recognize restricted T-cell epitopes on antigens and function as Th0-type T cells, inducer cells to Th1- or Th2-type T cells (regulatory T cells), and as Fas-L-positive cytolytic T cells.

An enhancer element for expression of the Ncx (Enx, Hox11L1) gene in neural crest-derived cells

The murine Ncx (Enx, Hox11L1) gene is specifically expressed in a neuronal subset of neural crest-derived tissues. In attempts to elucidate the regulatory DNA element of the tissue-specific expression, we sequenced the 5'-flanking region of the Ncx gene. The transcriptional initiation site was determined at 297 nucleotides (-297) upstream from the ATG start codon (+1). A retinoic acid response element was located on the region between -1163 and -1150. Transient transfection assays with the 5'-flanking sequences fused to the luciferase gene showed that the region between -1387 and -1368 was crucial for the tissue-specific enhancer activity. Furthermore, nuclear proteins extracted from neural crest-derived cells such as murine and human neuroblastoma cells bind to the DNA region between -1387 and -1368. This DNA element was also conserved in the 5'-flanking region of the human NCX gene. Our observations strongly suggest that the DNA element (between -1387 and -1368) contributes to tissue-specific expression of the Ncx gene in murine and human species.

The role of Bcl6 in mature cardiac myocytes

OBJECTIVE

The Bcl6 gene encodes a sequence-specific transcriptional repressor and is ubiquitously expressed in adult murine tissues including heart muscle. The objective of this study was to examine the role of Bcl6 in cardiac myocytes.

METHOD

We developed Bcl6-deficient (Bcl6-/-) mice and histologically examined hearts from these mice.

RESULTS

Massive myocarditis with eosinophilic infiltration occurred in Bcl6-/- mice after 4-6 weeks of age. Since expression of the Bcl6 gene was induced in normal cardiac myocytes after 2 weeks of age and thereafter detected through adulthood, loss of Bcl6 in mature cardiac myocytes may be related to the induction of eosinophilic myocarditis. To examine the effects of eosinophils from Bcl6-/- mice on normal hearts, bone marrow cells from Bcl6-/- mice were adoptively transferred into sublethally irradiated RAG1-deficient mice. Although massive eosinophilic infiltration was detected in conjunctivas and spleens from the chimeric mice, myocarditis was never observed. Electron microscopic analysis of cardiac myocytes from Bcl6-/- mice revealed a spectrum of degenerative changes prior to eosinophilic infiltration.

CONCLUSION

Bcl6 maynot be essential for the maturation of cardiac myocytes but may play a role in protecting mature cardiac myocytes from eosinophilic inflammation.

Enlargement of the globe with ocular malformations in c-Myc transgenic mice

PURPOSE

To study the ocular development in transgenic mice carrying the mouse c-myc gene under the control of the Mx gene promoter (Mx-c-myc).

METHODS

Transgenic mice were generated by standard techniques. For histological studies, the tissues were fixed with 10% buffered formalin, embedded in paraffin according to the standard procedure and sliced in 4-microm sections. c-Myc expression was investigated by reverse transcriptase-polymerase chain reaction and Southern blot analysis.

RESULTS

A line of the Mx-c-myc mice displayed progressive enlargement of the globe with other ocular malformations. Histologically, the enlarged eyes exhibited closed cornea-iris angle, microphakia, corneal epithelial disorders, and attenuation of the inner retinal layers. Developmental analysis of eyes from these Mx-c-myc mice revealed irregular development of the iris and ciliary body at embryonic day 15.5 and the closed angle at 1 week of age. Leaky exogenous c-myc expression was detected in cornea, iris, lens, and retina from the Mx-c-myc mice by reverse transcriptase-polymerase chain reaction and Southern blot analysis. No other developmental abnormalities were observed in the Mx-c-myc mice. The anterior segment of the enlarged eyes showed the closed angle with elongation of the iris and ciliary body. There was no attenuation in the outer retinal layers from the outer plexiform layer to the retinal pigment epithelium.

CONCLUSIONS

We conclude that the buphthalmos and accompanying changes were not due to expression of the exogenous c-myc in cornea and retina but may be the secondary changes of elevated intraocular pressure. We suggest that Mx-c-myc mice can serve as a useful model for investigating the development of the anterior segment and the genesis of buphthalmos.

Expression of a murine homologue of the inhibitor of apoptosis protein is related to cell proliferation

The inhibitor of apoptosis (IAP) proteins form a highly conserved gene family that prevents cell death in response to a variety of stimuli. Herein we describe a newly defined murine IAP, designated Tiap, that proved to be a murine homologue of human survivin based on sequence comparison. TIAP has one baculovirus IAP repeat and lacks a C-terminal RING finger motif. TIAP interacted with the processed form of caspase 3 and inhibited caspase-induced cell death. Histological examinations revealed that TIAP is expressed in growing tissues such as thymus, testis, and intestine of adult mice and many tissues of embryos. In in vitro studies, TIAP was induced in splenic T cells activated with anti-CD3 antibody or Con A, and the expression of TIAP was up-regulated in synchronized NIH 3T3 cells at S to G2/M phase of the cell cycle. We propose that during cell proliferation, cellular protective activity may be augmented with inducible IAPs such as TIAP.

Prolonged expression of c-fos suppresses cell cycle entry of dormant hematopoietic stem cells

The proto-oncogene c-fos was transiently upregulated in primitive hematopoietic stem (Lin-Sca-1(+)) cells stimulated with stem cell factor, interleukin-3 (IL-3), and IL-6. To investigate a role of the c-fos in hematopoietic stem cells, we used bone marrow (BM) cells from transgenic mice carrying the c-fos gene under the control of the interferon-alpha/beta-inducible Mx-promoter (Mx-c-fos), and fetal liver cells from c-fos-deficient mice. Prolonged expression of the c-fos in Lin-Sca-1(+) BM cells inhibited factor-dependent colony formation and hematopoiesis on a stromal cell layer by keeping them at G0/G1 phase of the cell cycle. These Lin-Sca-1(+) BM cells on a stromal layer entered into the cell cycle whenever exogenous c-fos was downregulated. However, ectopic c-fos did not perturb colony formation by Lin-Sca-1(+) BM cells after they entered the cell cycle. Furthermore, endogenous c-fos is not essential to cell cycle progression of hematopoietic stem cells because the factor-dependent and the stroma-dependent hematopoiesis by Lin-Sca-1(+) fetal liver cells from c-fos-deficient mice was not impaired. These results suggest that the c-fos induced in primitive hematopoietic stem cells negatively controls cell cycle progression and maintains them in a dormant state.

Introduction of an osteopontin gene confers the increase in B1 cell population and the production of anti-DNA autoantibodies

Osteopontin (OPN) is an Arg-Gly-Asp-containing phosphoprotein that is secreted by activated T cells. The concentration of serum OPN protein is elevated in autoimmune-prone MRL-lpr mice as well as in patients with systemic lupus erythematosus. Previously, it was shown that OPN induces the polyclonal activation of B cells, resulting in the augmented production of immunoglobulin, indicating that OPN plays some role in the development of autoimmune disease. However, the link between OPN and development of autoimmune disease remains unclear. To analyze the role of OPN in immune system and autoimmune diseases, we have generated two kinds of transgenic mice: one carries the immunoglobulin (Ig) enhancer/SV40 promoter and the other carries the cytomegalovirus enhancer/chicken beta-actin (CAG) promoter. In both groups of transgenic mice, the B1 cell population in peritoneal cavity was markedly increased and titer of IgM and IgG3 antibodies in the serum was considerably higher than that in wild-type mice. Most important, the titer of the IgM class of anti-double-stranded DNA antibody was significantly elevated in transgenic mice. These results strongly suggest that OPN may have an important role in the propagation and differentiation of B1 cells and production of autoantibodies.

c-Fos induces apoptosis in germinal center B cells

We examined the role of c-Fos in the differentiation of mature B cells into IgG-producing cells using transgenic mice carrying the c-fos gene under the control of the IFN-alpha/beta-inducible Mx promoter (Mx-c-fos) or the constitutive H-2Kb promoter (H2-c-fos). Splenic B cells from Mx-c-fos mice were cultured with LPS and rIL-4, and IgG1+ B cells were developed in the culture after day 3. When IFN-alpha/beta was added to the culture from day 2, development of IgG1+ B cells was perturbed, and the number of apoptotic cells increased within 24 h, suggesting that c-Fos induces apoptosis in Ig class-switching B cells. To confirm the effect of c-Fos on B cell differentiation in vivo, H2-c-fos mice were immunized with DNP-OVA. The mice produced primary IgM, but not IgG, anti-DNP Ab in serum and failed to generate germinal centers in spleen. The perturbation of germinal center formation in H2-c-fos mice was rescued by mating them with transgenic mice carrying the bcl-2 gene with the Ig promoter. However, primary IgG1 anti-DNP Ab production was still suppressed in doubly transgenic mice, suggesting that Bcl-2 can delay the time of c-Fos-induced apoptosis in Ig class-switching B cells but cannot rescue the death. Since c-Fos is induced in mature B cells reacted with Ags, and clonal deletion of self-reactive B cells in germinal centers is insensitive to Bcl-2, these results suggest that c-Fos plays a causal role in clonal deletion of germinal center B cells.

mel-18 negatively regulates cell cycle progression upon B cell antigen receptor stimulation through a cascade leading to c-myc/cdc25

mel-18 is a mammalian Polycomb group gene encoding a transcriptional repressor with tumor suppressive activity. Overexpression of mel-18 in mice results in cell cycle arrest of B cells upon B cell receptor stimulation with downregulation of c-myc. This phenotype is rescued in mel-18/c-myc double-transgenic mice, suggesting that c-myc locates downstream of mel-18. In mel-18 transgenic mice, the downregulation of cyclins D2 and E; CDK4, -6, and -7; and CDC25A causes the impairment in the activities of cyclin-dependent kinases, resulting in hypophosphorylation of the retinoblastoma protein. In contrast, the upregulation of c-Myc, CDC25, and CDC2/CDK2 kinase activities results in the augmentation of B cell proliferation in mel-18-deficient mice. We therefore propose that mel-18 negatively regulates the cell cycle through a c-myc/cdc25 cascade.

BAZF, a novel Bcl6 homolog, functions as a transcriptional repressor

The BCL6 gene, which has been identified from the chromosomal translocation breakpoint in B-cell lymphomas, functions as a sequence-specific transcriptional repressor. We cloned a novel Bcl6-homologous gene, BAZF (encoding Bcl6-associated zinc finger protein). The predicted amino acid sequence of BAZF indicated that the BTB/POZ domain and the five repeats of the Krüppel-like zinc finger motif are located in the NH2-terminal region and the COOH-terminal region, respectively. BAZF associated with Bcl6 at the BTB/POZ domain and localized in the nucleus. Since zinc finger motifs of BAZF were 94% identical to those of Bcl6 at the amino acid level, BAZF bound specifically to the DNA-binding sequence of Bcl6 and functioned as a transcriptional repressor. The repressor activity was associated with both the BTB/POZ domain and the middle portion of BAZF. The 17-amino-acid sequence in the middle portion was completely conserved between BAZF and Bcl6, and the conserved region was critical for the repressor activity. Expression of BAZF mRNA, like that of Bcl6 mRNA, was induced in activated lymphocytes as an immediate-early gene. Therefore, the biochemical character of BAZF is similar to that of Bcl6 although the tissue expression pattern of BAZF differs from that of Bcl6. This is apparently the first report of a gene family whose members encode zinc finger proteins with the BTB/POZ domain.

A physiologic role of Bcl-xL induced in activated macrophages

Activated macrophages produce nitric oxide (NO) that is an important effector molecule for their antimicrobial and antitumor activities. Since this NO is also toxic for themselves, they have self-defense mechanisms. To elucidate the mechanisms in a physiologic condition, expression of bcl-2 family genes were examined in peritoneal macrophages and RAW264 macrophage cell line activated with IFN-gamma and LPS. Bcl-xL, but not bcl-2 and bax mRNA, was highly inducible within 3 h after stimulation. The induction required new protein synthesis, but was independent of effects of synthesized NO. Since activated RAW264 were more resistant to NO-induced apoptosis mediated by the exposure to S-nitroso-N-acetyl-penicillamine (SNAP) than nonactivated RAW264, the inducible Bcl-xL may play a role in the protection from NO toxicity. To confirm the protective function, RAW264 were stably transfected with bcl-xL. Those transfectants activated with IFN-gamma and LPS appeared highly resistant to NO-induced cell death detected within 24 h after stimulation, although their NO production was similar to those of parental RAW264 and neomycin control-transfected cells. Furthermore, bcl-xL transfectants displayed substantial protection from SNAP-induced apoptosis. These results establish a link between self-defense to the synthesized NO and the induction of Bcl-xL in activated macrophages.

A novel pathogenesis of megacolon in Ncx/Hox11L.1 deficient mice

The Ncx/Hox11L.1 gene, a member of the Hox11 homeobox gene family, is mainly expressed in neural crest-derived tissues. To elucidate the role of Ncx/Hox11L.1, the gene has been inactivated in embryonic stem cells by homologous recombination. The homozygous mutant mice were viable. These mice developed megacolon with enteric ganglia by age 3-5 wk. Histochemical analysis of the ganglia revealed that the enteric neurons hyperinnervated in the narrow segment of megacolon. Some of these neuronal cells degenerated and neuronal cell death occurred in later stages. We propose that Ncx/Hox11L.1 is required for maintenance of proper functions of the enteric nervous system. These mutant mice can be used to elucidate a novel pathogenesis for human neuronal intestinal dysplasia.

Disruption of the Bcl6 gene results in an impaired germinal center formation

The Bcl6 gene has been identified from the chromosomal translocation breakpoint in B cell lymphomas, and its products are expressed highly in germinal center (GC) B cells. To investigate the function of Bcl6 in lymphocytes, we have generated RAG1-deficient mice reconstituted with bone marrow cells from Bcl6-deficient mice (Bcl6(-/-)RM). Lymphogenesis in primary lymphoid tissues of Bcl6(-/-)RM is normal, and Bcl6(-/-)RM produced control levels of primary IgG1 antibodies specific to T cell-dependent antigens. However, GCs were not found in these mice. This defect was mainly due to the abnormalities of B cells. Therefore, Bcl6 is essential for the differentiation of GC B cells.

A negative regulatory region of the murine Hox11 gene

The HOX11 gene was isolated from the chromosomal breakpoint of human T cell acute lymphoblastic leukemias with a chromosomal translocation t(10;14). Expression of this proto-oncogene is strictly controlled in normal tissues. However, regulatory elements of the gene have never been studied. Since the HOX11 gene is well conserved between human and murine, we sequenced 5' flanking region of the murine Hox11 gene and analyzed the elements. We identified the transcription start site (+1) of the gene using mRNA from fetal spleens by primer extension analysis. The start site was determined at 795 bp upstream from the ATG site. A typical TATA box sequence was found at 35 bp upstream from the start site. Furthermore, promoter activity of the 5' flanking region of the start site was monitored by luciferase assay. The activity mainly located within a 540-bp fragment immediately upstream from the start site (-540 to +1). The (-1240 to -540) region contained a negative regulatory element of the transcription. The TATA box sequence and the nucleotide sequence around the transcription start site were conserved in the human HOX11 gene. The transcription start site of the human HOX11 gene in normal tissues is discussed.

Ncx, a Hox11 related gene, is expressed in a variety of tissues derived from neural crest cells

We have isolated the murine homeobox gene (Ncx) that belong to a Hox11 gene family. Expression of the Ncx gene was analyzed in total RNAs from embryos by reverse transcribed polymerase chain reaction (RT-PCR). The mRNA was detected in embryos after 9.5 days of embryogenesis (E9.5) and was maximal at E12.5. The RT-PCR also detected the message in total RNAs from adrenal glands and intestine in adult mice. The expression was further examined in various tissues from embryos by in situ hybridization. It was detected in dorsal root ganglia, cranial nerve ganglia (V, IX, X), enteric nerve ganglia and adrenal glands from embryos between E9.5 and E13.5. Since its expression is restricted to tissues derived from neural crest cells, Ncx may play a role in differentiation and proliferation of neural crest lineage cells.

Phenotypes and invariant alpha beta TCR expression of peripheral V alpha 14+ NK T cells

A novel subset of peripheral T cells, peripheral NK T cells, is found to be a major population comprising 5% of splenic T and 40% of bone marrow T cells. The majority of peripheral NK T cells are characterized by the expression of an invariant TCR-alpha encoded by V alpha 14/J alpha 281 with a one nucleotide N region. Moreover, a specific reduction of V alpha 14+ NK T cells has been demonstrated to be tightly associated with various autoimmune diseases, indicating their decisive role in autoimmune disease development. In this study, we investigated the phenotypes of peripheral V alpha 14+ NK T cells and their TCR-beta repertoire. Peripheral V alpha 14+ NK T cells, comprise two populations, i.e., small and large sized cells, at an equal frequency, belonged to the CD4- CD8- fraction, and are heat stable antigen(bright), macrophage-1bright, B220bright, CD45RBdim, and Mel-14dim, but CD5-, distinct from thymic NK T cells. TCR-beta analysis clearly showed that peripheral V alpha 14+ NK T cells utilized two to three dominant invariant TCR-beta, such as V beta 8.2 D beta J beta 2.5/V beta 7 D beta J beta 2.1 in the spleen and liver, V beta 8.2 D beta J beta 2.5/V beta 8.3 D beta J beta 2.2/V beta 7 D beta J beta 2.6 in the bone marrow, and V beta 7 D beta J beta 2.1/V beta 3 D beta J beta 1.2 in intestinal intraepithelial lymphocytes. Judging from the unusual surface phenotypes, such as heat stable antigen, macrophage-1, B220, CD45RBdim, and Mel-14dim, which are known to be T cell activation markers, peripheral V alpha 14+ NK T cells may always be activated under physiologic conditions, resulting in the oligoclonal expansion of V alpha 14+ NK T cells with different invariant TCR-beta in different peripheral organs. The unique features of V alpha 14+ NK T cells are discussed.

Overexpression of c-fos inhibits down-regulation of a cyclin-dependent kinase-2 inhibitor p27Kip1 in splenic B cells activated by surface Ig cross-linking

Splenic B cells activated by surface Ig (sIg) cross-linking transiently express the c-fos gene within 0.5 h and then enter into S phase of the cell cycle within 48 h. To investigate a role of c-fos in cell cycle progression, we used splenic B cells from IFN-alphabeta-inducible c-fos transgenic mice (Mx-c-fos). In the absence of IFN, the cell cycle progression of Mx-c-fos B cells stimulated with anti-IgM Ab was similar to that in control B cells. The cell cycle was arrested in G1 phase when we added IFN to the culture within 12 h after anti-IgM Ab stimulation, suggesting that overexpression of c-fos until mid-G1 phase perturbs activation of the cell cycle regulatory machinery. In control B cells, cyclin E and cdk2 were induced within 24 to 48 h after stimulation, and this induction was accompanied by down-regulation of a cdk2 inhibitor p27Kip1. As a consequence of these activation processes, cdk2 kinase activity was induced in B cells in the late G1 phase. However, kinase activity was not detected in Mx-c-fos B cells, presumably because the down-regulation of p27 was perturbed. These data suggest that c-Fos can negatively control cell cycle regulatory machinery in sIg-stimulated B cells.

Phenotypes and invariant alpha beta TCR expression of peripheral V alpha 14+ NK T cells

A novel subset of peripheral T cells, peripheral NK T cells, is found to be a major population comprising 5% of splenic T and 40% of bone marrow T cells. The majority of peripheral NK T cells are characterized by the expression of an invariant TCR-alpha encoded by V alpha 14/J alpha 281 with a one nucleotide N region. Moreover, a specific reduction of V alpha 14+ NK T cells has been demonstrated to be tightly associated with various autoimmune diseases, indicating their decisive role in autoimmune disease development. In this study, we investigated the phenotypes of peripheral V alpha 14+ NK T cells and their TCR-beta repertoire. Peripheral V alpha 14+ NK T cells, comprise two populations, i.e., small and large sized cells, at an equal frequency, belonged to the CD4- CD8- fraction, and are heat stable antigen(bright), macrophage-1bright, B220bright, CD45RBdim, and Mel-14dim, but CD5-, distinct from thymic NK T cells. TCR-beta analysis clearly showed that peripheral V alpha 14+ NK T cells utilized two to three dominant invariant TCR-beta, such as V beta 8.2 D beta J beta 2.5/V beta 7 D beta J beta 2.1 in the spleen and liver, V beta 8.2 D beta J beta 2.5/V beta 8.3 D beta J beta 2.2/V beta 7 D beta J beta 2.6 in the bone marrow, and V beta 7 D beta J beta 2.1/V beta 3 D beta J beta 1.2 in intestinal intraepithelial lymphocytes. Judging from the unusual surface phenotypes, such as heat stable antigen, macrophage-1, B220, CD45RBdim, and Mel-14dim, which are known to be T cell activation markers, peripheral V alpha 14+ NK T cells may always be activated under physiologic conditions, resulting in the oligoclonal expansion of V alpha 14+ NK T cells with different invariant TCR-beta in different peripheral organs. The unique features of V alpha 14+ NK T cells are discussed.