Purification and analysis of RIN family-novel Rab5 GEFs

The small GTPase Rab5 plays important roles in membrane budding and trafficking in the early endocytic pathways, and the activation of this GTPase is mediated by several guanine nucleotide exchange factors (GEFs) at each of the transport steps. The RIN family has been identified as GEFs for Rab5 and shown to possess unique biochemical properties. The RIN family preferentially interacts with an activated form of Rab5, although it enhances guanine nucleotide exchange reaction. Moreover, biochemical analysis indicates that the RIN family functions as a tetramer. In this chapter, we describe the isolation of the recombinant RIN family via expression in Spodoptera frugiperda (Sf9) insect cells and in mammalian cells. In addition, functional analysis is also provided to assess the physiological properties of the RIN family.

Development of cell therapy using autologous bone marrow cells for liver cirrhosis

The plasticity of bone marrow has been confirmed by the autopsy of a female recipient of bone marrow cell transplantation from a male donor. To establish new clinical cell therapies using autologous bone marrow cells for patients with liver failure, we developed a new in vivo model named the green fluorescent protein (GFP)/carbon tetrachloride (CCl4) model. Using the GFP/CCl4 model, we found that transplanted Liv8-negative cells efficiently repopulated into cirrhotic liver tissue and differentiated into albumin-producing hepatocytes under persistent liver damage induced by carbon tetrachloride. Moreover, bone marrow cell transplantation into mice with liver cirrhosis improved liver function and liver fibrosis with the strong expression of matrix metalloproteinases (MMPs), especially MMP-9 activity, resulting in an improved survival rate. Results from the GFP/CCl4 model showed that cell therapy using autologous bone marrow cells has the potential to become an effective treatment for patients with liver failure. A summary of findings from the GFP/CCl4 model is described.

Autoamplification of NFATc1 expression determines its essential role in bone homeostasis

NFATc1 and NFATc2 are functionally redundant in the immune system, but it was suggested that NFATc1 is required exclusively for differentiation of osteoclasts in the skeletal system. Here we provide genetic evidence that NFATc1 is essential for osteoclast differentiation in vivo by adoptive transfer of NFATc1^−/− hematopoietic stem cells to osteoclast-deficient Fos^−/− mice, and by Fos^−/− blastocyst complementation, thus avoiding the embryonic lethality of NFATc1^−/− mice. However, in vitro osteoclastogenesis in NFATc1-deficient cells was rescued by ectopic expression of NFATc2. The discrepancy between the in vivo essential role of NFATc1 and the in vitro effect of NFATc2 was attributed to selective autoregulation of the NFATc1 gene by NFAT through its promoter region. This suggested that an epigenetic mechanism contributes to the essential function of NFATc1 in cell lineage commitment. Thus, this study establishes that NFATc1 represents a potential therapeutic target for bone disease and reveals a mechanism that underlies the essential role of NFATc1 in bone homeostasis.

Lesson from the GFP/CCl4 model--translational research project: the development of cell therapy using autologous bone marrow cells in patients with liver cirrhosis

The plasticity of bone marrow has been confirmed by the analysis of autopsy findings in female recipients of bone marrow cells transplanted from male donors. To establish new clinical cell therapies using autologous bone marrow cells for patients with liver failure, we developed a new in vivo model, the "green fluorescent protein (GFP)/carbon tetrachloride (CCl(4)) model". Using the GFP/CCl(4) model, we found that transplanted Liv8-negative cells efficiently repopulated into cirrhotic liver tissue and trans-differentiated into albumin-producing hepatocytes under conditions of persistent liver damage induced by CCl(4). Moreover, one marrow cell transplantation into liver cirrhosis mice improved their liver function, ameliorated liver fibrosis, and improved their survival rate. Results from the GFP/CCl(4) model showed that cell therapy using autologous bone marrow cells has the potential to become an effective treatment for patients with liver failure. Here we describe the findings from the GFP/CCl(4) model and the scope of the translational research project.

Fibroblast growth factor 2 facilitates the differentiation of transplanted bone marrow cells into hepatocytes

We have developed an in vivo mouse model, the green fluorescent protein (GFP)/carbon tetrachloride (CCl(4)) model, and have previously reported that transplanted GFP-positive bone marrow cells (BMCs) differentiate into hepatocytes via hepatoblast intermediates. Here, we have investigated the growth factors that are closely related to the differentiation of transplanted BMCs into hepatocytes, and the way that a specific growth factor affects the differentiation process in the GFP/CCl(4) model. We performed immunohistochemical analysis to identify an important growth factor in our model, viz., fibroblast growth factor (FGF). In liver samples, the expression of FGF1 and FGF2 and of FGF receptors (FGFRs; FGFR1, FGFR2) was significantly elevated with time after bone marrow transplantation (BMT) compared with other factors, and co-expression of GFP and FGFs or FGFRs could be detected. We then analyzed the effect and molecular mechanism of FGF signaling on the enhancement of BMC differentiation into hepatocytes by immunohistochemistry, immunoblotting, and microarray analysis. Treatment with recombinant FGF (rFGF), especially rFGF2, elevated the repopulation rate of GFP-positive cells in the liver and significantly increased the expression of both Liv2 (hepatoblast marker) and albumin (hepatocyte marker). Administration of rFGF2 at BMT also raised serum albumin levels and improved the survival rate. Transplantation of BMCs with rFGF2 specifically activated tumor necrosis factor-alpha (TNF-alpha) signaling. Thus, FGF2 facilitates the differentiation of transplanted BMCs into albumin-producing hepatocytes via Liv2-positive hepatoblast intermediates through the activation of TNF-alpha signaling. Administration of FGF2 in combination with BMT improves the liver function and prognosis of mice with CCl(4)-induced liver damage.

Human homologue of maid is a useful marker protein in hepatocarcinogenesis

BACKGROUND & AIMS

Human homologue of maid (HHM) is a helix-loop-helix (HLH) transcriptional regulatory protein that is involved in the hepatic stem cell development and differentiation. We analyzed the potential involvement of HHM in hepatocarcinogenesis.

METHODS

We analyzed HHM expression in the choline-deficient L-amino acid defined (CDAA) diet model of rat hepatocarcinogenesis and in human adenomatous hyperplasia (AH) and hepatocellular carcinoma (HCC) biopsy samples. We assessed the effects of HHM on cell proliferation. We screened proteins that bind to HHM protein using a yeast 2-hybrid screen.

RESULTS

High HHM expression was seen in foci and HCC induced in the rat CDAA diet model. HHM protein was expressed in 23 of 32 AH samples (72%), 19 of 28 well-differentiated HCC samples (68%), and 9 of 18 poorly-moderately differentiated HCC samples (50%). Over-expressed HHM enhanced the S phase. HHM interference RNA significantly inhibited cell proliferation. A yeast 2-hybrid screen identified Jun activation domain-binding protein 1 (Jab1) as a binding partner for HHM. We confirmed HHM and Jab1 binding by immunoprecipitation and immunofluorescent histochemistry. The expression of Jab1 was found in human AH and HCC samples. We found an association between levels of expression of HHM and those of Jab1 in AH and HCC tissues examined (P = .027 by chi2 test).

CONCLUSIONS

High-level HHM expression was found from the very early stages of hepatocarcinogenesis, suggesting that HHM may be a useful marker protein to detect.

A systematic genome-wide screen for mutations affecting organogenesis in Medaka, Oryzias latipes

A large-scale mutagenesis screen was performed in Medaka to identify genes acting in diverse developmental processes. Mutations were identified in homozygous F3 progeny derived from ENU-treated founder males. In addition to the morphological inspection of live embryos, other approaches were used to detect abnormalities in organogenesis and in specific cellular processes, including germ cell migration, nerve tract formation, sensory organ differentiation and DNA repair. Among 2031 embryonic lethal mutations identified, 312 causing defects in organogenesis were selected for further analyses. From these, 126 mutations were characterized genetically and assigned to 105 genes. The similarity of the development of Medaka and zebrafish facilitated the comparison of mutant phenotypes, which indicated that many mutations in Medaka cause unique phenotypes so far unrecorded in zebrafish. Even when mutations of the two fish species cause a similar phenotype such as one-eyed-pinhead or parachute, more genes were found in Medaka than in zebrafish that produced the same phenotype when mutated. These observations suggest that many Medaka mutants represent new genes and, therefore, are important complements to the collection of zebrafish mutants that have proven so valuable for exploring genomic function in development.

Novel Role of the Small GTPase Rheb: Its Implication in Endocytic Pathway Independent of the Activation of Mammalian Target of Rapamycin

The Ras-homologous GTPase Rheb that is conserved from yeast to human appears to be involved not only in cell growth but also in nutrient uptake. Recent biochemical analysis revealed that tuberous sclerosis complex (TSC), a GTPase-activating protein (GAP), deactivates Rheb and that phosphatidylinositol 3'-kinase (PI3k)-Akt/PKB kinase pathway activates Rheb through inhibition of the GAP-mediated deactivation. Although mammalian target of rapamycin (mTOR) kinase is implicated in the downstream target of Rheb, the direct effector(s) and exact functions of Rheb have not been fully elucidated. Here we identified that Rheb expression in cultured cells induces the formation of large cytoplasmic vacuoles, which are characterized as late endocytic (late endosome- and lysosome-like) components. The vacuole formation required the GTP form of Rheb, but not the activation of the downstream mTOR kinase. These results suggest that Rheb regulates endocytic trafficking pathway independent of the previously identified mTOR pathway. The physiological roles of the two Rheb-dependent signaling pathways are discussed in terms of nutrient uptake and cell growth or cell cycle progression.

Genetic dissection of the formation of the forebrain in Medaka, Oryzias latipes

The forebrain, consisting of the telencephalon and diencephalon, is essential for processing sensory information. To genetically dissect formation of the forebrain in vertebrates, we carried out a systematic screen for mutations affecting morphogenesis of the forebrain in Medaka. Thirty-three mutations defining 25 genes affecting the morphological development of the forebrain were grouped into two classes. Class 1 mutants commonly showing a decrease in forebrain size, were further divided into subclasses 1A to 1D. Class 1A mutation (1 gene) caused an early defect evidenced by the lack of bf1 expression, Class 1B mutations (6 genes) patterning defects revealed by the aberrant expression of regional marker genes, Class 1C mutation (1 gene) a defect in a later stage, and Class 1D (3 genes) a midline defect analogous to the zebrafish one-eyed pinhead mutation. Class 2 mutations caused morphological abnormalities in the forebrain without considerably affecting its size, Class 2A mutations (6 genes) caused abnormalities in the development of the ventricle, Class 2B mutations (2 genes) severely affected the anterior commissure, and Class 2C (6 genes) mutations resulted in a unique forebrain morphology. Many of these mutants showed the compromised sonic hedgehog expression in the zona-limitans-intrathalamica (zli), arguing for the importance of this structure as a secondary signaling center. These mutants should provide important clues to the elucidation of the molecular mechanisms underlying forebrain development, and shed new light on phylogenically conserved and divergent functions in the developmental process.

Transplantation of bone marrow cells reduces CCl4-induced liver fibrosis in mice

We investigated the effect of bone marrow cell (BMC) transplantation on established liver fibrosis. BMCs of green fluorescent protein (GFP) mice were transplanted into 4-week carbon tetrachloride (CCl4)-treated C57BL6 mice through the tail vein, and the mice were treated for 4 more weeks with CCl4 (total, 8 weeks). Sirius red and GFP staining clearly indicated migrated BMCs existing along with fibers, with strong expression of matrix metalloproteinase (MMP)-9 shown by anti-MMP-9 antibodies and in situ hybridization. Double fluorescent immunohistochemistry showed the expression of MMP-9 on the GFP-positive cell surface. Film in situ zymographic analysis revealed strong gelatinolytic activity in the periportal area coinciding with the location of MMP-9-positive BMCs. Four weeks after BMC transplantation, mice had significantly reduced liver fibrosis, as assessed by hydroxyproline content of the livers, compared to that of mice treated with CCl4 alone. Subpopulation of Liv8-negative BMCs was responsible for this fibrolytic effect. In conclusion, mice with BMC transplants with continuous CCl4 injection had reduced liver fibrosis and a significantly improved survival rate after BMC transplantation compared with mice treated with CCl4 alone. This finding introduces a new concept for the therapy of liver fibrosis.

Molecular signature associated with plasticity of bone marrow cell under persistent liver damage by self-organizing-map-based gene expression

The mechanism that regulates the plasticity of bone marrow cells (BMCs) into hepatocytes is poorly understood. We developed a green fluorescent protein/carbon tetrachloride model to find that BMC transplantation recovered liver damage. Serum albumin level and liver fibrosis were recovered by BMC transplantation. To understand the mechanism, we used DNA-chip technology to profile the change of transient gene expression before and after BMC transplantation. On the basis of gene expression with self-organizing map using specific equation, genes were classified into 153 clusters. The information is useful to understand the dramatic gene activation during the process of the plasticity of BMC.

Requirement of MKK4 and MKK7 for CdCl2- or HgCl2-induced activation of c-Jun NH2-terminal kinase in mouse embryonic stem cells

c-Jun NH(2)-terminal kinase (JNK), also known as stress-activated protein kinase (SAPK), is activated primarily by inflammatory cytokines and environmental stresses including toxic metal exposure. To reveal the upstream kinase responsible for JNK activation by toxic metals, the phosphorylation status and the activity of JNK were examined in mouse embryonic stem (ES) cells lacking MKK4 or MKK7 following exposure to CdCl(2) or HgCl(2). Treatment with CdCl(2) or HgCl(2) induced the phosphorylation of JNK in a dose- and time-dependent manner in wild-type ES cells. In both mkk4(-/-) and mkk7(-/-) ES cells, CdCl(2)- or HgCl(2)-induced phosphorylation and activation of JNK were suppressed significantly. However, in mkk7(-/-) ES cells treated with CdCl(2) and HgCl(2), JNK activation was not abolished (suppressed by 56% and 78%, respectively). These findings suggest that the full activation of JNK by toxic metal exposure requires both MKK4 and MKK7, and these upstream kinases might contribute differentially in JNK activation between mouse ES cells exposed to CdCl(2) and HgCl(2).

Physiological Roles of SAPK/JNK Signaling Pathway

Stress-activated protein kinase/c-Jun NH(2)-terminal kinase (SAPK/JNK) is activated by many types of cellular stresses and extracellular signals. Recent studies, including the analysis with knockout mice, have led to progress towards understanding the physiological roles of SAPK/JNK activation in embryonic development in addition to immune responses. SAPK/JNK activation plays essential roles in organogenesis during mouse development by regulating cell survival, apoptosis, and proliferation. Two SAPK/JNK activators, SEK1 and MKK7, are required for fetal liver formation and full activation of SAPK/JNK, which responds to various stimuli in an all-or-none manner. This article focuses on physiological roles of SAPK/JNK activation in fetal liver formation and in apoptosis regulation.

Mutations affecting liver development and function in Medaka, Oryzias latipes, screened by multiple criteria

We report here mutations affecting various aspects of liver development and function identified by multiple assays in a systematic mutagenesis screen in Medaka. The 22 identified recessive mutations assigned to 19 complementation groups fell into five phenotypic groups. Group 1, showing defective liver morphogenesis, comprises mutations in four genes, which may be involved in the regulation of growth or patterning of the gut endoderm. Group 2 comprises mutations in three genes that affect the laterality of the liver; in kendama mutants of this group, the laterality of the heart and liver is uncoupled and randomized. Group 3 includes mutations in three genes altering bile color, indicative of defects in hemoglobin-bilirubin metabolism and globin synthesis. Group 4 consists of mutations in three genes, characterized by a decrease in the accumulation of fluorescent metabolite of a phospholipase A(2) substrate, PED6, in the gall bladder. Lipid metabolism or the transport of lipid metabolites may be affected by these mutations. Mutations in Groups 3 and 4 may provide animal models for relevant human diseases. Group 5 mutations in six genes affect the formation of endoderm, endodermal rods and hepatic bud from which the liver develops. These Medaka mutations, identified by morphological and metabolite marker screens, should provide clues to understanding molecular mechanisms underlying formation of a functional liver.

Mutations affecting somite formation in the Medaka (Oryzias latipes)

The metameric structure of the vertebrate trunk is generated by repeated formation of somites from the unsegmented presomitic mesoderm (PSM). We report the initial characterization of nine different mutants affecting segmentation that were isolated in a large-scale mutagenesis screen in Medaka (Oryzias latipes). Four mutants were identified that show a complete or partial absence of somites or somite boundaries. In addition, five mutations were found that cause fused somites or somites with irregular sizes and shapes. In situ hybridization analysis using specific markers involved in the segmentation clock and antero-posterior (A-P) polarity of somites revealed that the nine mutants can be compiled into two groups. In group 1, mutants exhibit defects in tailbud formation and PSM prepatterning, whereas A-P identity in the somites is defective in group 2 mutants. Three mutants (planlos, pll; schnelles ende, sne; samidare, sam) have characteristic phenotypes that are similar to those in zebrafish mutants affected in the Delta/Notch signaling pathway. The majority of mutants, however, exhibit somitic phenotypes distinct from those found in zebrafish, such as individually fused somites and irregular somite sizes. Thus, these Medaka mutants can be expected to provide clues to uncovering novel components essential for somitogenesis.

A subpopulation of bone marrow cells depleted by a novel antibody, anti-Liv8, is useful for cell therapy to repair damaged liver

We previously reported a new in vivo model named as "GFP/CCl(4) model" for monitoring the transdifferentiation of green fluorescent protein (GFP) positive bone marrow cell (BMC) into albumin-positive hepatocyte under the specific "niche" made by CCl(4) induced persistent liver damage, but the subpopulation which BMCs transdifferentiate into hepatocytes remains unknown. Here we developed a new monoclonal antibody, anti-Liv8, using mouse E 11.5 fetal liver as an antigen. Anti-Liv8 recognized both hematopoietic progenitor cells in fetal liver at E 11.5 and CD45-positive hematopoietic cells in adult bone marrow. We separated Liv8-positive and Liv8-negative cells and then transplanted these cells into a continuous liver damaged model. At 4 weeks after BMC transplantation, more efficient repopulation and transdifferentiation of BMC into hepatocytes were seen with Liv8-negative cells. These findings suggest that the subpopulation of Liv8-negative cells includes useful cells to perform cell therapy on repair damaged liver.

MKK7 couples stress signalling to G2/M cell-cycle progression and cellular senescence

During the development of multicellular organisms, concerted actions of molecular signalling networks determine whether cells undergo proliferation, differentiation, death or ageing. Here we show that genetic inactivation of the stress signalling kinase, MKK7, a direct activator of JNKs in mice, results in embryonic lethality and impaired proliferation of hepatocytes. Beginning at passage 4-5, mkk7(-/-) mouse embryonic fibroblasts (MEFs) display impaired proliferation, premature senescence and G2/M cell cycle arrest. Similarly, loss of c-Jun or expression of a c-JunAA mutant in which the JNK phosphorylation sites were replaced with alanine results in a G2/M cell-cycle block. The G2/M cell-cycle kinase CDC2 was identified as a target for the MKK7-JNK-c-Jun pathway. These data show that the MKK7-JNK-c-Jun signalling pathway couples developmental and environmental cues to CDC2 expression, G2/M cell cycle progression and cellular senescence in fibroblasts.

Stress induces mitochondria-mediated apoptosis independent of SAPK/JNK activation in embryonic stem cells

SAPK/JNK, which belongs to the family of mitogen-activated protein kinase (MAPK), is activated by many types of cellular stresses or extracellular signals and is involved in embryonic development, immune responses, and cell survival or apoptosis. However, the physiological roles of SAPK/JNK in the signaling of stress-induced apoptosis are still controversial. To evaluate the precise function, SAPK/JNK-inactivated mouse embryonic stem (ES) cells were generated by disrupting genes of the MAPK activators, SEK1 and MKK7. Although SAPK/JNK activation by various stresses was completely abolished in sek1(-/-) mkk7(-/-) ES cells, apoptotic responses including DNA fragmentation and caspase 3 activation still occurred normally, which displays a sharp contrast to apaf1(-/-) ES cells exhibiting profound defects in the mitochondria-dependent apoptosis. These normal apoptotic responses without SAPK/JNK activation were also observed in fibroblasts derived from sek1(-/-) mkk7(-/-) ES cells. Instead, interleukin-1 beta (IL-1 beta)-induced IL-6 gene expression was greatly suppressed in sek1(-/-) mkk7(-/-) fibroblasts. These results clearly show that SAPK/JNK activation is responsible for the inflammatory cytokine-induced gene expression but not essentially required for the mitochondria-dependent apoptosis at least in ES or fibroblast-like cells, which are prototypes of all cell lineages.

Dual Phosphorylation of Phosphoinositide 3-Kinase Adaptor Grb2-Associated Binder 2 Is Responsible for Superoxide Formation Synergistically Stimulated by Fcγ and Formyl-Methionyl-Leucyl-Phenylalanine Receptors in Differentiated THP-1 Cells

The class Ia phosphoinositide (PI) 3-kinase consisting of p110 catalytic and p85 regulatory subunits is activated by Tyr kinase-linked membrane receptors such as FcgammaRII through the association of p85 with the phosphorylated receptors or adaptors. The heterodimeric PI 3-kinase is also activated by G protein-coupled chemotactic fMLP receptors, and activation of the lipid kinase plays an important role in various immune responses, including superoxide formation in neutrophils. Although fMLP-induced superoxide formation is markedly enhanced in FcgammaRII-primed neutrophils, the molecular mechanisms remain poorly characterized. In this study, we identified two Tyr-phosphorylated proteins, c-Cbl (Casitas B-lineage lymphoma) and Grb2-associated binder 2 (Gab2), as PI 3-kinase adaptors that are Tyr phosphorylated upon the stimulation of FcgammaRII in differentiated neutrophil-like THP-1 cells. Interestingly, Gab2 was, but c-Cbl was not, further Ser/Thr phosphorylated by fMLP. Thus, the adaptor Gab2 appeared to be dually phosphorylated at the Ser/Thr and Tyr residues through the two different types of membrane receptors. The Ser/Thr phosphorylation of Gab2 required the activation of extracellular signal-regulated kinase, and fMLP receptor stimulation indeed activated extracellular signal-regulated kinase in the cells. Enhanced superoxide formation in response to Fcgamma and fMLP was markedly attenuated when the Gab2 Ser/Thr phosphorylation was inhibited. These results show the importance of the dual phosphorylation of PI 3-kinase adaptor Gab2 for the enhanced superoxide formation in neutrophil-type cells.

An In Vivo Model for Monitoring Trans-Differentiation of Bone Marrow Cells into Functional Hepatocytes

The plasticity of bone marrow cells (BMCs) remains controversial. The present study found that persistent injury induces efficient trans-differentiation of BMCs into functional hepatocytes. Mice with liver cirrhosis induced by carbon tetrachloride were injected with 1 x 10(5) non-treated green fluorescent protein (GFP)-positive BMCs via the tail vein. In these mice, transplanted GFP-positive BMCs efficiently migrated into the peri-portal area of liver lobules after one day, repopulating 25% of the recipient liver by 4 weeks. In contrast, no GFP-positive BMCs were detected following transplantation into control mice with undamaged livers. BMCs trans-differentiated into functional mature hepatocytes via immature hepatoblasts. Serum albumin levels were significantly elevated to compensate for chronic liver failure in BMC transplantation. These results reveal that recipient conditions and microenvironments represent key factors for successful cell therapy using BMCs.

Activation mechanism and physiological roles of stress-activated protein kinase/c-Jun NH2-terminal kinase in mammalian cells

Stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK), which belongs to the family of mitogen-activated protein kinase (MAPK), is activated by many types of cellular stress or extracellular signals. Recent studies, including the analysis with knockout cells and mice, have led towards understanding the molecular mechanism of stress-induced SAPK/JNK activation and the physiological roles of SAPK/JNK in embryonic development and immune responses. Two SAPK/JNK activators, SEK1 and MKK7, are required for full activation of SAPK/JNK, which responds to various stimuli in an all-or-none manner in mouse embryonic stem (ES) cells. SAPK/JNK activation plays essential roles in organogenesis during mouse development by regulating cell proliferation, survival or apoptosis and in immune responses by regulating cytokine gene expression. Furthermore, SAPK/JNK is involved in regulation of mRNA stabilization, cell migration, and cytoskeletal integrity. Thus, SAPK/JNK has a wide range of functions in mammalian cells.

Dentatorubral-pallidoluysian atrophy protein is phosphorylated by c-Jun NH2-terminal kinase

Dentatorubral-pallidoluysian atrophy (DRPLA) is a dominant-inherited neurodegenerative disease characterized by selective cell loss in particular neuronal pathways. This is caused by expansion of CAG repeats in the coding region of the DRPLA gene, and the extended polyglutamine tract (polyQ) confers a toxic activity. It is valuable to characterize disease gene products for elucidation of the mechanism underlying neuron death at specific anatomical areas of the brain. Here, we define the DRPLA protein as a phosphoprotein, and c-Jun NH(2)-terminal kinase (JNK) is one of the major factors involved in its phosphorylation. Endogenous DRPLA protein was serine-phosphorylated. Phosphorylation was demonstrated in a recombinant JNK activation system in vitro and also in overexpressing cells by transfection after the JNK activation with osmotic pressure. One of the phospho-acceptor sites for JNK appearing in the DRPLA sequence was indeed phosphorylated, which was confirmed by a specific antibody raised against the phosphopeptide. Kinetic studies in the JNK recombinant system showed that expanded polyQ slightly reduced the affinity of JNK to the protein. Thus, the abnormal DRPLA protein seems to be slowly phosphorylated in a certain condition of JNK activation in patients. It may delay a process that is essential in keeping neurons alive.

Different properties of SEK1 and MKK7 in dual phosphorylation of stress-induced activated protein kinase SAPK/JNK in embryonic stem cells

Stress-activated protein kinase/c-Jun NH(2)-terminal kinase (SAPK/JNK), belonging to the mitogen-activated protein kinase family, plays an important role in stress signaling. SAPK/JNK activation requires the phosphorylation of both Thr and Tyr residues in its Thr-Pro-Tyr motif, and SEK1 and MKK7 have been identified as the dual specificity kinases. In this study, we generated mkk7(-/-) mouse embryonic stem (ES) cells in addition to sek1(-/-) cells and compared the two kinases in terms of the activation and phosphorylation of JNK. Although SAPK/JNK activation by various stress signals was markedly impaired in both sek1(-/-) and mkk7(-/-) ES cells, there were striking differences in the dual phosphorylation profile. The severe impairment observed in mkk7(-/-) cells was accompanied by a loss of the Thr phosphorylation of JNK without marked reduction in its Tyr-phosphorylated level. On the other hand, Thr phosphorylation of JNK in sek1(-/-) cells was also attenuated in addition to a decreased level of its Tyr phosphorylation. Analysis in human embryonic kidney 293T cells transfected with a kinase-dead SEK1 or a Thr-Pro-Phe mutant of JNK1 revealed that SEK1-induced Tyr phosphorylation of JNK1 was followed by additional Thr phosphorylation by MKK7. Furthermore, SEK1 but not MKK7 was capable of binding to JNK1 in 293T cells. These results indicate that the Tyr and Thr residues of SAPK/JNK are sequentially phosphorylated by SEK1 and MKK7, respectively, in the stress-stimulated ES cells.

Weak agonist self-peptides promote selection and tuning of virus-specific T cells

Recent progress has begun to define the interactions and signaling pathways that are triggered during positive selection. To identify and further examine self-peptides that can mediate positive selection, we searched a protein-database to find peptides that have minimal homology with the viral peptide (p33) that activates a defined P14 transgenic TCR. We identified four peptides that could bind the restriction element H-2D(b) and induce proliferation of P14 transgenic splenocytes at high concentration. Two of the four peptides (DBM and RPP) were able to positively select the virus-specific TCR in fetal thymic organ culture but were unable to induce clonal deletion. Reverse-phase HPLC and mass spectrometry demonstrated that these peptides were presented by H-2D(b) molecules on thymic epithelial cell lines. We also examined whether the selecting ligands altered T cell responsiveness in vitro. DBM-selected T cells lost their ability to respond to the positively selecting ligand DBM, whereas RPP-selected T cells only retained their ability to respond to high concentrations of RPP. These results demonstrate that self-peptides that mediate positive selection can differentially "tune" the activation threshold of T cells and alter the functional repertoire of T cells.

Induction and activation of the transcription factor NFATc1 (NFAT2) integrate RANKL signaling in terminal differentiation of osteoclasts

Signaling by RANKL is essential for terminal differentiation of monocytes/macrophages into osteoclasts. The TRAF6 and c-Fos signaling pathways both play important roles downstream of RANKL. We show here that RANKL selectively induces NFATc1 expression via these two pathways. RANKL also evokes Ca(2+) oscillations that lead to calcineurin-mediated activation of NFATc1, and therefore triggers a sustained NFATc1-dependent transcriptional program during osteoclast differentiation. We also show that NFATc1-deficient embryonic stem cells fail to differentiate into osteoclasts in response to RANKL stimulation, and that ectopic expression of NFATc1 causes precursor cells to undergo efficient differentiation without RANKL signaling. Thus, NFATc1 may represent a master switch for regulating terminal differentiation of osteoclasts, functioning downstream of RANKL.

SEK1/MKK4-mediated SAPK/JNK signaling participates in embryonic hepatoblast proliferation via a pathway different from NF-kappaB-induced anti-apoptosis

Mice lacking the stress-signaling kinase SEK1 die from embryonic day 10.5 (E10.5) to E12.5. Although a defect in liver formation is accompanied with the embryonic lethality of sek1(-/-) mice, the mechanism of the liver defect has remained unknown. In the present study, we first produced a monoclonal antibody specifically recognizing murine hepatoblasts for the analysis of liver development and further investigated genetic interaction ofsek1 with tumor necrosis factor-alpha receptor 1 gene (tnfr1) and protooncogene c-jun, which are also responsible for liver formation and cell apoptosis. The defective liver formation in sek1(-/-) embryos was not protected by additionaltnfr1 mutation, which rescues the embryonic lethality of mice lacking NF-kappaB signaling components. There was a progressive increase in the hepatoblast cell numbers of wild-type embryos from E10.5 to E12.5. Instead, impaired hepatoblast proliferation was observed in sek1(-/-) livers from E10.5, though fetal liver-specific gene expression was normal. The impaired phenotype in sek1(-/-) livers was more severe than in c-jun(-/-) embryos, and sek1(-/-) c-jun(-/-) embryos died more rapidly before E8.5. The hepatoblast proliferation required no hematopoiesis, since liver development was not impaired in AML1(-/-) mice that lack hematopoietic functions. Stimulation of stress-activated protein kinase/c-Jun N-terminal kinase by hepatocyte growth factor was attenuated in sek1(-/-) livers. Thus, SEK1 appears to play a crucial role in hepatoblast proliferation and survival in a manner apparently different from NF-kappaB or c-Jun.

Possible involvement of IkappaB kinase 2 and MKK7 in osteoclastogenesis induced by receptor activator of nuclear factor kappaB ligand

Recent studies have revealed the essential role of the receptor activator of nuclear factor kappaB (NF-kappaB) ligand (RANKL) in osteoclast differentiation and activation. Adenovirus vector could efficiently transduce genes into RAW264.7 cells, which differentiate into osteoclast-like multinucleated cells in the presence of RANKL. The role of NF-kappaB and c-jun N-terminal kinase (JNK) activation in RANKL-induced osteoclast differentiation was investigated using an adenovirus vector carrying the dominant negative 1kappaB kinase 2 gene (AxIKK2DN) or dominant negative MKK7 gene (AxMKK7DN). IKK2DN and MKK7DN overexpression in RAW cells specifically suppressed the NF-kappaB activation and JNK activation in response to RANKL, respectively, without affecting other signaling pathways. Either inhibition of NF-kappaB or JNK pathways dose-dependently inhibited osteoclast formation induced by RANKL. These results suggest that both NF-kappaB and JNK activation are independently required for osteoclast differentiation.

Mild maternal undernutrition in the first half of ovine pregnancy influences placental morphology but not fetal Doppler flow velocity waveforms and fetal heart size

AIMS

We wanted to investigate whether experimental dietary manipulations during early pregnancy influence placental growth and subsequently the cardiovascular system as assessed non-invasively by ultrasonography in the sheep fetus.

METHODS

21 ewes bearing singletons of uniform age were randomly assigned for the first half of pregnancy to one of the following study groups: fed 100% of their nutritional requirements (i.e. controls), global reduction in total intake by 30% (i.e. 70% global) and reduction in protein intake by 30% (i.e. 70% protein).

RESULTS

Placentas from the 70% protein group had significantly more small placentomes, but significantly fewer large placentomes compared to the 70% global group. However, there were no significant differences between the three dietary groups for either the aortic or the umbilical Doppler velocimetry parameters and the fetal heart rate or heart size.

CONCLUSIONS

The present study shows that early mild maternal undernutrition produces subtle changes in cotelydonary weight. However, Doppler and echocardiographic parameters were not affected by these changes.

Activation of extracellular signal-regulated kinase by ultraviolet is mediated through Src-dependent epidermal growth factor receptor phosphorylation. Its implication in an anti-apoptotic function

Ultraviolet (UV) irradiation stimulates stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), which is a member of the mitogen-activated protein kinase (MAPK) superfamily and implicated in stress-induced apoptosis. UV also induces the activation of another MAPK member, extracellular signal-regulated kinase (ERK), which is typically involved in a growth-signaling cascade. However, the UV-induced signaling pathway leading to ERK activation, together with the physiological role, has remained unknown. Here we examined the molecular mechanism and physiological function of UV-induced ERK activation in human epidermoid carcinoma A431 cells that retain a high number of epidermal growth factor (EGF) receptors. UV-induced ERK activation was accompanied with the Tyr phosphorylation of EGF receptors, and both responses were completely abolished in the presence of a selective EGF receptor inhibitor (AG1478) or the Src inhibitor PP2 and by the expression of a kinase-dead Src mutant. On the other hand, SAPK/JNK activation by UV was partially inhibited by these inhibitors. UV stimulated Src activity in a manner similar to the ERK activation, but the Src activation was insensitive to AG1478. UV-induced cell apoptosis measured by DNA fragmentation and caspase 3 activation was enhanced by AG1478 and an ERK kinase inhibitor (U0126) but inhibited by EGF receptor stimulation by the agonist. These results indicate that UV-induced ERK activation, which provides a survival signal against stress-induced apoptosis, is mediated through Src-dependent Tyr phosphorylation of EGF receptors.

Visualisation and measurement of tracheal diameter in the sheep fetus: an ultrasound study with stereomicroscopic correlation

OBJECTIVE

There is no information on ultrasonographic visualisation of the upper airways in the sheep fetus, but this species permits to examine the accuracy of ultrasonography in measuring the inner tracheal diameter. This was the aim of our study.

METHODS

Transabdominal ultrasonography to visualise the trachea was attempted in 16 unsedated Welsh Mountain ewes with a singleton pregnancy at 70 (SD 2) days gestation (term 148 days). The ultrasonographically measured inner tracheal diameter was compared with the actual inner tracheal diameter obtained by stereomicroscopy post-mortem.

RESULTS

High-resolution ultrasonography permitted clear imaging of the fetal trachea in 87% (14/16) of the cases analysed. The ultrasound measurements were smaller than the corresponding stereomicroscopic measurements, the mean +/- SD difference between the measurements being 0.40 +/- 0.12 mm.

CONCLUSIONS

Improvements in ultrasound have led to increased interest in the assessment of the trachea in human fetuses. Our study in the ovine fetus at mid gestation shows that optimal views of the fetal trachea allowing accurate measurements can be obtained in almost all the cases.

WSX-1 is required for the initiation of Th1 responses and resistance to L. major infection

WSX-1 is a class I cytokine receptor with homology to the IL-12 receptors. The physiological role of WSX-1, which is expressed mainly in T cells, was investigated in gene-targeted WSX-1-deficient mice. IFN-gamma production was reduced in isolated WSX-1(-/-) T cells subjected to primary stimulation in vitro to induce Th1 differentiation but was normal in fully differentiated and activated WSX-1(-/-) Th1 cells that had received secondary stimulation. WSX-1(-/-) mice were remarkably susceptible to Leishmania major infection, showing impaired IFN-gamma production early in the infection. However, IFN-gamma production during the later phases of the infection was not impaired in the knockout. WSX-1(-/-) mice also showed poorly differentiated granulomas with dispersed accumulations of mononuclear cells when infected with bacillus Calmette-Guerin (BCG). Thus, WSX-1 is essential for the initial mounting of Th1 responses but dispensable for their maintenance.

The stress kinase mitogen-activated protein kinase kinase (MKK)7 is a negative regulator of antigen receptor and growth factor receptor-induced proliferation in hematopoietic cells

The dual specificity kinases mitogen-activated protein kinase (MAPK) kinase (MKK)7 and MKK4 are the only molecules known to directly activate the stress kinases stress-activated protein kinases (SAPKs)/c-Jun N-terminal kinases (JNKs) in response to environmental or mitogenic stimuli. To examine the physiological role of MKK7 in hematopoietic cells, we used a gene targeting strategy to mutate MKK7 in murine T and B cells and non-lymphoid mast cells. Loss of MKK7 in thymocytes and mature B cells results in hyperproliferation in response to growth factor and antigen receptor stimulation and increased thymic cellularity. Mutation of mkk7 in mast cells resulted in hyperproliferation in response to the cytokines interleukin (IL)-3 and stem cell factor (SCF). SAPK/JNK activation was completely abolished in the absence of MKK7, even though expression of MKK4 was strongly upregulated in mkk7(-/-) mast cell lines, and phosphorylation of MKK4 occurred normally in response to multiple stress stimuli. Loss of MKK7 did not affect activation of extracellular signal-regulated kinase (ERK)1/2 or p38 MAPK. mkk7(-/-) mast cells display reduced expression of JunB and the cell cycle inhibitor p16INK4a and upregulation of cyclinD1. Reexpression of p16INK4a in mkk7(-/-) mast cells abrogates the hyperproliferative response. Apoptotic responses to a variety of stimuli were not affected. Thus, MKK7 is an essential and specific regulator of stress-induced SAPK/JNK activation in mast cells and MKK7 negatively regulates growth factor and antigen receptor-driven proliferation in hematopoietic cells. These results indicate that the MKK7-regulated stress signaling pathway can function as negative regulator of cell growth in multiple hematopoietic lineages.

Impaired synergistic activation of stress-activated protein kinase SAPK/JNK in mouse embryonic stem cells lacking SEK1/MKK4: different contribution of SEK2/MKK7 isoforms to the synergistic activation

Stress-activated protein kinase/c-Jun NH(2)-terminal kinase (SAPK/JNK), which is a member of the mitogen-activated protein kinase (MAPK) family, plays an important role in a stress-induced signaling cascade. SAPK/JNK activation requires the phosphorylation of Thr and Tyr residues in its Thr-Pro-Tyr motif, and SEK1 (MKK4) and MKK7 (SEK2) have been identified as the upstream MAPK kinases. Here we examined the activation and phosphorylation sites of SAPK/JNK and differentiated the contribution of SEK1 and MKK7alpha1, -gamma1, and -gamma2 isoforms to the MAPK activation. In SEK1-deficient mouse embryonic stem cells, stress-induced SAPK/JNK activation was markedly impaired, and this defect was accompanied with a decreased level of the Tyr phosphorylation. Analysis in HeLa cells co-transfected with the two MAPK kinases revealed that the Thr and Tyr of SAPK/JNK were independently phosphorylated in response to heat shock by MKK7gamma1 and SEK1, respectively. However, MKK7alpha1 failed to phosphorylate the Thr of SAPK/JNK unless its Tyr residue was phosphorylated by SEK1. In contrast, MKK7gamma2 had the ability to phosphorylate both Thr and Tyr residues. In all cases, the dual phosphorylation of the Thr and Tyr residues was essentially required for the full activation of SAPK/JNK. These data provide the first evidence that synergistic activation of SAPK/JNK requires both phosphorylation at the Thr and Tyr residues in living cells and that the preference for the Thr and Tyr phosphorylation was different among the members of MAPK kinases.

Dietary restriction in pregnant rats causes gender-related hypertension and vascular dysfunction in offspring

We have investigated the effects of moderate global undernutrition during gestation in the rat on the blood pressure of male and female offspring, and on the development of systemic vascular function. Pregnant Wistar rats were nutritionally restricted (R) by feeding with 70% of the normal gestation-matched dietary intake from 0 to 18 days gestation.R offspring were growth retarded at birth but of similar weight to controls (C) at 20 days. Systolic and/or diastolic and mean arterial blood pressures, measured directly by femoral artery catheter, were elevated from 60 days onward in male R offspring (mean arterial pressure: day 60, P < 0.01; day 100, P < 0.05; day 200, P < 0.005, R vs. C), and from 100 days onward in female R offspring (mean arterial pressure day 100 and day 200, P < 0.05; R vs. C). Maximal constriction to phenylephrine (PE) (P < 0.05) and to noradrenaline (NA) (P < 0.05) was reduced in isolated femoral arteries of day 20 R pups. These differences did not persist into adulthood. In male adult R offspring (200 days), maximal vasoconstriction to the thromboxane A2 mimetic, U46619 (P < 0.05) and sensitivity to potassium (P < 0.01) were enhanced. Moderate maternal undernutrition in rat gestation adversely affects cardiovascular function in the offspring. These abnormalities increase with age and are more pronounced in males.

Effects of undernutrition in early pregnancy on systemic small artery function in late-gestation fetal sheep

OBJECTIVE

The aim of this study was to investigate functional development of small arteries from the skeletal circulation of fetal sheep and to determine whether maternal undernutrition affects responses to vasoconstrictive and vasodilatory agonists in arteries from the late-gestation fetus.

STUDY DESIGN

We investigated vasoconstrictive and vasodilatory responses of isolated small (approximately 300 microm) arteries from the femoral vascular bed of fetal sheep and from late-gestation pregnant ewes. Ewes were fed either 100% of the nutritional requirement throughout pregnancy (control group) or a restricted diet of 85% or 50% of the nutritional requirement for the first 70 days of pregnancy. For the remainder of pregnancy all ewes were fed the complete diet.

RESULTS

Among control group animals vasoconstriction in response to norepinephrine was well developed in fetuses at 0.6 and 0.9 gestation with respect to that in the ewes. When expressed as a percentage of the response to 125-mmol/L potassium (to correct for differences in vessel size and muscle mass), maximum constriction in response to norepinephrine was greater in fetal vessels from 0.9 gestation than in either those at 0.6 gestation or those of the ewes. Endothelium-dependent vasorelaxation responses to acetylcholine and bradykinin were also well developed in fetuses at 0.6 and 0.9 gestation and were similar to those in the ewes. In fetuses at 0.9 gestation the 50% nutritional restriction of the ewe led to blunted endothelium-dependent vasodilatation in response to acetylcholine and blunted endothelium-independent vasodilatation in response to sodium nitroprusside. Responses in the fetuses at 0.9 gestation in which the ewes were fed a restricted diet of 85% were normal.

CONCLUSION

This study shows that from midgestation onward small arteries from the skeletal circulation of the fetal sheep have the functional capacity to respond to norepinephrine and endothelium-dependent vasodilators (eg, acetylcholine and bradykinin). The blunted responses to acetylcholine and sodium nitroprusside in the fetuses at 0.9 gestation among the group of dietarily restricted ewes (restricted diet of 50% group) were indicative of impaired vascular smooth muscle sensitivity to nitric oxide. This defect may contribute to the development of hypertension in later life.

Effect of NO, phenylephrine, and hypoxemia on ductus venosus diameter in fetal sheep

To study the regulation of the ductus venosus (DV) inlet in vivo, we measured the effect of vasoactive substances and hypoxemia on its diameter in nine fetal sheep in utero at 0.9 gestation under ketamine-diazepam anesthesia. Catheters were inserted into an umbilical vein and a fetal common carotid artery, and a flowmeter was placed around the umbilical veins. Ultrasound measurements of the diameter of the fetal DV during normoxic baseline conditions [fetal arterial PO(2) (PaO(2)) 24 mmHg] were compared with measurements during infusion of sodium nitroprusside (SNP; 1.3, 2.6, and 6.5 microg. kg(-1). min(-1)) or the alpha(1)-adrenergic agonist phenylephrine (6.5 microg. kg(-1). min(-1)) into the umbilical vein or during hypoxemia (fetal Pa(O(2)) reduced to 10 mmHg). SNP increased the DV inlet diameter by 23%, but phenylephrine had no effect. Hypoxemia caused a 61% increase of the inlet diameter and a distension of the entire vessel. We conclude that the DV inlet is tonically constricted, because nitric oxide dilates it but an alpha(1)-adrenergic agonist does not potentiate constriction. Hypoxemia causes a marked distension of the entire DV.

Negative regulation of lymphocyte activation and autoimmunity by the molecular adaptor Cbl-b

The signalling thresholds of antigen receptors and co-stimulatory receptors determine immunity or tolerance to self molecules. Changes in co-stimulatory pathways can lead to enhanced activation of lymphocytes and autoimmunity, or the induction of clonal anergy. The molecular mechanisms that maintain immunotolerance in vivo and integrate co-stimulatory signals with antigen receptor signals in T and B lymphocytes are poorly understood. Members of the Cbl/Sli family of molecular adaptors function downstream from growth factor and antigen receptors. Here we show that gene-targeted mice lacking the adaptor Cbl-b develop spontaneous autoimmunity characterized by auto-antibody production, infiltration of activated T and B lymphocytes into multiple organs, and parenchymal damage. Resting cbl-b(-/-) lymphocytes hyperproliferate upon antigen receptor stimulation, and cbl-b(-/-) T cells display specific hyperproduction of the T-cell growth factor interleukin-2, but not interferon-gamma or tumour necrosis factor-alpha. Mutation of Cbl-b uncouples T-cell proliferation, interleukin-2 production and phosphorylation of the GDP/GTP exchange factor Vav1 from the requirement for CD28 co-stimulation. Cbl-b is thus a key regulator of activation thresholds in mature lymphocytes and immunological tolerance and autoimmunity.

The action of a novel vitamin D3 analogue, OCT, on immunomodulatory function of keratinocytes and lymphocytes

Topical vitamin D3 has relatively recently been introduced for the treatment of psoriasis. Synthetic vitamin D3 analogues with a high potential for inducing differentiation of cells, but with a low hypercalcemic effect have recently been developed. One such synthetic analogue of 1,25-dihydroxyvitamin D3 (calcitriol), 22-oxacalcitriol (OCT), is a novel agent for the topical treatment of psoriasis. The activity of OCT in vitro was investigated and compared with that of a series of vitamin D3 analogues as to their ability to inhibit murine T lymphocyte proliferation stimulated by con-A, to suppress IL-6 and IL-8 production by keratinocytes stimulated with IL-1alpha and TNFalpha, and to inhibit AP-1- and NFkappaB-dependent reporter gene expression. OCT inhibited the proliferation of lymphocytes and suppressed IL-8 and IL-6 production by keratinocytes to the same extent as the other vitamin D3 analogues. It also inhibited AP-1- and NFkappaB-controlled luciferase activity to the same extent as the other vitamin D3 analogues, which demonstrates its mechanism of action in the suppression of inflammatory processes.

Mechanisms of noradrenaline-induced vasorelaxation in isolated femoral arteries of the neonatal rat

Isolated arteries from the femoral circulation of Wistar rats mounted on a small vessel myograph demonstrated age related tension development to noradrenaline (NA, 1 x 10(-8) - 5 x 10(-5) M) day 20 greater than day 10 (P<0.005); day 100 greater than day 20 (P<0.001) and depolarizing potassium (125 mM) buffer day 20 greater than day 10 (P<0.001). NA evoked dilatation in femoral arteries from neonatal rats (10 days) when added to unstimulated vessels or to those preconstricted with the thromboxane mimetic, U46619. Relaxation to NA was inhibited by L-NAME (0.1 mM) (P<0.001), endothelial removal (P<0.001) and the alpha2-adrenoceptor antagonist, yohimbine (0.1 microM) (P<0.001). Alpha1- or beta-adrenoceptor antagonism was without effect. Relaxation was evoked in femoral arteries of the 10-day-old rats by the alpha2-adrenoceptor agonist UK14304 (1 x 10(-8) - 5 x 10(-5) M). This relaxation was also abolished by L-NAME (0.1 mM) (P<0.001) or endothelial removal (P<0.001). Alpha2-adrenoceptor-mediated vasorelaxation was the predominant response to NA stimulation in femoral arteries of the neonatal rat. These responses were endothelium-dependent and were NO-mediated.

Goat fetuses disconnected from the placenta, but reconnected to an artificial placenta, display intermittent breathing movements

To investigate whether placental factors are involved in the intermittent breathing movements in goat fetuses, we assessed electrocortical activity (ECoA) and tracheal pressure in 5 fetuses (124-135 days) separated from the placenta and connected for 48 h to an extrauterine fetal incubation system that provided umbilical arteriovenous extracorporeal membrane oxygenation. The fetal physiological condition on this system was almost the same as that in utero for at least 48 h after the preparation. All fetuses showed intermittent low-voltage ECoA and breathing movements. The breathing movements occurred almost exclusively during periods of low- voltage ECoA. The proportions of time spent in low-voltage ECoA and breathing movements were 48-57% and 46-56%, respectively. In conclusion, breathing movements of fetuses on the extrauterine incubation system were episodic, suggesting that intermittent breathing movements are intrinsic to fetuses, independent of placenta-derived factors.

Defective liver formation and liver cell apoptosis in mice lacking the stress signaling kinase SEK1/MKK4

The stress signaling kinase SEK1/MKK4 is a direct activator of stress-activated protein kinases (SAPKs; also called Jun-N-terminal kinases, JNKs) in response to a variety of cellular stresses, such as changes in osmolarity, metabolic poisons, DNA damage, heat shock or inflammatory cytokines. We have disrupted the sek1 gene in mice using homologous recombination. Sek1(−/−)embryos display severe anemia and die between embryonic day 10.5 (E10.5) and E12.5. Haematopoiesis from yolk sac precursors and vasculogenesis are normal in sek1(−/−)embryos. However, hepatogenesis and liver formation were severely impaired in the mutant embryos and E11.5 and E12.5 sek1(−/−)embryos had greatly reduced numbers of parenchymal hepatocytes. Whereas formation of the primordial liver from the visceral endoderm appeared normal, sek1(−/−) liver cells underwent massive apoptosis. These results provide the first genetic link between stress-responsive kinases and organogenesis in mammals and indicate that SEK1 provides a crucial and specific survival signal for hepatocytes.

Activation of c-Jun N-terminal kinase (JNK) by lysophosphatidic acid in Swiss 3T3 fibroblasts

Lysophosphatidic acid (LPA) induced activation of c-Jun N-terminal kinase (JNK) in Swiss 3T3 fibroblasts. This activation reached the maximum at 20 min and required a high concentration of LPA with an EC50 value of approximately 3 microg/ml. LPA-induced activation of JNK was not suppressed by prior treatment of the cells with pertussis toxin, whereas it was completely blocked by suramin, a non-selective inhibitor of ligand-receptor interactions. The kinetics and concentration-dependency of LPA-induced JNK activation were in sharp contrast with those of LPA-induced extracellular signal-regulated kinase (ERK) activation, which reached the maximum within 3 min and occurred with an EC50 of 0.1 microg/ml. The ERK activation was susceptible to pertussis toxin, whereas it was not inhibited by suramin. These results indicate that the signal transduction pathways of LPA-induced JNK and ERK activations are distinct. Thus, this is the first report showing that LPA induces not only ERK activation but also JNK activation, which may be responsible for the induction of DNA synthesis in LPA-stimulated Swiss 3T3 fibroblasts.

Impaired TCR-mediated apoptosis and Bcl-XL expression in T cells lacking the stress kinase activator SEK1/MKK4

The dual specificity kinase SEK1 (MKK4) is a direct activator of stress-activated protein kinases (SAPK/JNK) in response to environmental stresses or mitogenic factors. We show in Sek1(-/-)Rag(-/-) chimeric mice that a Sek1 null mutation augments the susceptibility of peripheral T cells to TCR/CD3 religation-induced apoptosis. Sek1(-/-) T cells failed to induce expression of the death suppressor Bcl-XL in response to Ag receptor activation. The Sek1 mutation did not alter the induction of apoptosis in response to etoposide, cisplatinum, Adriamycin, and gamma-irradiation. Moreover, we show that CD3epsilon activation alone leads to SEK1 activation in Sek1(+/+) T cells. These results suggest that SEK1 transduces cellular survival signals during T cell stimulation.

Impaired TCR-Mediated Apoptosis and Bcl-XL Expression in T Cells Lacking the Stress Kinase Activator SEK1/MKK4

The dual specificity kinase SEK1 (MKK4) is a direct activator of stress-activated protein kinases (SAPK/JNK) in response to environmental stresses or mitogenic factors. We show in Sek1−/−Rag−/− chimeric mice that a Sek1 null mutation augments the susceptibility of peripheral T cells to TCR/CD3 religation-induced apoptosis. Sek1−/− T cells failed to induce expression of the death suppressor Bcl-XL in response to Ag receptor activation. The Sek1 mutation did not alter the induction of apoptosis in response to etoposide, cisplatinum, Adriamycin, and γ-irradiation. Moreover, we show that CD3ε activation alone leads to SEK1 activation in Sek1+/+ T cells. These results suggest that SEK1 transduces cellular survival signals during T cell stimulation.

Molecular mechanism of human CD38 gene expression by retinoic acid. Identification of retinoic acid response element in the first intron

CD38 is a nonlineage-restricted type II transmembrane glycoprotein possessing ecto-NAD+ glycohydrolase activity. Because of its unique expression pattern in lymphocyte differentiation, it appears to function as an immunoregulatory molecule. We previously reported that CD38 was specifically induced by all-trans-retinoic acid (RA) in human promyelocytic leukemia HL-60 cells. Here we studied the molecular mechanism of the RA-dependent induction of human CD38. The expression of CD38 mRNA by RA appeared to be caused by the transcriptional stimulation of the gene, since it was blocked by an RNA synthesis inhibitor, but not by a protein synthesis inhibitor. In search of the RA response element (RARE) possibly present in human CD38 gene promoter, we isolated and sequenced the genomic DNA covering the 5'-flanking region, exon 1, and partial intron 1. Transient transfection experiments revealed that the responsiveness to RA was conferred through an RARE consisting of two direct repeat TGACCT-like hexamer motifs with a 5-nucleotide spacer, which was located in the first intron rather than the 5'-flanking region of the CD38 gene. This RARE interacted with heterodimer composed of RA receptor and retinoid X receptor in vitro. Thus, the RA-induced expression of the human CD38 gene was demonstrated to be mediated through the RARE located in the first intron.

Upper cervical myelopathy associated with low CSF pressure: a complication of ventriculoperitoneal shunt

A patient who had undergone ventriculoperitoneal shunting developed upper cervical myelopathy. His CSF pressure was markedly low, and deformation of the spinal cord and shrinkage of the subarachnoid space at the upper cervical level were found in radiologic examinations. Ligation of the shunt tube resulted in almost complete recovery. The effect of excessive drainage may have caused the abnormalities.