Observation of Midgap States in GaN with Optical-Isothermal Capacitance Transient Spectroscopy

Optical-isothermal capacitance transient spectroscopy (O-ICTS) was used to distinguish the deep levels which occur in unintentionally doped n-type GaN by means of their characteristic optical cross section. GaN grown by metalorganic vapor phase epitaxy (MOVPE) and hydride vapor phase epitaxy (HVPE) were compared. Correspondence between optical and thermal emission characteristics of previously discovered levels, E2 (∼Ec-0.55 eV) and E4 (∼EC-1.0 eV), were clearly determined by observing their sequential appearance in the ICTS spectra. Whether by thermal or optical stimulation, the emission from E4 was found to be broad in nature; it is consequently believed to involve a defect. The total measured concentration of deep levels, including a prominent level which photoionizes in the range 2.5 to 3.0 eV below the conduction band, is greater in the GaN grown by MOVPE than by HVPE that was tested.

Generation of induced pluripotent stem cells in rabbits: potential experimental models for human regenerative medicine

Human induced pluripotent stem (iPS) cells have the potential to establish a new field of promising regenerative medicine. Therefore, the safety and the efficiency of iPS-derived cells must be tested rigorously using appropriate animal models before human trials can commence. Here, we report the establishment of rabbit iPS cells as the first human-type iPS cells generated from a small laboratory animal species. Using lentiviral vectors, four human reprogramming genes (c-MYC, KLF4, SOX2, and OCT3/4) were introduced successfully into adult rabbit liver and stomach cells. The resulting rabbit iPS cells closely resembled human iPS cells; they formed flattened colonies with sharp edges and proliferated indefinitely in the presence of basic FGF. They expressed the endogenous pluripotency markers c-MYC, KLF4, SOX2, OCT3/4, and NANOG, whereas the introduced human genes were completely silenced. Using in vitro differentiating conditions, rabbit iPS cells readily differentiated into ectoderm, mesoderm, and endoderm. They also formed teratomas containing a variety of tissues of all three germ layers in immunodeficient mice. Thus, the rabbit iPS cells fulfilled all of the requirements for the acquisition of the fully reprogrammed state, showing high similarity to their embryonic stem cell counterparts we generated recently. However, their global gene expression analysis revealed a slight but rigid difference between these two types of rabbit pluripotent stem cells. The rabbit model should enable us to compare iPS cells and embryonic stem cells under the same standardized conditions in evaluating their ultimate feasibility for pluripotent cell-based regenerative medicine in humans.

[Sarcomatoid carcinoma of the thymus which caused acute epicarditis]

Thymic carcinoma is rare. Particularly sarcomatoid carcinoma of the thymus is a very rare disease it has been reported in only 15 patients to date. The prognosis is very poor and diagnosis and treatment have not yet been established. We report a case of 63-year-old man who was initially diagnosed with acute pericarditis and was finally found to be sarcomatoid carcinoma of the thymus. He underwent surgery and the tumor was completely resected. However, 6 months after surgery, local recurrence was noted. The patient was treated by radiotherapy followed by paclitaxel monotherapy. Partial remission was achieved transiently with paclitaxel, but the tumor again recurred. He died 33 months after surgery. The possibility of diseases like this tumor must be kept in mind for a patient with chest symptoms. Paclitaxel monotherapy is likely to be effective in treating sarcomatoid carcinoma of the thymus.

LKB1 suppresses p21-activated kinase-1 (PAK1) by phosphorylation of Thr109 in the p21-binding domain

The serine/threonine protein kinase LKB1 is a tumor suppressor gene mutated in Peutz-Jeghers syndrome patients. The mutations are found also in several types of sporadic cancer. Although LKB1 is implicated in suppression of cell growth and metastasis, the detailed mechanisms have not yet been elucidated. In this study, we investigated the effect of LKB1 on cell motility, whose acquisition occurs in early metastasis. The knockdown of LKB1 enhanced cell migration and PAK1 activity in human colon cancer HCT116 cells, whereas forced expression of LKB1 in Lkb1-null mouse embryonic fibroblasts suppressed PAK1 activity and PAK1-mediated cell migration simultaneously. Notably, LKB1 directly phosphorylated PAK1 at Thr(109) in the p21-binding domain in vitro. The phosphomimetic T109E mutant showed significantly lower protein kinase activity than wild-type PAK1, suggesting that the phosphorylation at Thr(109) by LKB1 was responsible for suppression of PAK1. Consistently, the nonphosphorylatable T109A mutant was resistant to suppression by LKB1. Furthermore, we found that PAK1 was activated in the hepatocellular carcinomas and the precancerous liver lesions of Lkb1(+/-) mice. Taken together, these results suggest that PAK1 is a direct downstream target of LKB1 and plays an essential role in LKB1-induced suppression of cell migration.

CDX transcription factors positively regulate expression of solute carrier family 5, member 8 in the colonic epithelium

BACKGROUND & AIMS

Caudal-related homeodomain transcription factors CDX1 and CDX2 regulate gut development and differentiation of intestinal epithelial cells; they are candidate tumor suppressors of colorectal carcinomas. Because the functions of CDX1 and CDX2 in the colonic epithelium are not fully understood, we sought to identify genes that they target.

METHODS

We conducted a chromatin immunoprecipitation (ChIP) screen to identify genes that bind the CDX transcription factors. Expression of target genes was analyzed in colon cells and tissues from Cdx1(-/-), Cdx2(+/-), Apc(+/Delta716), and wild-type (control) mice.

RESULTS

Using the ChIP screen, we identified solute carrier family 5, member 8 (SLC5A8, also known as SMCT1) as a direct target of CDX1 and CDX2. CDX transcription factors bind to the promoter region of SLC5A8 and transactivate SLC5A8 reporter constructs. Overexpression of Cdx1 or Cdx2 in human colon cancer cell lines induced expression of endogenous SLC5A8, whereas CDX1 and CDX2 knockdowns reduced its level. Consistently, Slc5a8 expression was significantly reduced in colons of Cdx1(-/-) or Cdx2(+/-) mice compared with wild-type mice. Slc5a8 levels were also reduced in colonic adenomatous polyps and hamartomas from Apc(+/Delta716) and Cdx2(+/-) mutant mice, respectively, compared with adjacent normal colon tissues.

CONCLUSIONS

CDX1 and CDX2 bind the promoter region of SLC5A8 and up-regulate its expression in cultured cells and in colonic epithelium. SLC5A8 transports monocarboxylates such as pyruvate, lactate, and butyrate; CDX1 and CDX2 might therefore regulate the uptake of these substances in the colon.

The role of stromal stem cells in tissue regeneration and wound repair

The process of wound repair in epithelium-lined organs of mammals is complex and is influenced by numerous secreted factors including cytokines, growth factors, and chemokines. However, the cellular organizers of this process are still not understood. Recent studies of tissue regeneration in organisms with simpler development have uncovered details about the activity of stem cells in the mesenchyme (the blastema) during this process. These blastemal cells are well positioned to interpret cues from the environment and to execute decisions about the direction of wound repair. In mammalian wounds, stromal stem cells appear to be positioned to perform functions similar to those of blastemal cells, including communication with both the overlying epithelium and the inflammatory cells in the mesenchyme.

Hepatocellular carcinoma development induced by conditional beta-catenin activation in Lkb1+/- mice

The development of hepatocellular carcinomas (HCC) appears to be a multistep process that takes several decades in humans. However, the identities of specific gene alterations and their contribution to HCC pathogenesis remain poorly understood. We previously reported that Lkb1(+/-) mice spontaneously develop multiple hepatic nodular foci (NdFc) followed by HCC, and that the conditional activation of beta-catenin in Catnb(lox(ex3)) mouse livers alone does not cause tumor formation. We show here that the conditional activation of beta-catenin accelerates HCC development in Catnb(+/lox(ex3))Lkb1(+/-) compound mutant mice, affecting displastic hepatocytes in NdFc that suffered LOH at the Lkb1 locus. We further show that beta-catnin activation provides HCC with a growth advantage as well as transplantability. These results suggest that the loss of Lkb1 contributes to the formation of dysplastic NdFc, and that Wnt signaling activation is involved in ensuing progression toward HCC. A combination of these sequential changes can be a practical model for a subset of human HCC.

T-box 21 transcription factor is responsible for distorted T(H)2 differentiation in human peripheral CD4+ T cells

BACKGROUND

Regardless of T(H)1/T(H)2 theory, CD4(+) T cells of patients with allergic asthma, a typical T(H)2 disease, and those of healthy subjects expressed equivalent levels of IFN-gamma, even though T(H)2 cytokines were significantly upregulated in asthmatic patients.

OBJECTIVE

The mechanisms underlying distorted T(H)2 cell polarization in human T cells were elucidated.

METHODS

Cytokine-producing activity and the expression of T(H)1/T(H)2-specific transcription factors in naïve, T(H)1/T(H)2, or both CD4(+) T cells derived from human peripheral and cord blood were comparatively analyzed. The mechanisms of the differential expression of T-box 21 transcription factor (T-bet) in the cells were assessed by determining the chromatin accessibility at the TBX21 gene. The functional roles of T-bet and other transcription factors in human T(H)1/T(H)2 differentiation were further investigated.

RESULTS

T(H)2 cells derived from naive CD4(+) T cells in peripheral blood but not in cord blood produced IFN-gamma. T-bet was expressed in peripheral, but not cord blood, resting naive T cells. Consistently, the accessibility at the proximal TBX21 gene promoter in peripheral naive T cells was higher than that in cord blood naive T cells. IFN-gamma-producing activity was induced in T(H)2-differentiated cord blood T cells by means of ectopic expression of T-bet. In addition, a reduction of T-bet in peripheral T cells suppressed IFN-gamma production. T-bet not only upregulated IFN-gamma but also downregulated IL-4 and IL-13 gene transcription, independently of the modification of T(H)1/T(H)2 balance.

CONCLUSION

The expression of T-bet at a naive stage is crucial for the development of IFN-gamma-producing T cells in human peripheral blood, even in T(H)2-related diseases.

Diffuse-type gastric carcinoma: progression, angiogenesis, and transforming growth factor beta signaling

Background

Diffuse-type gastric carcinoma is a cancer with poor prognosis that has high levels of transforming growth factor β (TGF-β) expression and thick stromal fibrosis. However, the association of TGF-β signaling with diffuse-type gastric carcinoma has not been investigated in detail.

Methods

We used a lentiviral infection system to express a dominant-negative TGF-β type II receptor (dnTβRII) or green fluorescent protein (GFP) as a control in the diffuse-type gastric carcinoma cell lines, OCUM-2MLN and OCUM-12. These infected cells and the corresponding parental control cells were subcutaneously or orthotopically injected into nude mice. Angiogenesis was inhibited by infecting cells with a lentivirus carrying the gene for angiogenic inhibitor thrombospondin-1 or by injecting mice intraperitoneally with the small-molecule angiogenic inhibitor sorafenib or with anti-vascular endothelial growth factor (VEGF) neutralizing antibody (six or eight mice per group). Expression of phospho-Smad2 and thrombospondin-1 was investigated immunologically in human gastric carcinoma tissues from 102 patients. All statistical tests were two-sided.

Results

Expression of dnTβRII into OCUM-2MLN cells did not affect their proliferation in vitro, but it accelerated the growth of subcutaneously or orthotopically transplanted tumors in vivo (eg, for mean volume of subcutaneous tumors on day 10 relative to that on day 0: dnTβRII tumors = 3.49 and GFP tumors = 2.46, difference = 1.02, 95% confidence interval [CI] = 0.21 to 1.84; P = .003). The tumors expressing dnTβRII had higher levels of angiogenesis than those expressing GFP because of decreased thrombospondin-1 production. Similar results were obtained with OCUM-12 cells. Expression of thrombospondin-1 in the dnTβRII tumor or treatment with sorafenib or anti-VEGF antibody reduced tumor growth, whereas knockdown of thrombospondin-1 expression resulted in more accelerated growth of OCUM-2MLN tumors than of GFP tumors (eg, mean tumor volumes on day 14 relative to those on day 0: thrombospondin-1–knockdown tumors = 4.91 and GFP tumors = 3.79, difference = 1.12, 95% CI = 0.80 to 1.44; P < .001). Positive association between phosphorylated Smad2 and thrombospondin-1 immunostaining was observed in human gastric carcinoma tissues.

Conclusions

Disruption of TGF-β signaling in diffuse-type gastric carcinoma models appeared to accelerate tumor growth, apparently through increased tumor angiogenesis that was induced by decreased expression of thrombospondin-1.

Retronectin enhances lentivirus-mediated gene delivery into hematopoietic progenitor cells

Genetic modification of hematopoietic stem cells holds great promise in the treatment of hematopoietic disorders. However, clinical application of gene delivery has been limited, in part, by low gene transfer efficiency. To overcome this problem, we investigated the effect of retronectin (RN) on lentiviral-mediated gene delivery into hematopoietic progenitor cells (HPCs) derived from bone marrow both in vitro and in vivo. RN has been shown to enhance transduction by promoting colocalization of lentivirus and target cells. We found that RN enhanced lentiviral transfer of the VENUS transgene into cultured c-Kit(+) Lin(-) HPCs. As a complementary approach, in vivo gene delivery was performed by subjecting mice to intra-bone marrow injection of lentivirus or a mixture of RN and lentivirus. We found that co-injection with RN increased the number of VENUS-expressing c-Kit(+) Lin(-) HPCs in bone marrow by 2-fold. Further analysis of VENUS expression in colony-forming cells from the bone marrow of these animals revealed that RN increased gene delivery among these cells by 4-fold. In conclusion, RN is effective in enhancing lentivirus-mediated gene delivery into HPCs.

Abnormal DNA methyltransferase expression in mouse germline stem cells results in spermatogenic defects

Although spermatogonial stem cells (SSCs) are committed to spermatogenesis, they may also convert to an embryonic stem cell-like pluripotent state at a low frequency. Because changes in DNA methylation patterns are associated with this conversion, we examined the effect of manipulating DNA methyltransferase (Dnmt) expression on the fate of cultured SSCs, germline stem (GS) cells. Dnmt1 knockdown induced apoptosis in GS cells, which was attenuated by the loss of Trp53. In contrast, GS cells proliferated normally in vitro after Dnmt3a/Dnmt3b ablation or during Dnmt3l overexpression. However, Dnmt3a/Dnmt3b double-mutant cells showed hypomethylation in the SineB1 repetitive sequence, and Dnmt3l-overexpressing cells showed hypermethylation in major and minor satellite sequences; neither cell type formed teratomas and completed spermatogenesis following transplantation into the seminiferous tubules. Although genetic manipulation did not increase the conversion of GS cells to a pluripotent state, these results underscore the important role of DNMTs in survival and spermatogenic differentiation in SSCs.

Stable embryonic stem cell lines in rabbits: potential small animal models for human research

Although embryonic stem (ES) cell lines derived from mice and primates are used extensively, the development of such lines from other mammals is extremely difficult because of their rapid decline in proliferation potential and pluripotency after several passages. This study describes the establishment of rabbit ES cell lines with indefinite proliferation potential. It was found that the feeder cell density determines the fate of rabbit ES cells, and that maximum proliferation potential was obtained when they were cultured on a feeder cell density of one-sixth of the density at confluency. Higher and lower densities of feeder cells induced ES cell differentiation or division arrest. Under optimized conditions, rabbit ES cells were passaged 50 times, after which they still possessed high telomerase activity. This culture system enabled efficient gene transduction and clonal expansion from single cells. During culture, rabbit ES cells exhibited flattened monolayer cell colonies, as reported for monkey and human ES cells, and expressed pluripotency markers. Embryoid bodies and teratomas formed readily in vitro and in vivo respectively. These ES cell lines can be safely cryopreserved for later use. Thus, rabbit ES cells can be added to the list of stable mammalian ES cells, enabling the rabbit to be used as a small animal model for the study of human cell transplantation therapy.

Expression of osterix inhibits bone morphogenetic protein-induced chondrogenic differentiation of mesenchymal progenitor cells

Osteoblasts and chondrocytes arise from common bipotential mesenchymal progenitor cells. Although the differentiation of these two cell lineages can be induced by treatment with bone morphogenetic proteins (BMPs), the responses of mesenchymal progenitors to BMP differ from cell line to cell line. Here we demonstrate that C3H/10T1/2 cells preferred chondrogenic differentiation, primary bone marrow stroma cells (MSCs) tended to convert to osteoblasts, and ST-2 cells differentiated into both the osteoblastic and chondrocytic lineages simultaneously, suggesting that a molecular switch functions to select cell fate. Osterix, the secondary master regulator of osteoblastogenesis, was induced by BMP at high and low levels in MSCs and ST-2 cells, respectively; in contrast, C3H/10T1/2 cells demonstrated only faint expression. As osterix has been suggested as a negative regulator of chondrogenesis, we hypothesized that the intense chondrocyte differentiation of C3H/10T1/2 cells may have resulted from an absence of osterix. We therefore restored osterix gene expression in C3H/10T1/2 cells using an adenovirus vector. Following BMP treatment, infection with an osterix-encoding virus dramatically inhibited the chondrocytic differentiation of C3H/10T1/2 cells, resulting instead in prominent osteoblast differentiation. These results indicate the chondrogenic potential of C3H/10T1/2 cells was abrogated by osterix expression. Chondrocyte differentiation of MSCs, however, was not enhanced by silencing the osterix gene using lentivirus-mediated shRNA, despite successful suppression of osteoblast differentiation. These results suggest that the low levels of osterix expression remaining after knockdown are sufficient to block chondrogenesis, whereas higher expression may be required to promote osteoblastic differentiation.

A key role for autophagy and the autophagy gene Atg16l1 in mouse and human intestinal Paneth cells

Susceptibility to Crohn's disease, a complex inflammatory disease involving the small intestine, is controlled by over 30 loci. One Crohn's disease risk allele is in ATG16L1, a gene homologous to the essential yeast autophagy gene ATG16 (ref. 2). It is not known how ATG16L1 or autophagy contributes to intestinal biology or Crohn's disease pathogenesis. To address these questions, we generated and characterized mice that are hypomorphic for ATG16L1 protein expression, and validated conclusions on the basis of studies in these mice by analysing intestinal tissues that we collected from Crohn's disease patients carrying the Crohn's disease risk allele of ATG16L1. Here we show that ATG16L1 is a bona fide autophagy protein. Within the ileal epithelium, both ATG16L1 and a second essential autophagy protein ATG5 are selectively important for the biology of the Paneth cell, a specialized epithelial cell that functions in part by secretion of granule contents containing antimicrobial peptides and other proteins that alter the intestinal environment. ATG16L1- and ATG5-deficient Paneth cells exhibited notable abnormalities in the granule exocytosis pathway. In addition, transcriptional analysis revealed an unexpected gain of function specific to ATG16L1-deficient Paneth cells including increased expression of genes involved in peroxisome proliferator-activated receptor (PPAR) signalling and lipid metabolism, of acute phase reactants and of two adipocytokines, leptin and adiponectin, known to directly influence intestinal injury responses. Importantly, Crohn's disease patients homozygous for the ATG16L1 Crohn's disease risk allele displayed Paneth cell granule abnormalities similar to those observed in autophagy-protein-deficient mice and expressed increased levels of leptin protein. Thus, ATG16L1, and probably the process of autophagy, have a role within the intestinal epithelium of mice and Crohn's disease patients by selective effects on the cell biology and specialized regulatory properties of Paneth cells.

Intratracheal administration of third-generation lentivirus vector encoding MPT51 from Mycobacterium tuberculosis induces specific CD8+ T-cell responses in the lung

The present study evaluates the potential of improved third-generation lentivirus vector with respect to their use as an in vivo-administered T-cell vaccine against tuberculosis. Intratracheal administration of the lentivirus vector encoding MPT51 of Mycobacterium tuberculosis could induce MPT51-specific CD8+ T cells in the mediastinal lymph nodes 2 weeks after the administration. The vaccination could generate MPT51-specific memory CD8+ T cells in the lung, but not in the lymph nodes. Further, a single intratracheal immunization of MPT51 lentiviral vaccine decreased significantly the number of virulent M. tuberculosis in the lung after intratracheal challenge of the bacillus. These findings suggest that intratracheal immunization of the third-generation lentiviral vaccines is a promising vaccination strategy against pulmonary tuberculosis.

Berberine and its more biologically available derivative, dihydroberberine, inhibit mitochondrial respiratory complex I: a mechanism for the action of berberine to activate AMP-activated protein kinase and improve insulin action

OBJECTIVE

Berberine (BBR) activates AMP-activated protein kinase (AMPK) and improves insulin sensitivity in rodent models of insulin resistance. We investigated the mechanism of activation of AMPK by BBR and explored whether derivatization of BBR could improve its in vivo efficacy.

RESEARCH DESIGN AND METHODS

AMPK phosphorylation was examined in L6 myotubes and LKB1(-/-) cells, with or without the Ca(2+)/calmodulin-dependent protein kinase kinase (CAMKK) inhibitor STO-609. Oxygen consumption was measured in L6 myotubes and isolated muscle mitochondria. The effect of a BBR derivative, dihydroberberine (dhBBR), on adiposity and glucose metabolism was examined in rodents fed a high-fat diet. RESULTS; We have made the following novel observations: 1) BBR dose-dependently inhibited respiration in L6 myotubes and muscle mitochondria, through a specific effect on respiratory complex I, similar to that observed with metformin and rosiglitazone; 2) activation of AMPK by BBR did not rely on the activity of either LKB1 or CAMKKbeta, consistent with major regulation at the level of the AMPK phosphatase; and 3) a novel BBR derivative, dhBBR, was identified that displayed improved in vivo efficacy in terms of counteracting increased adiposity, tissue triglyceride accumulation, and insulin resistance in high-fat-fed rodents. This effect is likely due to enhanced oral bioavailability.

CONCLUSIONS

Complex I of the respiratory chain represents a major target for compounds that improve whole-body insulin sensitivity through increased AMPK activity. The identification of a novel derivative of BBR with improved in vivo efficacy highlights the potential importance of BBR as a novel therapy for the treatment of type 2 diabetes.

Lentiviral vector-mediated SERCA2 gene transfer protects against heart failure and left ventricular remodeling after myocardial infarction in rats

Reduced expression of the SERCA2 gene impairs the calcium-handling and contractile functions of the heart. We developed an SERCA2 gene transfer system using lentiviral vectors, and examined the long-term effect of SERCA2 gene transfer in the rat ischemic heart failure model. A lentiviral vector containing the SERCA2 gene was infused into a rat heart by hypothermic intracoronary delivery 2 weeks after myocardial infarction (MI). The transduction efficiency was approximately 40%. Six months after transduction, echocardiogram and pressure-volume measurements revealed that the SERCA2 gene transfer had significantly protected against left ventricular (LV) dilation, and had improved systolic and diastolic function, resulting in reduction in mortality rates. The brain natriuretic peptide mRNA level showed a significantly decrease and the phosphorylation level of serine residue of phospholamban (PLN) showed an increase in the Lenti-SERCA2-transduced heart. Further, DNA microarray analysis disclosed that SERCA2 gene transfer had increased cardioprotective gene expression and lowered the expression of genes that are known to exacerbate heart failure. The SERCA2 gene was successfully integrated into the host heart, induced favorable molecular remodeling, prevented LV geometrical remodeling, and improved the survival rate. These results suggest that a strategy to compensate for reduced SERCA2 gene expression by lentiviral vectors serves as a positive inotropic, lucitropic, and cardioprotective therapy for post-MI heart failure.

Differential contribution of NFATc2 and NFATc1 to TNF-alpha gene expression in T cells

The NFAT family transcription factors play crucial roles in immunological and other biological events; however, the functional differences among NFAT members have not been fully elucidated. This study investigated the relative contribution of NFATc2 and NFATc1 to the transactivation of cytokine genes in T cells. Ectopic expression of NFATc2 but not NFATc1, especially its short isoform, enhanced TNF-alpha synthesis in human T cells at the gene transcription level, whereas both NFATs augmented IL-2 expression. In addition, a reduction of the shortest NFATc1 isoform using RNA interference technology failed to suppress TNF-alpha expression. The promoter/enhancer activity of the NFAT-binding site in the TNF-alpha gene was up-regulated by NFATc2 but not by NFATc1, whereas both NFATs associated similarly with this region. A study of mRNA expression using NFATc2/NFATc1 chimeric molecules revealed that the enhancing activity of NFAT on the TNF-alpha gene was lost by truncation of its C-terminal transactivation domain. In addition, this domain derived from NFATc2 behaved as a dominant negative against the NFAT site in TNF-alpha promoter-dependent transcriptional activity in T cells. We conclude that the C-terminal transactivation domain in NFAT is crucial for TNF-alpha gene expression in human T cells.