High prevalence of copy number variations in the Japanese participants with suspected MODY.

Maturity-Onset Diabetes of the Young (MODY) is a diabetes mellitus subtype caused by a single gene. The detection rate of the responsible gene is 27% in the United Kingdom, indicating that the causative gene remains unknown in the majority of clinically diagnosed MODY cases. To improve the detection rate, we applied comprehensive genetic testing using whole exome sequencing (WES) followed by Multiplex Ligation-dependent Probe Amplification (MLPA) and functional analyses. Twenty-one unrelated Japanese participants with MODY were enrolled in the study. To detect copy number variations (CNVs), WES was performed first, followed by MLPA analysis for participants who were negative on the basis of WES. Undetermined variants were analyzed according to their functional properties. WES identified 7 pathogenic and 3 novel likely pathogenic variants in the 21 participants. Functional analyses revealed that 1 in 3 variants was pathogenic. MLPA analysis applied to the remaining 13 undetermined samples identified 4 cases with pathogenic CNVs: 3 in HNF4A and 1 in HNF1B. Pathogenic variants were identified in 12 participants (12/21, 57.1%) - relatively high rate reported to date. Notably, one-third of the participants had CNVs in HNF4A or HNF1B, indicating a limitation of WES-only screening.

BCL7B, a SWI/SNF complex subunit, orchestrates cancer immunity and stemness.

Cancer is one of the main causes of human death. Here, we focus on the B-cell lymphoma 7 protein family member B (BCL7B) gene, an accessory subunit of the SWI/SNF chromatin-remodelling complex. To characterize the function of BCL7B, heterozygous BCL7B-deficient stomach cancer cell lines were generated with the CRISPR/Cas9 genome editing system. The comprehensive gene expression patterns were compared between parental cells and each ΔBCL7B cell line by RNA-seq. The results showed marked downregulation of immune-related genes and upregulation of stemness-related genes in the ΔBCL7B cell lines. Moreover, by ChIP-seq analysis with H3K27me3 antibody, the changes of epigenetic modification sequences were compared between parental cells and each ΔBCL7B cell line. After machine learning, we detected the centroid sequence changes, which exerted an impact on antigen presentation. The regulation of BCL7B expression in cancer cells gives rise to cancer stem cell-like characteristics and the acquisition of an immune evasion phenotype.

A novel pathogenic variant in the glucokinase gene found in two Japanese siblings with maturity-onset diabetes of the young 2.

Glucokinase is a glycolytic enzyme that catalyzes the phosphorylation of glucose to glucose-6-phospate in the first step of the glycolytic pathway. It also regulates the threshold for insulin secretion from pancreatic beta cells by catalyzing the phosphorylation of glucose and plays an important role as a glucose sensor. Pathogenic variants in the glucokinase gene (GCK) cause non-progressive but persistent mild fasting hyperglycemia, also recognized as maturity-onset diabetes of the young 2 (MODY2). This report presents the case of two Japanese siblings with MODY2, who were initially diagnosed with impaired glucose intolerance at 20 and 17 years of age, and later developed diabetes mellitus. They had no history of obesity, were negative for islet-related autoantibodies and their serum C-peptide level were within the normal range. Diabetic complications were not observed. Next-generation sequencing revealed a novel heterozygous variant in GCK (NM_000162.5: c.1088A>G, p.Asp363Gly) in both siblings. This variant has not been reported previously. In silico functional analyses, using SIFT and MutationTaster, suggested that the variant was damaging. To confirm the functional impact of the mutated GCK, the HiBiT-tagged p.Asp363Gly variant and the wild-type GCK were transiently expressed in HEK293T cells. The cells expressing the variant GCK exhibited 79% less bioluminescence, compared to those expressing the wild-type GCK, suggesting that the pathophysiology of the variant was a result of haploinsufficiency.

Inhibition of the integrin signal constitutes a mouse iPS cell niche.

Stem cells are regulated by their surrounding microenvironments, called niche, such as cell-cell interaction and extracellular matrix. Classically, feeder cells as a niche have been used in the culture of iPS cells from both the mouse and the human. However, the regulation mechanism of stem cells by feeder cells as a niche still have been partially unclear. In this study, we used three murine iPS cell lines, iPS-MEF-Ng-20D-17, iPS-MEF-Ng-178B-5 and iPS-MEF-Fb/Ng-440A-3, which were generated by different reprogramming methods. In general, these cell lines commonly need the feeder cells as a niche to culture. Recently, the effect of substrate stiffness is known in stem cell study. First, we focused on the mechanical properties of feeder cells, and then we speculated that feeder-less culture might be made possible by using molecules in place of the mechanical properties of the niche. Finally, we found that the combination of disintegrin (echistatin) and 2i (GSK3 inhibitor and MEK inhibitor) is a sufficient condition for three murine iPS culture. This novel method of mimicking the murine iPS cell niche may be useful to understand signaling pathways to maintain the pluripotency of stem cells.

Chromatin plasticity as a differentiation index during muscle differentiation of C2C12 myoblasts.

Skeletal muscle undergoes complicated differentiation steps that include cell-cycle arrest, cell fusion, and maturation, which are controlled through sequential expression of transcription factors. During muscle differentiation, remodeling of the epigenetic landscape is also known to take place on a large scale, determining cell fate. In an attempt to determine the extent of epigenetic remodeling during muscle differentiation, we characterized the plasticity of the chromatin structure using C2C12 myoblasts. Differentiation of C2C12 cells was induced by lowering the serum concentration after they had reached full confluence, resulting in the formation of multi-nucleated myotubes. Upon induction of differentiation, the nucleus size decreased whereas the aspect ratio increased, indicating the presence of force on the nucleus during differentiation. Movement of the nucleus was also suppressed when differentiation was induced, indicating that the plasticity of chromatin changed upon differentiation. To evaluate the histone dynamics during differentiation, FRAP experiment was performed, which showed an increase in the immobile fraction of histone proteins when differentiation was induced. To further evaluate the change in the histone dynamics during differentiation, FCS was performed, which showed a decrease in histone mobility on differentiation. We here show that the plasticity of chromatin decreases upon differentiation, which takes place in a stepwise manner, and that it can be used as an index for the differentiation stage during myogenesis using the state diagram developed with the parameters obtained in this study.

Delta-opioid receptor activation promotes mesenchymal stem cell survival via PKC/STAT3 signaling pathway.

BACKGROUND: The survival of stem cells upon transplantation into ischemic myocardium is a major concern in cell-based therapy. In this study, we tested the hypothesis that activation of opioid receptors would enhance the survival of mesenchymal stem cells (MSCs) upon exposure to an injury stimulus. METHODS AND RESULTS: MSCs were obtained from rat bone marrow and cultured in basal DMEM cell culture medium. Delta-opioid receptor (DOR) was present in MSCs as examined by reverse transcription-polymerase chain reaction and immunochemistry. Activation of DOR with 5µmol/L SNC80 (DOR agonist) for 24h significantly enhanced MSC viability upon exposure to 5µg/ml actinomycin D as determined by TUNEL and MTT assays. The cytoprotection was abolished with 20µmol/L naltrindole hydrochloride (a DOR antagonist). Treatment of the cells with 1.5µmol/L chelerythrine (protein kinase C inhibitor) and 1.25µmol/L WP1066 (signal transducer and activator of transcription 3 (STAT3) inhibitor) blocked SNC80-induced cytoprotection. Furthermore, treatment of the cells with chelerythrine also blocked STAT3-phosphorylation and Mcl-1 gene expression. CONCLUSIONS: Taken together, the results indicate that DOR plays a critical role in MSC survival upon exposure to actinomycin D through activation of protein kinase C and its downstream signaling molecules STAT3 and Mcl-1. DOR may be a novel therapeutic target for stem cell survival during cell-based therapy.

Thin filament-reconstituted skinned muscle fibers for the study of muscle physiology.

We review the use of thin filament-reconstituted muscle fibers in the study of muscle physiology. Thin filament extraction and reconstitution protocol is a powerful technique to study the role of each component of the thin filament. It is also useful for studying the properties of genetically modified molecules such as actin and tropomyosin. We also review the combination of this protocol with sinusoidal analysis, which will provide a solid technique for determining the effect of regulatory proteins on actomyosin interaction and concomitant cross-bridge kinetics. We suggest that thin filament-reconstituted muscle fibers are an ideal system for studying muscle physiology especially when gene modifications of actin or tropomyosin are involved.

Cross-talk between the pathways leading to the induction of apoptosis and the secretion of tumor necrosis factor-alpha in ricin-treated RAW 264.7 cells.

Ricin induced apoptotic nuclear morphological changes in mouse macrophage cell line RAW264.7 cells at concentrations sufficient to cause severe protein synthesis inhibition. Ricin also induced the release of tumor necrosis factor-alpha (TNF-alpha) from this cell line in a dose-dependent manner but the profile was bell-shaped. However, the isolated galactose-specific ricin B-chain had no such effects. These results suggest that the receptor-binding of ricin through the B-chain is not enough, and subsequent attack on the intracellular target, i.e., the 28S ribosomal RNA (rRNA), by the A-chain of internalized ricin is required for the effects of ricin. Z-D-CH2-DCB, a caspase family inhibitor, showed potent inhibition of the release of TNF-alpha from RAW264.7 cells as well as blockage of the induction of apoptosis by ricin. Furthermore, SB202190, a specific P38 mitogen-activated protein (MAP) kinase inhibitor that strongly inhibits the release of TNF-alpha, also showed significant inhibition of ricin-induced apoptosis. These results suggest that there may be cross-talk between the pathways leading to the release of TNF-alpha and apoptosis. Time course analysis revealed that the activation of p38 MAP kinase started prior to the induction of TNF-alpha release and apoptosis. Since the activation of p38 MAP kinase in ricin-treated RAW264.7 cells was not prevented by Z-D-CH2-DCB, the activation of p38 MAP kinase may occur upstream of the caspase cascade. Among the other protein synthesis inhibitors examined, modeccin and anisomycin, which can trigger a ribotoxic stress response similar to ricin, induced the release of TNF-alpha, but emetine and cycloheximide did not. These results suggest that the specific attack on the 28S ribosomal RNA and the resulting ribotoxic stress response may trigger the multiple signal transduction pathways through the activation of p38 MAP kinase, which in turn leads to TNF-alpha release and apoptosis.

Culturing of mouse and human cells on soft substrates promote the expression of stem cell markers.

Substrate elasticity is a potent regulator of the cell state. Soft substrates have been shown to promote the homogeneous self-renewal of mouse embryonic stem cells through the down-regulation of cell-matrix tractions. We therefore investigated whether soft substrates promote the reprogramming of somatic cells into induced pluripotent stem (iPS) cells. After retroviral infection with five factors, Oct3/4, Klf4, Sox2, Lin28 and Nanog, mouse embryonic fibroblasts (MEFs) were cultured on several artificial substrates of varying elasticity and examined for the expression of pluripotency genes. When MEFs were cultured on soft (<0.1 kPa) polyacrylamide gels coated with gelatin, the expressions of Nanog and Oct3/4 genes were higher than in cells cultured on rigid plastic dishes (∼10(6) kPa). The same result was obtained at higher elasticity (0.5 kPa) for adult human dermal fibroblasts (HDFa). We also examined whether reprogramming could be enhanced on soft substrates without exogenous gene introduction, finding that cells cultured on soft substrates in the presence of chemicals known to promote cell reprogramming exhibited up-regulated stem cell markers. These results suggest that controlling the substrate stiffness can enhance the initiation of cell reprogramming, which may lead to effective and reproducible iPS cell production.

Heart extracellular matrix supports cardiomyocyte differentiation of mouse embryonic stem cells.

We have evaluated the effect of heart extracellular matrix (ECM) on the cardiomyocyte differentiation of mouse embryonic stem cells (ES cells) using de-cellularized heart tissue. Several lines of evidence indicate that ECM plays significant roles in cell proliferation, cell death and differentiation, but role of ECM possessing a 3D structure in differentiation has not been studied in detail. We found that there are substantial differences in the quantitative protein profiles of ECM in SDS-treated heart tissue compared to that of liver tissue, as assessed by iTRAQ™ quantitative proteomics analysis. When mouse ES cells were cultured on thin (60 µm) sections of de-cellularized tissue, the expression of cardiac myosin heavy chain (cMHC) and cardiac troponin I (cTnI) was high in ES cells cultured on heart ECM compared with those cultured on liver ECM. In addition, the protein expression of cMHC and cTnI was detected in cells on heart ECM after 2 weeks, which was not detectable in cells on liver ECM. These results indicate that heart ECM plays a critical role in the cardiomyocyte differentiation of ES cells. We propose that tissue-specific ECM induced cell lineage specification through mechano-transduction mediated by the structure, elasticity and components of ECM.

Expression and functional analysis of musashi-like genes in planarian CNS regeneration.

The remarkable regenerative ability of planarians is made possible by a system of pluripotent stem cells. Recent molecular biological and ultrastructural studies have revealed that planarian stem cells consist of heterogeneous populations, which can be classified into several subsets according to their differential expression of RNA binding protein genes. In this study, we focused on planarian musashi family genes. Musashi encodes an evolutionarily conserved RNA binding protein known to be expressed in neural lineage cells, including neural stem cells, in many animals. Here, we investigated whether planarian musashi-like genes can be used as markers for detecting neural fate-restricted cells. Three musashi family genes, DjmlgA, DjmlgB and DjmlgC (Dugesia japonica musashi-like gene A, B, C), and Djdmlg (Dugesia japonica DAZAP-like/musashi-like gene) were obtained by searching a planarian EST database and 5' RACE, and each was found to have two RNA recognition motifs. We analyzed the types of cells expressing DjmlgA, DjmlgB, DjmlgC and Djdmlg by in situ hybridization, RT-PCR and single-cell RT-PCR analysis. Although Djdmlg was expressed in X-ray-sensitive stem cells and various types of differentiated cells, expression of the other three musashi-like genes was restricted to neural cells, as we expected. Further detailed analyses yielded the unexpected finding that these three planarian musashi family genes were predominantly expressed in X-ray-resistant differentiated neurons, but not in X-ray-sensitive stem cells. RNAi experiments suggested that these planarian musashi family genes might be involved in neural cell differentiation after neural cell-fate commitment.

Characterization and categorization of fluorescence activated cell sorted planarian stem cells by ultrastructural analysis.

Planarians have regenerative ability made possible by pluripotent stem cells referred to as neoblasts. Classical ultrastructural studies have indicated that stem cells can be distinguished by a unique cytoplasmic structure known as the chromatoid body and their undifferentiated features, and they are specifically eliminated by X-ray irradiation. Recently, by using fluorescence activated cell sorting (FACS), planarian cells were separated into two X-ray-sensitive fractions (X1 and X2) and an X-ray-insensitive fraction (XIS) according to DNA content and cytoplasmic size. Here we analyzed the fractionated cells by transmission electron microscopy (TEM). First, we found that both undifferentiated cells (stem cells) and regenerative cells (differentiating cells) were concentrated in the X1 fraction containing the S/G2/M phase cells. The regenerative cells were considered to be committed stem cells or progenitor cells, suggesting that some stem cells may maintain proliferative ability even after cell fate-commitment. Second, we succeeded in identifying a new type of stem cells, which were small in size with few chromatoid bodies and a heterochromatin-rich nucleus. Interestingly, they were concentrated in the X2 fraction, containing G0/G1 phase cells. These results suggest that planarian stem cells are not homogeneous, but may consist of heterogeneous populations, like mammalian stem cells.

Isolation of planarian X-ray-sensitive stem cells by fluorescence-activated cell sorting.

The remarkable capability of planarian regeneration is mediated by a group of adult stem cells referred to as neoblasts. Although these cells possess many unique cytological characteristics (e.g. they are X-ray sensitive and contain chromatoid bodies), it has been difficult to isolate them after cell dissociation. This is one of the major reasons why planarian regenerative mechanisms have remained elusive for a long time. Here, we describe a new method to isolate the planarian adult stem cells as X-ray-sensitive cell populations by fluorescence-activated cell sorting (FACS). Dissociated cells from whole planarians were labeled with fluorescent dyes prior to fractionation by FACS. We compared the FACS profiles from X-ray-irradiated and non-irradiated planarians, and thereby found two cell fractions which contained X-ray-sensitive cells. These fractions, designated X1 and X2, were subjected to electron microscopic morphological analysis. We concluded that X-ray-sensitive cells in both fractions possessed typical stem cell morphology: an ovoid shape with a large nucleus and scant cytoplasm, and chromatoid bodies in the cytoplasm. This method of isolating X-ray-sensitive cells using FACS may provide a key tool for advancing our understanding of the stem cell system in planarians.