Inceptor counteracts insulin signalling in ß-cells to control glycaemia.

Resistance to insulin and insulin-like growth factor 1 (IGF1) in pancreatic ß-cells causes overt diabetes in mice; thus, therapies that sensitize ß-cells to insulin may protect patients with diabetes against ß-cell failure1-3. Here we identify an inhibitor of insulin receptor (INSR) and IGF1 receptor (IGF1R) signalling in mouse ß-cells, which we name the insulin inhibitory receptor (inceptor; encoded by the gene Iir). Inceptor contains an extracellular cysteine-rich domain with similarities to INSR and IGF1R4, and a mannose 6-phosphate receptor domain that is also found in the IGF2 receptor (IGF2R)5. Knockout mice that lack inceptor (Iir-/-) exhibit signs of hyperinsulinaemia and hypoglycaemia, and die within a few hours of birth. Molecular and cellular analyses of embryonic and postnatal pancreases from Iir-/- mice showed an increase in the activation of INSR-IGF1R in Iir-/- pancreatic tissue, resulting in an increase in the proliferation and mass of ß-cells. Similarly, inducible ß-cell-specific Iir-/- knockout in adult mice and in ex vivo islets led to an increase in the activation of INSR-IGF1R and increased proliferation of ß-cells, resulting in improved glucose tolerance in vivo. Mechanistically, inceptor interacts with INSR-IGF1R to facilitate clathrin-mediated endocytosis for receptor desensitization. Blocking this physical interaction using monoclonal antibodies against the extracellular domain of inceptor resulted in the retention of inceptor and INSR at the plasma membrane to sustain the activation of INSR-IGF1R in ß-cells. Together, our findings show that inceptor shields insulin-producing ß-cells from constitutive pathway activation, and identify inceptor as a potential molecular target for INSR-IGF1R sensitization and diabetes therapy.

Enhancement of Cardiomyogenesis in Murine Stem Cells by Low-Intensity Ultrasound.

OBJECTIVES: Low-intensity ultrasound (LIUS) has been shown to enhance bone and cartilage regeneration from stem cells. The ease of its incorporation makes it an attractive mechanical stimulus for not only osteogenesis and chondrogenesis, but also cardiomyogenesis. However, to date, no study has investigated its effects on cardiomyogenesis from embryonic stem cells. METHODS: In this study, murine embryonic stem cells were differentiated via embryoid body formation and plating, and after 3 days they were subjected to daily 10 minutes of LIUS treatment with various conditions: (1) low-pulsed (21 mW/cm2 , 20% duty cycle), (2) low-continuous, (3) high-pulsed (147 mW/cm2 , 20% duty cycle), and (4) high-continuous LIUS. RESULTS: Low-pulsed and high-continuous LIUS had improved beating rates of contractile areas as well as increased late cardiac gene expressions, such as α- and ß-myosin heavy chain and cardiac troponin T, showing its benefits on cardiomyocyte differentiation. Meanwhile, an early endodermal marker, α-fetoprotein, was significantly attenuated after LIUS treatments. CONCLUSIONS: With these observations, it is demonstrated that LIUS simulation could enhance cardiomyogenesis from embryonic stem cells and increase its selectivity toward cardiomyocytes by reducing spontaneous differentiation.

Induced pluripotent stem cells: a new approach for physiological research.

The generation of induced pluripotent stem (iPS) cells by controlled delivery of reprogramming factors enables the derivation of pluripotent cells from a variety of somatic cell types. Patient-tailored iPS cells remove the major roadblock of immune rejection for clinical applications associated with the use of human embryonic stem (hES) cells. Beside therapeutic issues, iPS cell technology opens the door for broader research on human pluripotent cells because ethical limitations are lifted with iPS cells compared to hES cells. Scientists are now able to generate iPS cells for disease modelling and use them in basic research of physiological and pathophysiological models. In this concise review, we discuss the state of the art in the field of iPS cell induction by cell fusion or defined factors. Techniques to derive pluripotent cells from somatic sources are introduced and discussed, as well as some biological factors that influence the generation of iPS cells. We compare ES and iPS cells to answer the question whether these cells are identical, and we finish with an outlook on clinical research with iPS cells with a focus on cardiovascular medicine.

Publisher Correction: Utf1 contributes to intergenerational epigenetic inheritance of pluripotency.

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Utf1 contributes to intergenerational epigenetic inheritance of pluripotency.

Undifferentiated embryonic cell transcription factor 1 (Utf1) is expressed in pluripotent embryonic stem cells (ESCs) and primordial germ cells (PGCs). Utf1 expression is directly controlled by pluripotency factors Oct4 and Sox2, which form a ternary complex with the Utf1 enhancer. The Utf1 protein plays a role in chromatin organization and epigenetic control of bivalent gene expression in ESCs in vitro, where it promotes effective cell differentiation during exit from pluripotency. The function of Utf1 in PGCs in vivo, however, is not known. Here, we report that proper development of Utf1 null embryos almost entirely depends on the presence of functional Utf1 alleles in the parental germline. This indicates that Utf1's proposed epigenetic role in ESC pluripotency in vitro may be linked to intergenerational epigenetic inheritance in vivo. One component - or at least facilitator - of the relevant epigenetic mark appears to be Utf1 itself, since Utf1-driven tomato reporter and Utf1 are detected in mature germ cells. We also provide initial evidence for a reduced adult testis size in Utf1 null mice. Our findings thus point at unexpected functional links between the core ESC pluripotency factor network and epigenetic inheritance of pluripotency.

Use of UTF1 genetic control elements as iPSC reporter.

The reprogramming of adult somatic cells into an embryonic stem cell (ESC) state by various means has opened a new chapter in basic and applied life science. While this technology will create great opportunities for regenerative medicine, the more immediate impact is likely to be found in human disease modeling and drug testing/development. An important aspect in the latter contexts is the ability to reliably monitor the pluripotent stem cell state, in particular with respect to human cell reprogramming using patient-specific somatic cells and high-throughput screens. Undifferentiated transcription factor 1 (UTF1) belongs to the core transcriptional network characterizing pluripotency. UTF1 is involved in ESC-specific chromatin organization, and its expression pattern during cell reprogramming and subsequent differentiation appears to be tightly connected with the pluripotent stem cell state. Here, we capitalized on these features and generated a reliable reporter system that was used to monitor induced pluripotent stem cell (iPSC) formation and subsequent differentiation. Our reporter cassette comprises less than 2.3 kb and remains functional during many cell passages after genomic integration. The fact that the human UTF1 genetic control elements work in a mouse background and the demonstrated functionality of the reporter in an epigenetic state further qualifies this system as a versatile new tool for iPSC research.

Probing into the biological processes influenced by ESC factor and oncoprotein HMGA2 using iPSCs.

Induced pluripotent stem cells (iPSCs) are rapidly evolving into an important research tool due to their close resemblance with pluripotent embryonic stem cells (ESCs). Of particular interest at this point are iPSC applications in disease modeling and drug discovery/testing. The high mobility group AT-hook 2 (HMGA2) protein is a nonhistone chromatin factor normally expressed in ESCs and during early developmental stages. Aberrant HMGA2 expression is associated, for example, with abnormal body stature, diabetes mellitus, heart development and uterine leiomyomas. Furthermore, the protein is re-expressed in many primary tumor cells and plays an important role in metastasis. Here we used iPSC formation in conjunction with exogenous human HMGA2 expression to gain insight into biological functions of HMGA2. Gene expression profiling and gene ontology analyses showed that anatomical development and cell adhesion/differentiation processes are strongly affected by HMGA2. This could help to uncover, at the molecular level, some of the known phenotypic consequences of aberrant HMGA2 expression. Furthermore, our data showed that expression of key diabetes susceptibility genes is influenced by HMGA2, which revealed an interesting link to the recently indentified Lin28/let-7 pathway regulating mammalian glucose metabolism. Contrary to a previous report, our results indicate that HMGA2 is not involved in the regulation of telomerase gene expression. Finally, our data support a model in which tight regulation of intracellular HMGA2 levels is important both to maintain a pluripotent ESC state and to induce differentiation into certain cell lineages during later developmental stages.