Stanford University

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  • Harini Chakravarthy

    Harini Chakravarthy

    Postdoctoral Research Fellow, Developmental Biology

    Current Research and Scholarly Interests The discovery that insulin-producing ?-cells can be generated from cell sources within and outside the pancreas is of fundamental importance in terms of developing novel treatment strategies for diabetes. A major caveat to this is our relatively poor understanding of the players involved in this process and the lack of molecular characterization of the ?converted? ?-cells. This knowledge is key to our success in enhancing this process to its maximum therapeutic potential and efficiency. In this context, recent work has shown that ?-cells can be used as a source to generate ?-cells under conditions of near-total ?-cell depletion in mice. However the molecular mechanisms regulating ?-cell identity are unknown. This knowledge would allow us to harness the potential of ?-cells to give rise to ?-cells in diabetic patients where pancreatic ?-cells tend to be in abundant supply within the pancreas. My work in the laboratory has elucidated the role of two genes in maintaining ?-cell identity: Dnmt1 and Arx. Dnmt1, a DNA methyltransferase methylates DNA and is involved in gene repression. Arx is a transcription factor that is essential for ?-cell specification during embryogenesis. My work demonstrates that conditional in vivo inactivation of Dnmt1 and Arx in adult ?-cells causes them to convert into insulin producing ?-like-cells demonstrating the necessity of these two factors in maintaining ?-cell fate. Further functional characterization of these ?converted? cells will elucidate the extent to which ?-to- ?-cell conversion has occurred in these animals. I am also assessing the individual contributions of Dnmt1 and Arx in maintaining adult ?-cell identity.

  • Nicolas Denans

    Nicolas Denans

    Postdoctoral Research Fellow, Developmental Biology

    Current Research and Scholarly Interests I am interested in deciphering how cells communicate within intricate landscape and over long distance to establish precise gradients of signaling molecules that pattern many organs during vertebrate development. . For decades, most classical textbooks have conceptualized such signaling proteins as ?diffusible? molecules, known as morphogens, that transverse many cell diameters to pattern a field of cells. Recently, our lab, using a novel high resolution live imaging method, showed that, in the vertebrate limb, all cells extend very long and thin actin-based cellular protrusions termed specialized filopodia that connect cells over long distance. Moreover, they showed that a morphogen, Sonic Hedgehog, can travel along this meshwork of filopodia and hypothesize that morphogen transport through filopodia could account for the precise formation of morphogen gradients that pattern the limb bud. These filopodia are actin-based thus the main challenge is to be able to manipulate them without affecting the rest of the actin cytoskeleton. Currently, by combining live cell imaging, bioengineering and optogenetic I am trying to precisely manipulate these filopodia (modify size, orientation, formation) to directly assess their function in long-range cell communication and signaling gradient establishment.

  • Chloe Girard

    Chloe Girard

    Postdoctoral Research Fellow, Developmental Biology

    Bio I am a postdoc at Standord University (California, USA) working on meiosis and recombination in C.elegans in Anne Villeneuve's lab. I previously conducted a PhD thesis at INRA de Versailles (France) under the direction of RaphaŽl Mercier on new genes controlling meiotic recombination level in Arabidopsis. I am interested in genetics, epigenetics, evolution but also in popularization of science.

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