The Experts below are selected from a list of 17568 Experts worldwide ranked by ideXlab platform

Srinath C Sampath - One of the best experts on this subject based on the ideXlab platform.

  • induction of muscle stem cell quiescence by the secreted Niche Factor oncostatin m
    Nature Communications, 2018
    Co-Authors: Andrew T. V. Ho, Stephane Y Corbel, Srinath C Sampath, Joshua D Millstone
    Abstract:

    The balance between stem cell quiescence and proliferation in skeletal muscle is tightly controlled, but perturbed in a variety of disease states. Despite progress in identifying activators of stem cell proliferation, the Niche Factor(s) responsible for quiescence induction remain unclear. Here we report an in vivo imaging-based screen which identifies Oncostatin M (OSM), a member of the interleukin-6 family of cytokines, as a potent inducer of muscle stem cell (MuSC, satellite cell) quiescence. OSM is produced by muscle fibers, induces reversible MuSC cell cycle exit, and maintains stem cell regenerative capacity as judged by serial transplantation. Conditional OSM receptor deletion in satellite cells leads to stem cell depletion and impaired regeneration following injury. These results identify Oncostatin M as a secreted Niche Factor responsible for quiescence induction, and for the first time establish a direct connection between induction of quiescence, stemness, and transplantation potential in solid organ stem cells.

Roel Nusse - One of the best experts on this subject based on the ideXlab platform.

  • Wnt signaling and stem cell control
    Cell Research, 2008
    Co-Authors: Roel Nusse
    Abstract:

    Wnt signaling has been implicated in the control over various types of stem cells and may act as a Niche Factor to maintain stem cells in a self-renewing state. As currently understood, Wnt proteins bind to receptors of the Frizzled and LRP families on the cell surface. Through several cytoplasmic relay components, the signal is transduced to ß-catenin, which then enters the nucleus and forms a complex with TCF to activate transcription of Wnt target genes. Wnts can also signal through tyrosine kinase receptors, in particular the ROR and RYK receptors, leading to alternative modes of Wnt signaling. During the growth of tissues, these ligands and receptors are dynamically expressed, often transcriptionally controlled by Wnt signals themselves, to ensure the right balance between proliferation and differentiation. Isolated Wnt proteins are active on a variety of stem cells, including neural, mammary and embryonic stem cells. In general, Wnt proteins act to maintain the undifferentiated state of stem cells, while other growth Factors instruct the cells to proliferate. These other Factors include FGF and EGF, signaling through tyrosine kinase pathways.

Yumiko Saga - One of the best experts on this subject based on the ideXlab platform.

  • FGF8-FGFR1 Signaling Acts as a Niche Factor for Maintaining Undifferentiated Spermatogonia in the Mouse
    Biology of reproduction, 2014
    Co-Authors: Kazuteru Hasegawa, Yumiko Saga
    Abstract:

    ABSTRACT In mammalian testes, spermatogonial stem cells (SSCs) maintain spermatogenesis over a long period of time by undergoing self-renewal and differentiation. SSCs are among the most primitive of spermatogenic cells (undifferentiated spermatogonia), and their activities are strictly regulated by extrinsic Niche Factors. However, the Factors that constitute a testicular Niche remain poorly understood. In this study, we demonstrate that fibroblast growth Factor (FGF) signaling maintains undifferentiated spermatogonia through activating ERK1/2 signaling in vivo. Undifferentiated spermatogonia comprise GFRA1+ and NANOS3+ subpopulations, which are likely to undergo self-renewal and enter the differentiation pathway, respectively. In the testis, Fgfr1 was expressed in the entire population of undifferentiated spermatogonia, and deleting FGFR1 in spermatogenic cells partially inactivated ERK1/2 and resulted in reduced numbers of both GFRA1+ and NANOS3+ cells. In addition, Fgf8 was expressed in spermatogenic ...

  • MEK/ERK signaling directly and indirectly contributes to the cyclical self-renewal of spermatogonial stem cells.
    Stem cells (Dayton Ohio), 2013
    Co-Authors: Kazuteru Hasegawa, Satoshi H. Namekawa, Yumiko Saga
    Abstract:

    Coordination of stem cell fate is regulated by extrinsic Niche signals and stem cell intrinsic Factors. In mammalian testes, spermatogonial stem cells maintain constant production of abundant spermatozoa by alternating between self-renewal and differentiation at regular intervals according to a periodical program known as the seminiferous epithelial cycle. Although retinoic acid (RA) signaling has been suggested to direct the cyclical differentiation of spermatogonial stem cells, it remains largely unclear how their cycle-dependent self-renewal/proliferation is regulated. Here, we show that MEK/ERK signaling contributes to the cyclical activity of spermatogonial stem cells. We found that ERK1/2 is periodically activated in Sertoli cells during the stem cell self-renewal/proliferation phase, and that MEK/ERK signaling is required for the stage-related expression of the critical Niche Factor GDNF. In addition, ERK1/2 is activated in GFRα1-positive spermatogonial stem cells under the control of GDNF and prevent them from being differentiated. These results suggest that MEK/ERK signaling directly and indirectly maintains spermatogonial stem cells by mediating a signal that promotes their periodical self-renewal/proliferation. Conversely, RA signaling directly and indirectly induces differentiation of spermatogonial stem cells. We propose that temporally regulated activations of RA signaling and a signal regulating MEK/ERK antagonistically coordinates the cycle-related activity of spermatogonial stem cells.

Aitor Arrizabalagaescudero - One of the best experts on this subject based on the ideXlab platform.

  • assessing Niche partitioning of co occurring sibling bat species by dna metabarcoding
    Molecular Ecology, 2018
    Co-Authors: Aitor Arrizabalagaescudero, Elizabeth L Clare, Egoitz Salsamendi, Antton Alberdi, Inazio Garin, Joxerra Aihartza, Urtzi Goiti
    Abstract:

    Niche partitioning through foraging is a mechanism likely involved in facilitating the coexistence of ecologically similar and co-occurring animal species by separating their use of resources. Yet, this mechanism is not well understood in flying insectivorous animals. This is particularly true of bats, where many ecologically similar or cryptic species coexist. The detailed analysis of the foraging Niche in sympatric, cryptic sibling species provides an excellent framework to disentangle the role of specific Niche Factors likely involved in facilitating coexistence. We used DNA metabarcoding to determine the prey species consumed by a population of sympatric sibling Rhinolophus euryale and Rhinolophus mehelyi whose use of habitat in both sympatric and allopatric ranges has been well established through radio tracking. Although some subtle dietary differences exist in prey species composition, the diet of both bats greatly overlapped (Ojk  = 0.83) due to the consumption of the same common and widespread moths. Those dietary differences we did detect might be related to divergences in prey availabilities among foraging habitats, which prior radio tracking on the same population showed are differentially used and selected when both species co-occur. This minor dietary segregation in sympatry may be the result of foraging on the same prey-types and could contribute to reduce potential competitive interactions (e.g., for prey, acoustic space). Our results highlight the need to evaluate the spatial Niche dimension in mediating the co-occurrence of similar insectivorous bat species, a Niche Factor likely involved in processes of bat species coexistence.

A. Gannier - One of the best experts on this subject based on the ideXlab platform.

  • Ecological Niches of three teuthophageous odontocetes in the northwestern Mediterranean Sea
    Ocean Science, 2008
    Co-Authors: Emilie Praca, A. Gannier
    Abstract:

    In the northwestern Mediterranean Sea, sperm whales, pilot whales and Risso's dolphins prey exclusively or preferentially on cephalopods. In order to evaluate their competition, we modelled their habitat suitability with the Ecological Niche Factor Analysis (ENFA) and compared their ecological Niches using a discriminant analysis. We used a long term (1995–2005) small boat data set, with visual and acoustic (sperm whale) detections. Risso's dolphin had the shallowest and the more spatially restricted principal habitat, mainly located on the upper part of the continental slope (640 m mean depth). With a wider principal habitat, at 1750 m depth in average, the sperm whale used a deeper part of the slope as well as the closest offshore waters. Finally, the pilot whale has the most oceanic habitat (2500 m mean depth) mainly located in the central Ligurian Sea and Provençal basin. Therefore, potential competition for food between these species may be reduced by the differentiation of their habitats.

  • Ecological Niche of three teuthophageous odontocetes in the northwestern Mediterranean Sea
    Ocean Science Discussions, 2007
    Co-Authors: Emilie Praca, A. Gannier
    Abstract:

    Abstract. In the northwestern Mediterranean Sea, sperm whales, pilot whales and Risso's dolphins prey on cephalopods exclusively or preferentially. In order to evaluate their competition, we modelled their habitat suitability with the Ecological Niche Factor Analysis (ENFA) and compared their ecological Niche using a discriminant analysis. We used a long term (1995–2005) small boat data set, with visual and acoustic (sperm whale) detections. Risso's dolphin had the shallowest and the more spatially restricted principal habitat, mainly located on the upper part of the continental slope (640 m mean depth). With a wider principal habitat, at 1750 m depth in average, the sperm whale used a deeper part of the slope as well as close offshore waters. Finally, the pilot whale has the most oceanic habitat (2500 m mean depth) mainly located in the central Ligurian Sea and Provençal basin. Therefore, potential competition for food between these species may be reduced by the differentiation of their ecological Niches.