Planarian fibroblast growth factor receptor homologs expressed in stem cells and cephalic ganglions

Authors

  • Kazuya Ogawa,

    1. Laboratory of Regeneration Biology, Department of Life Science, Faculty of Science, Himeji Institute of Technology, Harima Science Garden City, Akou, Hyogo 678-1297,
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  • Chiyoko Kobayashi,

    1. Evolutionary Regeneration Biology Group, RIKEN Center for Developmental Biology, Kobe, Hyogo 650-0047 and
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  • Tetsutaro Hayashi,

    1. Evolutionary Regeneration Biology Group, RIKEN Center for Developmental Biology, Kobe, Hyogo 650-0047 and
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  • Hidefumi Orii,

    1. Laboratory of Regeneration Biology, Department of Life Science, Faculty of Science, Himeji Institute of Technology, Harima Science Garden City, Akou, Hyogo 678-1297,
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  • Kenji Watanabe,

    1. Laboratory of Regeneration Biology, Department of Life Science, Faculty of Science, Himeji Institute of Technology, Harima Science Garden City, Akou, Hyogo 678-1297,
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  • Kiyokazu Agata

    Corresponding author
    1. Evolutionary Regeneration Biology Group, RIKEN Center for Developmental Biology, Kobe, Hyogo 650-0047 and
    2. Laboratory of Regeneration and Developmental Biology, Department of Biology, Faculty of Science, University of Okayama, 3-1-1 Tsushima-naka, Okayama, 700-8530, Japan
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* Author to whom all correspondence should be addressed. Email: agata@cdb.riken.go.jp

Abstract

The strong regenerative capacity of planarians is considered to reside in the totipotent somatic stem cell called the ‘neoblast’. However, the signal systems regulating the differentiation/growth/migration of stem cells remain unclear. The fibroblast growth factor (FGF)/FGF receptor (FGFR) system is thought to mediate various developmental events in both vertebrates and invertebrates. We examined the molecular structures and expression of DjFGFR1 and DjFGFR2, two planarian genes closely related to other animal FGFR genes. DjFGFR1 and DjFGFR2 proteins contain three and two immunoglobulin-like domains, respectively, in the extracellular region and a split tyrosine kinase domain in the intracellular region. Expression of DjFGFR1 and DjFGFR2 was observed in the cephalic ganglion and mesenchymal space in intact planarians. In regenerating planarians, accumulation of DjFGFR1-expressing cells was observed in the blastema and in fragments regenerating either a pharynx or a brain. In X-ray-irradiated planarians, which had lost regenerative capacity, the number of DjFGFR1-expressing cells in the mesenchymal space decreased markedly. These results suggest that the DjFGFR1 protein may be involved in the signal systems controlling such aspects of planarian regeneration as differentiation/growth/migration of stem cells.

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