title: Shisa2 promotes the maturation of somitic precursors and transition to the segmental fate in Xenopus embryos.
abstract: In vertebrate somitogenesis, FGF and Wnt signals constitute a morphogenetic gradient that controls the maturation of the presomitic mesoderm (PSM) as well as the transition to segmental units. It remains unclear, however, whether there is a regulatory mechanism that promotes the transition by a direct regulation of FGF and Wnt signaling in the PSM. Here we show that Shisa2, a member of a novel Shisa gene family, plays an essential role in segmental patterning during Xenopus somitogenesis. Shisa2 encodes an endoplasmic reticulum (ER) protein that cell-autonomously inhibits FGF and Wnt signaling by preventing the maturation and the cell-surface expression of their receptors. Shisa2 is expressed in the PSM and its knockdown caused a reduction in somite number by the delayed maturation of PSM and anterior shift of the transition; however, the phase of the segmental clock remained intact. These phenotypes were abolished by the inhibition of both FGF and Wnt signals, but by neither alone. We therefore propose that the individual inhibition of both types of signaling by the regulation of receptor maturation in the ER plays an essential role in the establishment of proper segmental patterning.
authors.affiliation: Laboratory for Vertebrate Body Plan, RIKEN Center for Developmental Biology, 2-2-3 Minatojima Minami, Chuo-ku, Kobe 650-0047, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nagano
authors.forename: Shoko
authors.initials: S
authors.lastname: Takehara
authors.forename: Maiko
authors.initials: M
authors.lastname: Takahashi
authors.forename: Shinichi
authors.initials: S
authors.lastname: Aizawa
authors.forename: Akihito
authors.initials: A
authors.lastname: Yamamoto
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019521:Body Patterning; D002454:Cell Differentiation; D017931:DNA Primers / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005346:Fibroblast Growth Factors / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D019170:Somites / Q000166:cytology / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism; D014981:Xenopus / Q000196:embryology* / Q000235:genetics* / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D017931:DNA Primers; D008565:Membrane Proteins; D051153:Wnt Proteins; D029867:Xenopus Proteins; D005346:Fibroblast Growth Factors