title: Homeogenetic inductive mechanism of segmentation in polychaete tail regeneration.
abstract: Segmentation is a body-patterning strategy in which new segments are specified from a segment-addition zone containing uncommitted cells. However, the cell-recruitment process is poorly understood. Here we investigated in detail the segmentation in a polychaete annelid, Perinereis nuntia (Lophotrochozoa), in which new segments emerge at the boundary between the posterior end of the segmented region and the terminal pygidium. Cells at this border synchronously remodel their chromatin, enter the cell cycle, and undergo oriented cell division, before being added to new segments. wingless is expressed at the posterior edge of the pre-existing segment, abutted by hedgehog in the first row of the new segment. Overstimulation of Wingless signaling caused excess cells to enter the cell cycle, prolonging segmentation and widening the new segment. Thus, segment addition may occur by a homeogenetic mechanism, in which Wingless expressed in the differentiated segment coordinates the stepwise recruitment of undifferentiated cells from the segment/pygidium boundary.
authors.affiliation: Laboratory for Morphogenetic Signaling, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.
authors.forename: Nao
authors.initials: N
authors.lastname: Niwa
authors.forename: Ai
authors.initials: A
authors.lastname: Akimoto-Kato
authors.forename: Masashi
authors.initials: M
authors.lastname: Sakuma
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Kuraku
authors.forename: Shigeo
authors.initials: S
authors.lastname: Hayashi
mesh_terms: D000818:Animals; D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics*; D002454:Cell Differentiation; D002455:Cell Division; D049109:Cell Proliferation; D042002:Chromatin Assembly and Disassembly; D016193:G1 Phase; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D011077:Polychaeta / Q000235:genetics* / Q000502:physiology; D012038:Regeneration; D015398:Signal Transduction; D013623:Tail / Q000166:cytology / Q000502:physiology*
keywords: Polychaete; Regeneration; Segmentation; Wingless