title: The planarian P2X homolog in  the regulation of asexual reproduction.
abstract: The growth in size of freshwater planarians in response to nutrient intake is limited by the eventual separation of tail and body fragments in a process called fission. The resulting tail fragment regenerates the entire body as an artificially amputated tail fragment would do, and the body fragment regenerates a tail, resulting in two whole planarians. This regenerative ability is supported by pluripotent somatic stem cells, called neoblasts, which are distributed throughout almost the entire body of the planarian. Neoblasts are the only planarian cells with the ability to continuously proliferate and give rise to all types of cells during regeneration, asexual reproduction, homeostasis, and growth. In order to investigate the molecular characteristics of neoblasts, we conducted an extensive search for neoblast-specific genes using the High Coverage Expression Profiling (HiCEP) method, and tested the function of the resulting candidates by RNAi. Disruption of the expression of one candidate gene, DjP2X-A (Dugesia japonica membrane protein P2X homologue), resulted in a unique phenotype. DjP2X-A RNAi leads to an increase of fission events upon feeding. We confirmed by immunohistochemistry that DjP2X-A is a membrane protein, and elucidated its role in regulating neoblast proliferation, thereby explaining its unique phenotype. We found that DjP2X-A decreases the burst of neoblast proliferation that normally occurs after feeding. We also found that DjP2X-A is required for normal proliferation in starved animals. We propose that DjP2X-A modulates stem cell proliferation in response to the nutritional condition.
authors.affiliation: Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Sakurai
authors.forename: Hayoung
authors.initials: H
authors.lastname: Lee
authors.forename: Makoto
authors.initials: M
authors.lastname: Kashima
authors.forename: Yumi
authors.initials: Y
authors.lastname: Saito
authors.forename: Tetsutaro
authors.initials: T
authors.lastname: Hayashi
authors.forename: Tomomi
authors.initials: T
authors.lastname: Kudome-Takamatsu
authors.forename: Osamu
authors.initials: O
authors.lastname: Nishimura
authors.forename: Kiyokazu
authors.initials: K
authors.lastname: Agata
authors.forename: Norito
authors.initials: N
authors.lastname: Shibata
mesh_terms: D000818:Animals; D015153:Blotting, Western; D049109:Cell Proliferation; D005247:Feeding Behavior; D015801:Helminth Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D007124:Immunoenzyme Techniques; D010932:Planarians / Q000166:cytology / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012038:Regeneration / Q000502:physiology; D012100:Reproduction, Asexual / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*
chemical_list: D015801:Helminth Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering