title: Inhibitory Smads and bone morphogenetic protein (BMP) modulate anterior photoreceptor cell number during planarian eye regeneration.
abstract: Planarians represent an excellent model to study the processes of body axis and organ re-specification during regeneration. Previous studies have revealed a conserved role for the bone morphogenetic protein (BMP) pathway and its intracellular mediators Smad1/5/8 and Smad4 in planarian dorsoventral (DV) axis re-establishment. In an attempt to gain further insight into the role of this signalling pathway in planarians, we have isolated and functionally characte-rized the inhibitory Smads (I-Smads) in Schmidtea mediterranea. Two I-Smad homologues have been identified: Smed-smad6/7-1 and Smed-smad6/7-2. Expression of smad6/7-1 was detected in the parenchyma, while smad6/7-2 was found to be ex-pressed in the central nervous system and the eyes. Neither single smad6/7-1 and smad6/7-2 nor double smad6/7-1,-2 silencing gave rise to any apparent disruption of the DV axis. However, both regenerating and intact smad6/7-2 (RNAi) planarians showed defects in eye morphogenesis and displayed small, rounded eyes that lacked the anterior subpopulation of photoreceptor cells. The number of pigment cells was also reduced in these animals at later stages of regeneration. In contrast, after low doses of Smed-bmp(RNAi), planarians regenerated larger eyes in which the anterior subpopulation of photoreceptor cells was expanded. Our results suggest that Smed-smad6/7-2 and Smed-bmp control the re-specification and maintenance of anterior photoreceptor cell number in S. mediterranea.
authors.affiliation: Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Barcelona, Catalunya, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: González-Sastre
authors.forename: Ma Dolores
authors.initials: MD
authors.lastname: Molina
authors.forename: Emili
authors.initials: E
authors.lastname: Saló
mesh_terms: D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D005123:Eye / Q000166:cytology* / Q000378:metabolism / Q000528:radiation effects; D017403:In Situ Hybridization; D009416:Nerve Regeneration / Q000502:physiology* / Q000528:radiation effects; D009474:Neurons / Q000166:cytology* / Q000502:physiology / Q000528:radiation effects; D010786:Photoreceptor Cells / Q000166:cytology* / Q000378:metabolism; D010932:Planarians / Q000166:cytology* / Q000502:physiology / Q000528:radiation effects; D012038:Regeneration / Q000502:physiology* / Q000528:radiation effects; D015398:Signal Transduction / Q000528:radiation effects; D051897:Smad Proteins, Inhibitory / Q000378:metabolism*; D014965:X-Rays
chemical_list: D019485:Bone Morphogenetic Proteins; D051897:Smad Proteins, Inhibitory