Gradients in planarian regeneration and homeostasis.
Planarian regeneration was one of the first models in which the gradient concept was developed. Morphological studies based on the analysis of the regeneration rates of planarian fragments from different body regions, the generation of heteromorphoses, and experiments of tissue transplantation led T.H. Morgan (1901) and C.M Child (1911) to postulate different kinds of gradients responsible for the regenerative process in these highly plastic animals. However, after a century of research, the role of morphogens in planarian regeneration has yet to be demonstrated. This may change soon, as the sequencing of the planarian genome and the possibility of performing gene functional analysis by RNA interference (RNAi) have led to the isolation of elements of the bone morphogenetic protein (BMP), Wnt, and fibroblast growth factor (FGF) pathways that control patterning and axial polarity during planarian regeneration and homeostasis. Here, we discuss whether the actions of these molecules could be based on morphogenetic gradients.
Adell
Teresa
T
Department of Genetics and Institute of Biomedicine, University of Barcelona, Av. Diagonal 645, E-08028 Barcelona, Catalonia, Spain.
Cebrià
Francesc
F
Saló
Emili
E
D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D001921:Brain / Q000378:metabolism; D002454:Cell Differentiation; D005346:Fibroblast Growth Factors / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism; D006706:Homeostasis; D008954:Models, Biological; D009474:Neurons / Q000378:metabolism; D010932:Planarians / Q000235:genetics* / Q000502:physiology*; D034622:RNA Interference
D019485:Bone Morphogenetic Proteins; D005346:Fibroblast Growth Factors