The rodent Four-jointed ortholog Fjx1 regulates dendrite extension

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2007.09.054 Byline: Barbara Probst (a), Rebecca Rock (b), Manfred Gessler (b), Andrea Vortkamp (c), Andreas W. Puschel (a) Keywords: Four-jointed; Dendrite; Hippocampus; Planar cell polarity Abstract: The extrinsic and intrinsic factors that regulate the size and complexity of dendritic arborizations are still poorly understood. Here we identify Fjx1, the rodent ortholog of the Drososphila planar cell polarity (PCP) protein Four-jointed (Fj), as a new inhibitory factor that regulates dendrite extension. The Drosophila gene four-jointed (fj) has been suggested to provide directional information in wing discs, but the mechanism how it acts is only poorly understood and the function of its mammalian homolog Fjx1 remains to be investigated. We analyzed the phenotype of a null mutation for mouse Fjx1. Homozygous Fjx1 mutants show an abnormal morphology of dendritic arbors in the hippocampus. In cultured hippocampal neurons from Fjx1 mutant mice, loss of Fjx1 resulted in an increase in dendrite extension and branching. Addition of Fjx1 to cultures of dissociated hippocampal neurons had the opposite effect and reduced the length of dendrites and decreased dendritic branching. Rescue experiments with cultured neurons showed that Fjx1 can act both cell-autonomously and non-autonomously. Our results identify Fjx1 as a new inhibitory factor that regulates dendrite extension. Author Affiliation: (a) Abteilung Molekularbiologie, Institut fur Allgemeine Zoologie und Genetik, Westfalische Wilhelms-Universitat Munster, SchloAplatz 5, D-48149 Munster, Germany (b) Theodor-Boveri-Institut (Biozentrum), Physiologische Chemie I, Julius-Maximilians-Universitat Wurzburg, Am Hubland, D-97074 Wurzburg, Germany (c) Zentrum fur Medizinische Biotechnologie, Abteilung Entwicklungsbiologie, Universitat Duisburg-Essen, Universitatsstr. D-45117 Essen, Germany Article History: Received 15 August 2007; Revised 24 September 2007; Accepted 25 September 2007