title: Sequential implication of the mental retardation proteins ARHGEF6 and PAK3 in spine morphogenesis.
abstract: The biological mechanisms underlying the mental retardation associated with mutation of the ARHGEF6 gene, a Rac1/Cdc42 exchange factor, are still unknown, although defects in the plasticity of synaptic networks have been postulated. We have cloned the rat ARHGEF6 gene and investigated, using a transfection approach, its involvement in spine morphogenesis and its relationship to p21-activated kinase 3 (PAK3). We found that expression of tagged ARHGEF6 in hippocampal slice cultures shows a punctate staining in dendritic spines that colocalizes with PSD95. Over-expression of ARHGEF6, of PAK3 or constitutively active PAK3 did not alter spine morphology. By contrast, knockdown of ARHGEF6 using a siRNA approach resulted in abnormalities in spine morphology similar to those reported with knockdown of PAK3. This phenotype could be rescued through co-expression of a constitutively active PAK3 protein, but not with wild-type PAK3. Together, these results indicate that ARHGEF6 is localized in dendritic spines where it contributes to regulate spine morphogenesis probably by acting through a downstream activation of PAK3. Similar mechanisms are thus likely to underlie the mental retardation induced by mutations of ARHGEF6 and PAK3.
authors.affiliation: Department of Basic Neuroscience, University of Geneva, School of Medicine, 1211 Geneva 4, Switzerland.
authors.forename: Roxanne
authors.initials: R
authors.lastname: Nodé-Langlois
authors.forename: Dominique
authors.initials: D
authors.lastname: Muller
authors.forename: Bernadett
authors.initials: B
authors.lastname: Boda
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D049229:Dendritic Spines / Q000235:genetics* / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D008607:Intellectual Disability / Q000235:genetics; D051379:Mice; D041681:NIH 3T3 Cells; D010641:Phenotype; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D064067:Rho Guanine Nucleotide Exchange Factors; D013997:Time Factors; D046509:Tissue Culture Techniques; D014162:Transfection; D054462:p21-Activated Kinases
chemical_list: C576604:Arhgef6 protein, mouse; D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D034741:RNA, Small Interfering; D064067:Rho Guanine Nucleotide Exchange Factors; C576605:arhgef6 protein, rat; C515912:Pak3 protein, mouse; C515913:Pak3 protein, rat; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases