A regulatory role for actin in dendritic spine proliferation

• Published in: Brain research Vol. 1113; no. 1; pp. 1 - 9
• Main Authors: Johnson, Orenda L., Ouimet, Charles C.
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 03-10-2006; Amsterdam Elsevier; New York, NY
• Subjects: Actins - physiology; Acute slice preparation; Animals; Animals, Newborn; Beta-actin; Biolistic gene transfer; Biological and medical sciences; Blotting, Western - methods; Cell Proliferation; Dendrites - ultrastructure; Dendritic Spines - physiology; Dendritic Spines - ultrastructure; Fundamental and applied biological sciences. Psychology; Gene Expression - physiology; Green Fluorescent Proteins - metabolism; Hippocampus; Hippocampus - cytology; Immunohistochemistry - methods; Isolated neuron and nerve. Neuroglia; Male; Microscopy, Confocal - methods; Organ Culture Techniques; Organotypic culture; Overexpression; Presynaptic Terminals - metabolism; Pyramidal Cells - cytology; Pyramidal Cells - ultrastructure; Rats; Silver Staining - methods; Synapsins - metabolism; Time Factors; Transfection - methods; Vertebrates: nervous system and sense organs; Beta-actin; Overexpression; Acute slice preparation; Hippocampus; Organotypic culture; Biolistic gene transfer; Rat; Rodentia; Central nervous system; Encephalon; Vertebrata; Mammalia; Neuron; Actin; Animal; Dendritic spine
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2006.06.116

Dendritic spines are small protrusions that receive 90% of excitatory cortical synapses and are critically important to neural function. Each dendritic spine is supported by a dynamic actin cytoskeleton that responds to internal and external cues to allow spine development, elongation, retraction and movement. Multiple proteins have roles in spinogenesis, but until now, a regulatory role for actin itself has not been established. Here, we show that, in the acute slice preparation, actin expression increases during a period of rapid spinogenesis. Furthermore, actin overexpression in organotypic hippocampal cultures leads to a significant increase in spine density on CA1 pyramidal cells. Specifically, the number of filopodia (long, thin protrusions without heads) increases by 38% on secondary apical dendrites and 88% on basal dendrites and the number of elongated spines with heads increases by 162% on secondary apical dendrites and 113% on basal dendrites. Synapsin-I immunostaining demonstrated that the majority of filopodia and elongated spines are apposed by axon terminals. Additionally, we show that overexpressed actin enters both new and established spines within 24 h. These data demonstrate that neurons undertaking spinogenesis upregulate actin expression, that actin overexpression
per se increases spine density, and that both new and established spines incorporate exogenous actin.