Somatosensory cortical barrel dendritic abnormalities in a mouse model of the fragile X mental retardation syndrome

• Published in: Brain research 2003-05, Vol.971 (1), p.83-89
• Main Authors: Galvez, Roberto, Gopal, Anjali R., Greenough, William T.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Chromosome fragility (bloom syndrome, ataxia telangiectasia, fanconi anemia, x-linked mental retardation...); Dendrites - pathology; Dendritic pruning; Development; fmr1; FMRP; Fragile X; Fragile X Mental Retardation Protein; Fragile X Syndrome - pathology; Medical genetics; Medical sciences; Mice; Mice, Knockout; Models, Animal; Nerve Tissue Proteins - deficiency; RNA-Binding Proteins; Somatosensory cortex; Somatosensory Cortex - pathology; Somatosensory Cortex - ultrastructure
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(03)02363-1

The Fragile X mental retardation syndrome is the largest source of inherited mental retardation. The syndrome usually results from the transcriptional silencing of the fragile X mental retardation gene (FMR1). To date the most prominent reported neuronal abnormalities for the fragile X mental retardation syndrome include a higher density of long thin spines similar to those found in sensory deprived and developing tissue, suggesting a possible deficit in pruning of immature spines. Dendrites on spiny stellate cells in the inner 1/3 of the barrel wall in layer IV of the rodent somatosensory cortex have been shown to exhibit developmental pruning similar to that affecting spines. To determine if FMRP plays a role in dendritic development, these neurons were examined in two strains of adult FMRP knockout (FraX) mice. FraX mice in both strains exhibited a greater amount of septa-oriented dendritic material, a morphology consistent with pre-pruning status early in development. This observation suggests that FMRP could be necessary for normal developmentally regulated dendritic pruning.