Hippocampal pyramidal cells in adult Fmr1 knockout mice exhibit an immature-appearing profile of dendritic spines

Brain Res. 2006 Apr 21;1084(1):158-64. doi: 10.1016/j.brainres.2006.02.044. Epub 2006 Mar 30.


Fragile X syndrome (FXS) is a common form of mental retardation caused by the absence of functional fragile X mental retardation protein (FMRP). FXS is associated with elevated density and length of dendritic spines, as well as an immature-appearing distribution profile of spine morphologies in the neocortex. Mice that lack FMRP (Fmr1 knockout mice) exhibit a similar phenotype in the neocortex, suggesting that FMRP is important for dendritic spine maturation and pruning. Examination of Golgi-stained pyramidal cells in hippocampal subfield CA1 of adult Fmr1 knockout mice reveals longer spines than controls and a morphology profile that, while essentially opposite of that described in the Fmr1 knockout neocortex, appears similarly immature. This finding strongly suggests that FMRP is required for the processes of spine maturation and pruning in multiple brain regions and that the specific pathology depends on the cellular context.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chi-Square Distribution
  • Dendritic Spines / classification
  • Dendritic Spines / physiology*
  • Dendritic Spines / ultrastructure
  • Fragile X Mental Retardation Protein / genetics*
  • Hippocampus / cytology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Pyramidal Cells / physiology
  • Pyramidal Cells / ultrastructure*
  • Silver Staining / methods
  • Visual Cortex / ultrastructure


  • Fmr1 protein, mouse
  • Fragile X Mental Retardation Protein