A More General Role for the Fragile X Mental Retardation Protein in Pruning of Both Synaptic and Dendritic Processes
These studies demonstrate that while FMRP does not appear to be involved in dendritic maturation it (1) does appear to be necessary for normal developmental dendritic retraction in both somatosensory whisker barrel cortex and olfactory bulb of FraX mice. Further analysis of both normal development and anatomical and metabolic activity in somatosensory whisker barrel cortex using nissl and cytochrome oxidase staining demonstrated; (2) elevated fmr1 expression in WT males during periods of dendritic development and (3) no anatomical or metabolic abnormalities in cortical barrel dimensions of FraX mice. These observations, of elevated fmr1 expression during dendritic development and normal barrel size and metabolic activity, strongly suggest that FMRP does not modulate dendritic pruning via another FMRP induced abnormality; thus suggesting a more direct role for FMRP in regulating dendritic development. Finally spine analysis of adult FraX somatosensory cortical layer V pyramidal neurons revealed (4) increased spine density, increased spine length, more spines with an immature and fewer spines with a mature morphology, consistent with analyses of other cortical regions. These results along with prior anatomical analyses in FraX mice and FXS patients suggest a more general role for FMRP in regulating pruning of both dendritic and synaptic properties in multiple brain regions.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign