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  • Title: Altered mossy fiber distributions in adult Fmr1 (FVB) knockout mice.
    Author: Ivanco TL, Greenough WT.
    Journal: Hippocampus; 2002; 12(1):47-54. PubMed ID: 11918288.
    Abstract:
    The fragile-X mental retardation protein (FMRP) is greatly reduced or absent in individuals with fragile-X mental retardation syndrome, a common, heritable form of mental retardation. Morphological studies suggest that this protein functions in normal synapse maturation and neuronal plasticity. Examination of human brain autopsy tissue has shown that fragile-X patients exhibit long, thin spines more frequently, and stubby mushroom-shaped spines less frequently, than these two types of spines are seen in normal autopsy tissue. Fragile-X tissue also has a greater density of these spines along dendrites, which suggests a possible failure of synapse elimination. Fmr1 knockout mice and wild-type littermates brains were processed for Timm staining, which reveals the zinc-rich terminals of the dentate gyrus, the mossy fibers. The Fmr1 knockout mice exhibited a pattern of Timm granule-staining within the stratum oriens of subfield CA3 and the inner molecular layer that was significantly different than staining seen in wild-type animals. The sources and consequences of the altered terminal staining are unclear, but are discussed in relation to immature synapse morphology, a failure of normal regression of synapses, and a potential biological penalty of such a failure to regress.
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