Opposing Morphogenetic Defects on Dendrites and Mossy Fibers of Dentate Granular Neurons in CRMP3-Deficient Mice

Collapsin response mediator proteins (CRMPs) are highly expressed in the brain during early postnatal development and continue to be present in specific regions into adulthood, especially in areas with extensive neuronal plasticity including the hippocampus. They are found in the axons and dendrites of neurons wherein they contribute to specific signaling mechanisms involved in the regulation of axonal and dendritic development/maintenance. We previously identified CRMP3’s role on the morphology of hippocampal CA1 pyramidal dendrites and hippocampus-dependent functions. Our focus here was to further analyze its role in the dentate gyrus where it is highly expressed during development and in adults. On the basis of our new findings, it appears that CRMP3 has critical roles both in axonal and dendritic morphogenesis of dentate granular neurons. In CRMP3-deficient mice, the dendrites become dystrophic while the infrapyramidal bundle of the mossy fiber shows aberrant extension into the stratum oriens of CA3. This axonal misguided projection of granular neurons suggests that the mossy fiber-CA3 synaptic transmission, important for the evoked propagation of the activity of the hippocampal trisynaptic circuitry, may be altered, whereas the dystrophic dendrites may impair the dynamic interactions with the entorhinal cortex, both expected to affect hippocampal function.

Two Types of Spheroid Bodies in the Nigral Neurons in Parkinson's Disease

ABSTRACT:Dendritic spheroid bodies (SBs) and Lewy bodies (LBs) were identified in comparable numbers in the substantia nigra pars compacta (SBC) of nine parkinsonian cases and one case of striatonigral degeneration but were not found irt cases of Huntington's disease or neurologically normal controls. The immunohistochemical profile of the SBs in dystrophic dendrites of nigrostriatal dopaminergic neurons was remarkably similar to that of the LBs found within dendrites or free of the SNC neuropil. Both types of inclusions stained positively with antibodies to tyrosine hydroxylase, ubiquitin and microtubule-associated protein-2 (MAP2), and negatively for Tau-2, although they had different ultrastructural appearances. A few intracellular LBs were stained by antibodies to neurofilament proteins (NFs) 68, 160, and 200 kD, but dendritic SBs and extracellular LBs were not so stained. These data indicate that dendritic SBs and extracellular LBs may have a common molecular pathogenetic origin in Parkinson's disease. On the other hand, the SBs seen in the pars reticulata (SNR) and in the distal nigrostriatal axons even in control cases were generally stained by antibodies to NFs and ubiquitin but not to MAP2. This latter staining pattern in similar to that shown by SBs in the anterior horn in ALS and in the cerebellum of neurologically normal brains and is believed typical of axonal as opposed to dendritic SBs.