page_title: Reeler
section_title: Key pathological findings in the Reeler brain structure
hierarchical_section_title: Reeler / Key pathological findings in the Reeler brain structure
caption_attribution_description: Corticogenesis in a brain of a mouse. Six cortical layers.
context_page_description: A reeler is a mouse mutant, so named because of its characteristic "reeling" gait. This is caused by the profound underdevelopment of the mouse's cerebellum, a segment of the brain responsible for locomotion. The mutation is autosomal and recessive, and prevents the typical cerebellar folia from forming.
  Cortical neurons are generated normally but are abnormally placed, resulting in disorganization of cortical laminar layers in the central nervous system. The reason is the lack of Reelin, an extracellular matrix glycoprotein, which, during the corticogenesis, is secreted mainly by the Cajal-Retzius cells.
  In the reeler neocortex, cortical plate neurons are aligned in a practically inverted fashion. In the ventricular zone of the cortex fewer neurons have been found to have radial glial processes. In the dentate gyrus of hippocampus, no characteristic radial glial scaffold is formed and no compact granule cell layer is established. Therefore, the reeler mouse presents a good model in which to investigate the mechanisms of establishment of the precise neuronal network during development.
context_section_description: Inversion of cortical layers.
  Subplate cells become abnormally located in the subpial zone above the cortical plate. This hampers their function in establishing the transient circuits between the incoming thalamic axons and layer IV cells of the cortical plate. Thalamic axons have to grow past the cortical plate to reach the mispositioned subplate cells in the so-called superplate and then turn back down to contact their appropriate targets. This creates a curious "looping" thalamocortical connection seen in the adult reeler brain.
  Dispersion of neurons within cortical layers.
  Decreased cerebellar size.
  Failure of preplate to split
  Failure to establish a distinct granule cell layer in the dentate gyrus. Normal dentate gyrus demonstrates a clear segregation of granule cells and hilar mossy cells, which are identified, respectively, by their expression of calbindin and calretinin. In the reeler DG, the two cell types intermingle.
  Impaired dendrite outgrowth.
  In one study, reeler mice were shown to have attenuated methamphetamine-induced hyperlocomotion, which was also reduced by a targeted disruption of reelin activity in wildtype mice. Reeler mice in the same study demonstrated a decrease in D1 and D2 receptor-mediated dopaminergic function together with reduced numbers of D1\D2 receptors.
caption: Corticogenesis in a wild-type mouse. First neurons to take their place are the subplate neurons (yellow). Next come the cortical plate neurons (black), which migrate past the subplate level. Later-generated neurons drawn to be increasingly more bright.
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