Massive loss of Cajal-Retzius cells does not disrupt neocortical layer order.
Cajal-Retzius (CR) cells, the predominant source of reelin in developing neocortex, are thought to be essential for the inside out formation of neocortical layers. Fate mapping revealed that a large population of neocortical CR cells arises from the cortical hem. To investigate the function of CR cells, we therefore genetically ablated the hem. Neocortical CR cells were distributed beneath the pial surface in control mice, but were virtually absent in hem-ablated mice from embryonic day (E) 10.5 until birth. CR cells derived from other sources did not invade the neocortical primordium to compensate for hem loss. We predicted that neocortical layers would be inverted in hem-ablated animals, as in reeler mice, deficient in reelin signaling. Against expectation, layers showed the standard order. Low levels of reelin in the cortical primordium, or diffusion of reelin from other sites, may have allowed lamination to proceed. Our findings indicate, however, that the sheet of reelin-rich CR cells that covers the neocortical primordium is not required to direct layer order.
Yoshida
Michio
M
Department of Neurobiology, Pharmacology and Physiology, University of Chicago, IL 60637, USA. myoshida@kaiju.medic.kumamoto-u.ac.jp
Assimacopoulos
Stavroula
S
Jones
Kevin R
KR
Grove
Elizabeth A
EA
D000818:Animals; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics / Q000378:metabolism; D002465:Cell Movement; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008818:Mice, Neurologic Mutants; D008822:Mice, Transgenic; D009024:Morphogenesis; D019579:Neocortex / Q000166:cytology* / Q000196:embryology* / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D000091042:Reelin Protein; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
D015816:Cell Adhesion Molecules, Neuronal; D016326:Extracellular Matrix Proteins; D009419:Nerve Tissue Proteins; D000091042:Reelin Protein; C000717128:Reln protein, mouse; D012697:Serine Endopeptidases