SURVIVAL OF CAJAL-RETZIUS CELLS AFTER CORTICAL-LESIONS IN NEWBORN MICE - A POSSIBLE ROLE FOR CAJAL-RETZIUS CELLS IN BRAIN REPAIR

Transient Cajal-Retzius (CR) cells in layer I of the mammalian cerebra l cortex are the first postmitotic neurons and they are believed to pl ay a role in neuronal migration and lamination during cortical develop ment. Freezing insults to the cortex of newborn mice produce cortical malformations similar to those observed in human brain disorders. Here we have used calretinin immunostaining to investigate the response of CR cells to freezing lesions of the cortical surface. Shortly after i njury, CR cells disappeared from the lesioned zone. Moreover, CR cells located near the lesioned area adopted extremely fusiform shapes. At later postnatal stages (P12), CR cells were still abundant in layer I of the lesioned zone, in contrast to their almost complete loss in con trol animals. These results show that CR cells survive for longer deve lopmental periods following cortical injury. Furthermore, the initial loss and later re-appearance of CR cells suggest that these neurons mi ght migrate tangentially from the cortical areas surrounding the lesio ned zone. These findings imply a role for CR cells in brain repair aft er cortical injury during development.