Cell migration from the ganglionic eminence to the neocortex investigated by labeling nuclei with UV irradiation via a fiber-optic cable.
Recent studies have shown that the ganglionic eminence is one of the sources of tangentially migrating cells in the developing neocortex. Since the migration of the DiI-labeled cells from the ganglionic eminence to the neocortex was not monitored by videomicroscopy in these reports, we devised a novel method to study cell migration in vitro and in vivo. The new method involves ultraviolet (UV) irradiation of the cells through a fiber-optic cable and subsequent identification of the irradiated cells on the basis of the formation of thymine dimers in the nuclei. First, we tested the new method (UV-thymine dimer-labeling method) by applying it to monitor the cell migration of neuronal precursor cells in the rostral migratory stream in the neonatal rat telencephalon. In vitro, UV irradiation for 1 s through the fiber-optic cable resulted in the formation of sufficient thymine dimers as to allow immunohistochemical detection after 6 h of incubation; a significant proportion of the irradiated cells continued to migrate in the same direction and at the same speed as those before irradiation. There was no significant difference in the cell migration distance over 6 h between cells exposed and not exposed to the UV irradiation in vitro. In vivo, this method revealed that three times as many cells in the subventricular zone of the olfactory bulb migrated rostrally as caudally. The new method also allowed us to measure the speed of cell migration, which was estimated to be about 70 microm/h at the maximum in the rostral direction. After these examinations of reliability of the method, we applied it to the rat embryo brain. One day after UV irradiation of the ganglionic eminence, labeled migrating cells were found in the striatum, in the internal capsule, and in the intermediate zone of the neocortex. The observation period of cell migration to the neocortex was extended by the use of a xeroderma pigmentosum group A gene mutant mouse, which lacked an ability to remove thymine dimer from the UV-irradiated nuclei. Two days after the UV irradiation, labeled migrating cells from the ganglionic eminence of the mutant mouse embryos were found both in the cortical plate and in the intermediate zone of the neocortex.
Tamamaki
N
N
Department of Anatomy, Fukui Medical University, Japan. tamamaki@mbs.med.kyoto-u.ac.jp
Sugimoto
Y
Y
Tanaka
K
K
Takauji
R
R
D000818:Animals; D018929:Cell Culture Techniques; D002465:Cell Movement / Q000502:physiology*; D002467:Cell Nucleus / Q000737:chemistry*; D002540:Cerebral Cortex / Q000166:cytology / Q000196:embryology* / Q000254:growth & development; D005336:Fiber Optic Technology; D051379:Mice; D008817:Mice, Mutant Strains; D009474:Neurons / Q000737:chemistry / Q000166:cytology; D009830:Olfactory Bulb / Q000196:embryology / Q000254:growth & development / Q000601:surgery; D055100:Optical Fibers; D010777:Photochemistry / Q000379:methods; D011740:Pyrimidine Dimers / Q000032:analysis; D051381:Rats; D014466:Ultraviolet Rays
D011740:Pyrimidine Dimers