Spatiotemporal gradient of astrocyte development in the chick optic tectum: evidence for multiple origins and migratory paths of astrocytes.
Astrocytes have been considered to be transformed from radial glial cells that appear at early stage of development and play a scaffold-role for neuronal cell migration. Recent studies indicate that neuroepithelial cells in the spinal cord also give rise to astrocytes. However, the mode of astroglial generation and migration in the ventricular neuroepithelium remains poorly understood. In this study, we have utilized immunohistochemical and retroviral lineage tracing methods to characterize the developmental profiles of astrocytes in the chick optic tectum, which develops from both the neural tube and invasion of optic tract. Chick vimentin and glial fibrillary acidic protein (GFAP) were found as single bands at molecular weights consistent with those reported for mammalian species. Differential developmental trends were observed for both proteins with relative vimentin levels decreasing and GFAP levels increasing with embryonic age. We observed two streams of tectal GFAP-labeled astrocytes originated from the tectal ventricle (intrinsic origin) and the optic tract (extrinsic origin). The extrinsic astrocytes arose from the ventral neuroepithelium of the third ventricle, dispersed bilaterally to the optic tract, and subsequently to the outer layer of optic tectum, indicating migration of astrocytes along retinal ganglion cell axons. On the other hand, the intrinsic astrocytes from the tectal ventricular neuroepithelium appeared first in the ventral part of the optic tectum, and then in the lateral and dorsal tectum. The intrinsic tectal astrocytes closely associated with fascicles of vimentin-labeled radial glial cells, indicating a presumptive radial migration of astrocytes. These results demonstrated that the optic tectum contains heterogeneous populations of astrocytes developed from the different origins and routes of migration.
Seo
Je Hoon
JH
Department of Anatomy, Chungbuk National University College of Medicine, Cheongju 361-763, South Korea.
Chang
Jae Hyuk
JH
Song
Seon Hwa
SH
Lee
Ha Na
HN
Jeon
Gye Sun
GS
Kim
Dong Woon
DW
Chung
Chun Kee
CK
Cho
Sa Sun
SS
D000818:Animals; D001253:Astrocytes / Q000502:physiology*; D001369:Axons / Q000502:physiology; D015153:Blotting, Western; D002465:Cell Movement / Q000502:physiology; D002642:Chick Embryo; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D009457:Neuroglia / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000502:physiology; D012190:Retroviridae / Q000235:genetics; D013477:Superior Colliculi / Q000166:cytology* / Q000254:growth & development*; D014746:Vimentin / Q000378:metabolism
D005904:Glial Fibrillary Acidic Protein; D014746:Vimentin