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Formation and differentiation of the external granular layer of the chick cerebellum
Author(s) -
Hanaway Joseph
Publication year - 1967
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901310102
Subject(s) - granular layer , neuroepithelial cell , cerebellum , anatomy , biology , cerebellar cortex , layer (electronics) , microbiology and biotechnology , neuroscience , materials science , composite material , stem cell , neural stem cell
To examine the formation and differentiation of the external granular layer, chick embryos ranging in age from two to 20 days were treated with tritiated thymidine and sacrificed after various time intervals. By studying the migration of the labeled cells at different stages of development, the following observations were made: (1) cells originating from the neuro‐epithelial layer along the ventricular surface of the cerebellar plate migrate through previously formed cell layers of neuroblasts to the surface; (2) the development of the lateral portion of the cerebellar plate is approximately 24 hours more advanced than that of the medial region, thus explaining the appearance of the external granular layer first laterally and then medially; (3) at no time during development can a proliferation center be found in the ventrolateral angle of the fourth ventricle. Based on theses results, it is concluded that the cells of the external granular layer originate from the neuroepithelium bordering the ventricular surface of the cerebellar plate and migrate from this position straight to the surface. No evidence for a surface migration from the ventrolateral angle in a dorsomedial direction can be found. Shortly after the formation of the external granular layer at day six, its cells begin to proliferate. During this period, which lasts until day 15, relatively few cells leave the external granular layer to migrate inwards. After this day a massive inward migration occurs, and the cells of the external granular layer differentiate into the granular cells and perhaps the glia cells. In the internal granular layer they intermingle with the Purkinje cells and Golgi II neurons, which originate in the neuro‐epithelial layer between days three and six of development. Shortly after hatching, when the external granular layer has fulfilled its function in cell production, it disappears.