Tubulin and Glial Fibrillary Acidic Protein Gene Expression in Developing Fetal Human Brain at Midgestation

Developmental alterations in the expression of glial fibrillary acidic protein (GFAP) and -tubulin were examined at the level of mRNA and protein in human fetal brain between weeks 13–23 of gestation. Except for a transient increase at week 15, GFAP expression in the cytoskeletal (CSK) fraction was low until week 17, when it increased steadily to week 23, corresponding to the phase of glial proliferation. The developmental profile of -tubulin in the CSK fraction displayed a biphasic pattern, with an initial rise between weeks 13–16 coinciding with the early phase of neuroblast multiplication, and a second rise between weeks 17–23 corresponding to the phase of glial proliferation. No significant difference in the spatial distribution of -tubulin was found in different region of brain but GFAP expression varied with a higher level in cerebellum than that in cerebrum at late midgestation.     

A Time-Dependent Increase in Glial Fibrillary Acidic Protein Expression and Glutamine Synthetase Activity in Long-Term Subculture of the GL15 Glioma Cell Line

1. Astrocytes are the most numerous cellular elements in the central nervous tissue, where they play a critical role in physiological and pathological events. The biological signals regulating astrocyte growth and differentiation are relevant for both physiology and pathology, but they are still little understood.2. Using a poorly differentiated glioma cell line, GL15, we investigated whether, in long-term subculture, this could upregulate the expression of glial fibrillary acidic protein (GFAP), as described in some rodent astrocyte cell lines. Under the same culture conditions, we investigated glutamine synthetase (GS) activity, growth-associated protein (GAP)-43 expression, and expression of several neutrotrophic factors.3. A dramatic increase in GFAP expression was evidenced by Western blotting during progressive in vitro growth of GL15 cells. GS specific activity was also upregulated in long-term culture. The time spent in vitro by GL15 cells did not affect GAP-43 and neutrophic factor BDNF and NT3 expression as revealed by RT-PCR analysis.4. Our results suggest that, in GL15, GFAP and GS genes may have common or integrated regulatory mechanisms elicited at the cell confluency which could be relevant for both astrocyte physiology and astrocyte pathology. These mechanisms are not involved in GAP-43 and neutrophic factor BDNF and NT3 expression.