Class III β-Tubulin Is Constitutively Coexpressed With Glial Fibrillary Acidic Protein and Nestin in Midgestational Human Fetal Astrocytes: Implications for Phenotypic Identity

Abstract

Class III beta-tubulin isotype (betaIII-tubulin) is widely regarded as a neuronal marker in developmental neurobiology and stem cell research. To test the specificity of this marker protein, we determined its expression and distribution in primary cultures of glial fibrillary acidic protein (GFAP)-expressing astrocytes isolated from the cerebral hemispheres of 2 human fetuses at 18 to 20 weeks of gestation. Cells were maintained as monolayer cultures for 1 to 21 days without differentiation induction. By immunofluorescence microscopy, coexpression of betaIII-tubulin and GFAP was detected in cells at all time points but in spatially distinct patterns. The numbers of GFAP+ cells gradually decreased from Days 1 to 21 in vitro, whereas betaIII-tubulin immunoreactivity was present in 100% of cells at all time points. beta-III-tubulin mRNA and protein expression were demonstrated in cultured cells by reverse-transcriptase-polymerase chain reaction and immunoblotting, respectively. Glial fibrillary acidic protein+/beta-III-tubulin-positive cells coexpressed nestin and vimentin but lacked neurofilament proteins, CD133, and glutamate-aspartate transporter. Weak cytoplasmic staining was detected with antibodies against microtubule-associated protein 2 isoforms. Confocal microscopy, performed on autopsy brain samples of human fetuses at 16 to 20 gestational weeks, revealed widespread colocalization of GFAP and betaIII-tubulin in cells of the ventricular/subventricular zones and the cortical plate. Our results indicate that in the midgestational human brain, betaIII-tubulin is not neuron specific because it is constitutively expressed in GFAP+/nestin+ presumptive fetal astrocytes.

Brain injury activates microglia that induce neural stem cell proliferation ex vivo and promote differentiation of neurosphere-derived cells into neurons and oligodendrocytes

“…what has been observed in the SVZ of human fetuses (Draberova et al, 2008). These data suggest that brain injury could increase the cellular differentiation of NSPCs into neurons and oligodendrocytes.…”

Differentiation of Human Fetal Multipotential Neural Progenitor Cells to Astrocytes Reveals Susceptibility Factors for JC Virus

“…2). Radial glial cells and other GFAP-positive cells can further differentiate into adult neural precursors (27), and midgestational fetal astrocytes can coexpress ␤II-tubulin and GFAP (25). Thus, as human NPCs differentiate in serum toward PDAs, they remain multipotential.…”

“…At 30 days postdifferentiation, a small number of cells expressed the neuronal marker ␤II-tubulin. Almost all cells that express ␤II-tubulin coexpress GFAP, indicating that these may be remaining multipotential cells (25). By 30 days after serum induction, more than 90% of cells expressed GFAP and had an astrocytic morphology.…”

Biological aspects of appendix pathology: irregular distribution of myenteric ganglia in human appendiceal wall

“…Beta III tubulin was found in the central and peripheral nervous systems, and appears to be specifi c for neurons (12,13). However, beta III tubulin was also found in human fetal astrocytes (14). By double labeling, we previously demonstrated a similar staining with both neuronal marker antibodies on non-infl amed appendix cryosections (15).…”