Anat Cell Biol.  2011 Mar;44(1):35-40. 10.5115/acb.2011.44.1.35.

Characterization of the antigenic phenotype of alphaB-crystallin-expressing peripapillary glial cells in the developing chick retina

• Kim JY
• Sohn HJ
• Seo JH

• KMID: 2168866
• DOI: http://doi.org/10.5115/acb.2011.44.1.35

Abstract

Radial glia are transdifferentiated into astrocytes within the developing brain and spinal cord. The neural retina contains Muller cells, which are retinal radial glia. Some of the cells that surround the optic nerve head among Muller cells in the chicken retina are called peripapillary glial cells (PPGCs). PPGCs express different molecules compared to typical Muller cells. However, an antigenic PPGC phenotype has not yet been clearly established. In this study, we classified the antigenic PPGC phenotypes and identified the differentiation stages of these cells. At embryonic day (E)8, alphaB-crystallin-positive PPGCs had a bipolar shape with long processes that traversed entire layers of the retina. Pax2 and vimentin were expressed in alphaB-crystallin-positive PPGCs. Glial fibrillary acidic protein (GFAP) immunoreactivity was not observed in PPGCs. At E18, alphaB-crystallin immunoreactivity disappeared from the vitread processes of PPGCs. However, the PPGC cell bodies and ventricular processes contained alphaB-crystallin protein, and the PPGCs retained the same Pax2-positive/vimentin-positive/GFAP-negative profile as that seen at E8. At post-hatch day 120, alphaB-crystallin and Pax2 immunoreactivity was not observed, but vimentin and GFAP expression was clearly observed in the presumptive location of the PPGCs. Furthermore, these two proteins overlapped within that location. Considering that vimentin expression is prolonged until the post-hatching period in chicken brain, these findings suggest that Pax2-negative/vimentin-positive/GFAP-positive PPGCs are phenotypically identical to mature astrocytes in this avian species.

Keyword

Peripapillary glial cell; alphaB-crystallin; Pax2; Vimentin; Glial fibrillary acidic protein

MeSH Terms

Astrocytes
Brain
Chickens
Glial Fibrillary Acidic Protein
Neuroglia
Optic Disk
Phenotype
Proteins
Retina
Retinaldehyde
Spinal Cord
Vimentin
Glial Fibrillary Acidic Protein
Proteins
Retinaldehyde
Vimentin

Figure

• 

  Fig. 1 αB-crystallin expression in peripapillary glial cells (PPGCs) of developing and adult chicken retinas. (A) Embryonic day (E)8. PPGCs positive for αB-crystallin and that traversed entire layers of the retina were observed between the optic nerve head (ONH) and the retina (arrowheads). (B) E18. αB-crystallin immunoreactivity disappeared in the vitread processes of PPGCs (arrows). Oligodendrocytes positive for αB-crystallin were observed in the ONH and in the nerve fiber layer (NFL) of the retina. (C) Post-hatch day 120 (P120). Although the ONH and the NFL of the retina had weak immunopositive signals, the presumptive location of PPGCs was devoid of αB-crystallin immunoreactivity (arrows). R, retina. Scale bar=20 µm.

• 

  Fig. 2 Pax2, vimentin, and glial fibrillary acidic protein (GFAP) expression in αB-crystallin-positive peripapillary glial cells (PPGCs) in the developing and adult chick retina. (A-C) Embryonic day (E)8. Pax2 (green in A) and vimentin (green in B) immunoreactivities overlapped with αB-crystallin immunoreactivity (red in A and B) in PPGCs. GFAP (green in C) was not expressed in αB-crystallin-positive PPGCs (red in C) in the retina or the optic nerve head (ONH). (D-F) E18. Pax2 (green in D) and vimentin (green in E) were expressed in αB-crystallin-positive PPGCs (red in D and E). A large amount of GFAP (green in F) was expressed in the ONH but not in PPGCs. At this stage, αB-crystallin immunoreactivity was expressed in oligodendrocytes of the ONH and the retina (arrowheads in D-F). (G-I) Post-hatch day 120 (P120). Vimentin and GFAP expression was observed in the presumptive location of PPGCs (dotted areas of G and H). Furthermore, GFAP immunoreactivity overlapped with vimentin immunoreactivity within the same location (dotted area of I). aBC, αB-crystallin; R, retina; Vim, vimentin. Scale bar in C=10 µm (A-C), I=20 µm (D-I).

• 

  Fig. 3 Schematic drawing showing the astrocytic phenotype of αB-crystallin-positive peripapillary glial cells (PPGCs). Lines indicate αB-crystallin-positive PPGCs and dotted lines indicate the presumptive location of PPGCs devoid of αB-crystallin immunoreactivity. At the early stage (embryonic day [E]8), the morphology of αB-crystallin-immunoreactive PPGCs was bipolar with a Pax2-positive/vimentin-positive/glial fibrillary acidic protein (GFAP)-negative phenotype. At the late stage (E18), αB-crystallin immunoreactivity disappeared within the vitread processes of PPGCs, which had the same antigenic phenotype as E8 cells. In the adult retina (post-hatch day 120 [P120]), a number of secondary processes extended from the primary vitread processes of PPGCs to form a densely fibrous triangular area. Mature PPGCs have a Pax2-negative/vimentin-positive/GFAP-positive phenotype. However, αB-crystallin was not expressed in mature PPGCs. BV, blood vessel; ONH, optic nerve head; P, pecten; R, retina; Vim, vimentin.

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