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Influences on neural lineage and mode of division in the zebrafish retina in vivo.

Poggi L, Vitorino M, Masai I, Harris WA - J. Cell Biol. (2005)

Bottom Line: Proc.Natl.This study provides the first insight into reproducible lineage patterns of retinal progenitors in vivo and the first evidence that environmental signals influence the orientation of cell division and the lineage of neural progenitors.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, University of Cambridge, Cambridge CB2 3DY, United Kingdom.

ABSTRACT
Cell determination in the retina has been under intense investigation since the discovery that retinal progenitors generate clones of apparently random composition (Price, J., D. Turner, and C. Cepko. 1987. Proc. Natl. Acad. Sci. USA. 84:156-160; Holt, C.E., T.W. Bertsch, H.M. Ellis, and W.A. Harris. 1988. Neuron. 1:15-26; Wetts, R., and S.E. Fraser. 1988. Science. 239:1142-1145). Examination of fixed tissue, however, sheds little light on lineage patterns or on the relationship between the orientation of division and cell fate. In this study, three-dimensional time-lapse analyses were used to trace lineages of retinal progenitors expressing green fluorescent protein under the control of the ath5 promoter. Surprisingly, these cells divide just once along the circumferential axis to produce two postmitotic daughters, one of which becomes a retinal ganglion cell (RGC). Interestingly, when these same progenitors are transplanted into a mutant environment lacking RGCs, they often divide along the central-peripheral axis and produce two RGCs. This study provides the first insight into reproducible lineage patterns of retinal progenitors in vivo and the first evidence that environmental signals influence the orientation of cell division and the lineage of neural progenitors.

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ath5:GFP progenitors appear in G2 and divide once, generating one RGC and one non-RGC daughter cell. (A) Time-lapse series showing the lineage of an ath5:GFP progenitor transplanted in a wild-type environment. Imaging was started 30–32 h after fertilization, and t = 0 corresponds to the time of appearance of ath5:GFP (4 h after the onset of the video recording). Daughter cells have been highlighted with different colors (red or yellow). The apical surface is up, whereas the basal surface is down. After division (t = 45 min), both daughter cells migrate toward the basal surface. At t = 5 h, one daughter cell (red) migrates toward the apical surface, whereas the other one (yellow) retracts the apical process and starts to grow an axon toward the basal surface. The white arrows point at the retracting apical process and the growth cone at the tip of the axon. Every single image is a 3D reconstruction of confocal stacks. AP, apical cell; RGC, retinal ganglion cell. (B) Diagram similar to the one shown in Fig. 1 B illustrating this division lineage, which is schematically represented in C.
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fig3: ath5:GFP progenitors appear in G2 and divide once, generating one RGC and one non-RGC daughter cell. (A) Time-lapse series showing the lineage of an ath5:GFP progenitor transplanted in a wild-type environment. Imaging was started 30–32 h after fertilization, and t = 0 corresponds to the time of appearance of ath5:GFP (4 h after the onset of the video recording). Daughter cells have been highlighted with different colors (red or yellow). The apical surface is up, whereas the basal surface is down. After division (t = 45 min), both daughter cells migrate toward the basal surface. At t = 5 h, one daughter cell (red) migrates toward the apical surface, whereas the other one (yellow) retracts the apical process and starts to grow an axon toward the basal surface. The white arrows point at the retracting apical process and the growth cone at the tip of the axon. Every single image is a 3D reconstruction of confocal stacks. AP, apical cell; RGC, retinal ganglion cell. (B) Diagram similar to the one shown in Fig. 1 B illustrating this division lineage, which is schematically represented in C.

Mentions: To map out the lineage relationships between the ath5:GFP-positive RGCs and the other ath5:GFP-positive cells in the retina, we examined the dividing ath5:GFP progenitors and followed their descendents by 3D time lapse. This was difficult to do in the “normal” transgenic fish embryos because the high density of ath5:GFP-positive cells made it difficult to pick out lineages in our time-lapse videos. Therefore, to see these progenitors more clearly, we transplanted blastula-stage cells from ath5:GFP transgenic fish into the blastulas of nontransgenic host embryos. This early stage transplantation ensured that the transgenic cells had fully integrated normally into their wild-type hosts while allowing the density of transgenic cells in the retinas to be low enough for good observation. We then imaged several individual ath5:GFP-expressing progenitors in host retinas starting from 32–35 h after fertilization. We saw no cell deaths in the population of ath5:GFP-positive cells or their progeny within the time period studied (unpublished data). Anaphase and cytokinesis of ath5:GFP progenitors always occurred at the apical surface of the retina and parallel to it, as previously observed for all cell divisions in the zebrafish retina (Das et al., 2003). We were able to trace the GFP label in the daughters of 14 ath5:GFP dividing progenitors for many hours. All ath5:GFP-positive progenitors gave rise to two daughter cells. After separation, the two daughter cells reextended toward the basal surface but then usually migrated in opposite directions and acquired different morphologies. One daughter invariably migrated basally, withdrew its apical process, and began acquiring, through laminar position and axon extension, the characteristics of an RGC. The other daughter withdrew its basal process and migrated back to the apical surface. Fig. 3 shows an example of this lineage pattern (Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200509098/DC1). This apical cell often changed in shape and began to look like an immature photoreceptor. When we tried to track the fate of this cell by extending our video recording, we observed the GFP signal becoming fainter, eventually disappearing from the focal plane. Although we were not able to show a clear fate for the apical daughter cell, our observations indicated that these apical cells did not divide again even within the extended time frame of these recordings, which is consistent with the observations that ath5-positive cells were always BrdU negative (Masai et al., 2005). Thus, the lineage pattern of these ath5:GFP progenitors seems to be reproducibly programmed to give rise to two postmitotic daughters, one of which becomes an RGC.


Influences on neural lineage and mode of division in the zebrafish retina in vivo.

Poggi L, Vitorino M, Masai I, Harris WA - J. Cell Biol. (2005)

ath5:GFP progenitors appear in G2 and divide once, generating one RGC and one non-RGC daughter cell. (A) Time-lapse series showing the lineage of an ath5:GFP progenitor transplanted in a wild-type environment. Imaging was started 30–32 h after fertilization, and t = 0 corresponds to the time of appearance of ath5:GFP (4 h after the onset of the video recording). Daughter cells have been highlighted with different colors (red or yellow). The apical surface is up, whereas the basal surface is down. After division (t = 45 min), both daughter cells migrate toward the basal surface. At t = 5 h, one daughter cell (red) migrates toward the apical surface, whereas the other one (yellow) retracts the apical process and starts to grow an axon toward the basal surface. The white arrows point at the retracting apical process and the growth cone at the tip of the axon. Every single image is a 3D reconstruction of confocal stacks. AP, apical cell; RGC, retinal ganglion cell. (B) Diagram similar to the one shown in Fig. 1 B illustrating this division lineage, which is schematically represented in C.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2171316&req=5

fig3: ath5:GFP progenitors appear in G2 and divide once, generating one RGC and one non-RGC daughter cell. (A) Time-lapse series showing the lineage of an ath5:GFP progenitor transplanted in a wild-type environment. Imaging was started 30–32 h after fertilization, and t = 0 corresponds to the time of appearance of ath5:GFP (4 h after the onset of the video recording). Daughter cells have been highlighted with different colors (red or yellow). The apical surface is up, whereas the basal surface is down. After division (t = 45 min), both daughter cells migrate toward the basal surface. At t = 5 h, one daughter cell (red) migrates toward the apical surface, whereas the other one (yellow) retracts the apical process and starts to grow an axon toward the basal surface. The white arrows point at the retracting apical process and the growth cone at the tip of the axon. Every single image is a 3D reconstruction of confocal stacks. AP, apical cell; RGC, retinal ganglion cell. (B) Diagram similar to the one shown in Fig. 1 B illustrating this division lineage, which is schematically represented in C.
Mentions: To map out the lineage relationships between the ath5:GFP-positive RGCs and the other ath5:GFP-positive cells in the retina, we examined the dividing ath5:GFP progenitors and followed their descendents by 3D time lapse. This was difficult to do in the “normal” transgenic fish embryos because the high density of ath5:GFP-positive cells made it difficult to pick out lineages in our time-lapse videos. Therefore, to see these progenitors more clearly, we transplanted blastula-stage cells from ath5:GFP transgenic fish into the blastulas of nontransgenic host embryos. This early stage transplantation ensured that the transgenic cells had fully integrated normally into their wild-type hosts while allowing the density of transgenic cells in the retinas to be low enough for good observation. We then imaged several individual ath5:GFP-expressing progenitors in host retinas starting from 32–35 h after fertilization. We saw no cell deaths in the population of ath5:GFP-positive cells or their progeny within the time period studied (unpublished data). Anaphase and cytokinesis of ath5:GFP progenitors always occurred at the apical surface of the retina and parallel to it, as previously observed for all cell divisions in the zebrafish retina (Das et al., 2003). We were able to trace the GFP label in the daughters of 14 ath5:GFP dividing progenitors for many hours. All ath5:GFP-positive progenitors gave rise to two daughter cells. After separation, the two daughter cells reextended toward the basal surface but then usually migrated in opposite directions and acquired different morphologies. One daughter invariably migrated basally, withdrew its apical process, and began acquiring, through laminar position and axon extension, the characteristics of an RGC. The other daughter withdrew its basal process and migrated back to the apical surface. Fig. 3 shows an example of this lineage pattern (Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200509098/DC1). This apical cell often changed in shape and began to look like an immature photoreceptor. When we tried to track the fate of this cell by extending our video recording, we observed the GFP signal becoming fainter, eventually disappearing from the focal plane. Although we were not able to show a clear fate for the apical daughter cell, our observations indicated that these apical cells did not divide again even within the extended time frame of these recordings, which is consistent with the observations that ath5-positive cells were always BrdU negative (Masai et al., 2005). Thus, the lineage pattern of these ath5:GFP progenitors seems to be reproducibly programmed to give rise to two postmitotic daughters, one of which becomes an RGC.

Bottom Line: Proc.Natl.This study provides the first insight into reproducible lineage patterns of retinal progenitors in vivo and the first evidence that environmental signals influence the orientation of cell division and the lineage of neural progenitors.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, University of Cambridge, Cambridge CB2 3DY, United Kingdom.

ABSTRACT
Cell determination in the retina has been under intense investigation since the discovery that retinal progenitors generate clones of apparently random composition (Price, J., D. Turner, and C. Cepko. 1987. Proc. Natl. Acad. Sci. USA. 84:156-160; Holt, C.E., T.W. Bertsch, H.M. Ellis, and W.A. Harris. 1988. Neuron. 1:15-26; Wetts, R., and S.E. Fraser. 1988. Science. 239:1142-1145). Examination of fixed tissue, however, sheds little light on lineage patterns or on the relationship between the orientation of division and cell fate. In this study, three-dimensional time-lapse analyses were used to trace lineages of retinal progenitors expressing green fluorescent protein under the control of the ath5 promoter. Surprisingly, these cells divide just once along the circumferential axis to produce two postmitotic daughters, one of which becomes a retinal ganglion cell (RGC). Interestingly, when these same progenitors are transplanted into a mutant environment lacking RGCs, they often divide along the central-peripheral axis and produce two RGCs. This study provides the first insight into reproducible lineage patterns of retinal progenitors in vivo and the first evidence that environmental signals influence the orientation of cell division and the lineage of neural progenitors.

Show MeSH
Related in: MedlinePlus