Limits...
The prethalamus is established during gastrulation and influences diencephalic regionalization.

Staudt N, Houart C - PLoS Biol. (2007)

Bottom Line: In this study, we draw an extended expression map of the rostral neural plate that reveals discrete domains inside the presumptive posterior forebrain.Finally, transplantation of these precursors, in the rostral-most neural epithelium, induces changes in cell identity in the surrounding host forebrain.This cell-non-autonomous property led us to propose that these committed prethalamic precursors may play an instructive role in the regionalization of the developing diencephalon.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Centre for Developmental Neurobiology, King's College London, London, United Kingdom.

ABSTRACT
The vertebrate neural plate contains distinct domains of gene expression, prefiguring the future brain areas. In this study, we draw an extended expression map of the rostral neural plate that reveals discrete domains inside the presumptive posterior forebrain. We show, by fate mapping, that these well-defined cell populations will develop into specific diencephalic regions. To address whether these early subterritories are already committed to restricted identities, we began to analyse the consequences of ablation and transplantation of these specific cell populations. We found that precursors of the prethalamus are already specified and irreplaceable at late gastrula stage, because ablation of these cells results in loss of prethalamic markers. Moreover, when transplanted into the ectopic environment of the presumptive hindbrain, these cells still pursue their prethalamic differentiation program. Finally, transplantation of these precursors, in the rostral-most neural epithelium, induces changes in cell identity in the surrounding host forebrain. This cell-non-autonomous property led us to propose that these committed prethalamic precursors may play an instructive role in the regionalization of the developing diencephalon.

Show MeSH

Related in: MedlinePlus

Transplantation of Prethalamic Precursors(A) Schematic overview of the transplantation experiment putting prethalamic precursors in ectopic regions of the neural plate.(B–D and H–J) shows dlx2a (blue), tbr1 (red), and transplanted cells in green; (E–G and K–P) shows lhx5 (blue), irx1b (red), and transplanted cells in green.(B–G) Transplanted cells located in the hindbrain show ectopic expression of the prethalamus markers dlx2a (B–D) or lhx5 (E–G); no expression of the telencephalon marker tbr1 (see inset in [B]) could be found in the clone. Cells do not exhibit expression of irx1b (arrow in [F]) in the transplanted cells.(H–P) After transplantation into the forebrain, ectopic cell–non-autonomous expression of dlx2a (arrow in [J]) could be seen (probably resulting in the split of the telencephalon, arrow in [I]) as well as of lhx5 in the thalamus (arrow in [M]). Cells did not switch on the expression of thalamic irx1b (arrow in [O]) in the thalamus.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC1808486&req=5

pbio-0050069-g007: Transplantation of Prethalamic Precursors(A) Schematic overview of the transplantation experiment putting prethalamic precursors in ectopic regions of the neural plate.(B–D and H–J) shows dlx2a (blue), tbr1 (red), and transplanted cells in green; (E–G and K–P) shows lhx5 (blue), irx1b (red), and transplanted cells in green.(B–G) Transplanted cells located in the hindbrain show ectopic expression of the prethalamus markers dlx2a (B–D) or lhx5 (E–G); no expression of the telencephalon marker tbr1 (see inset in [B]) could be found in the clone. Cells do not exhibit expression of irx1b (arrow in [F]) in the transplanted cells.(H–P) After transplantation into the forebrain, ectopic cell–non-autonomous expression of dlx2a (arrow in [J]) could be seen (probably resulting in the split of the telencephalon, arrow in [I]) as well as of lhx5 in the thalamus (arrow in [M]). Cells did not switch on the expression of thalamic irx1b (arrow in [O]) in the thalamus.

Mentions: Having shown that prethalamic identity is already specified at bud stage, we assessed whether this commitment was sufficient to drive the development of these cells into differentiating progenitors. To address this, we tested whether these cells keep their identity and express later prethalamic markers in an ectopic location (Figure 7). Cells of the prethalamic anlage were therefore transplanted into ectopic regions of a host neural plate (Figure 7A). Around 75% of the transplants (n = 28) showed expression of the prethalamic markers dlx2a (Figure 7B–7D and 7H–7J), lhx5 (Figure 7E–7G and 7K–7P), and arx (Figure S1). Because, from late somitogenesis onwards, these markers begin to be expressed in telencephalic progenitors, we analysed, in the same embryos, the expression of bona fide dorsal telencephalic markers tbr1 [27] (Figure 7B–7D and 7H–7J) and emx3 [28] (Figure S1), and show that the transplants acquired diencephalic, but not telencephalic characteristics. When cells are transplanted into the presumptive hindbrain region of the host neural plate (n = 8; Figure 7B–7G) we found expression of both dlx2a (Figure 7B–7D) and lhx5 (Figure 7E–7G) inside the clone and no ectopic expression of the telencephalic markers tbr1 or emx3 (see inset of Figures 7B and S1). The absence of irx1b transcript inside the clones (arrow in Figure 7F) shows that these cells do not express the surrounding hindbrain characteristics. This finding indicates that the transplants develop as prethalamus, showing that these precursors, specified at bud stage, keep their identity independent of their location. In these cases, the transplants form round and compact structures, which are sometimes excluded from the hindbrain (Figure S1). In contrast to these results, donor cells located just rostral to the prethalamic precursors never express prethalamic markers when transplanted in ectopic neural plate areas (n = 7; unpublished data).


The prethalamus is established during gastrulation and influences diencephalic regionalization.

Staudt N, Houart C - PLoS Biol. (2007)

Transplantation of Prethalamic Precursors(A) Schematic overview of the transplantation experiment putting prethalamic precursors in ectopic regions of the neural plate.(B–D and H–J) shows dlx2a (blue), tbr1 (red), and transplanted cells in green; (E–G and K–P) shows lhx5 (blue), irx1b (red), and transplanted cells in green.(B–G) Transplanted cells located in the hindbrain show ectopic expression of the prethalamus markers dlx2a (B–D) or lhx5 (E–G); no expression of the telencephalon marker tbr1 (see inset in [B]) could be found in the clone. Cells do not exhibit expression of irx1b (arrow in [F]) in the transplanted cells.(H–P) After transplantation into the forebrain, ectopic cell–non-autonomous expression of dlx2a (arrow in [J]) could be seen (probably resulting in the split of the telencephalon, arrow in [I]) as well as of lhx5 in the thalamus (arrow in [M]). Cells did not switch on the expression of thalamic irx1b (arrow in [O]) in the thalamus.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1808486&req=5

pbio-0050069-g007: Transplantation of Prethalamic Precursors(A) Schematic overview of the transplantation experiment putting prethalamic precursors in ectopic regions of the neural plate.(B–D and H–J) shows dlx2a (blue), tbr1 (red), and transplanted cells in green; (E–G and K–P) shows lhx5 (blue), irx1b (red), and transplanted cells in green.(B–G) Transplanted cells located in the hindbrain show ectopic expression of the prethalamus markers dlx2a (B–D) or lhx5 (E–G); no expression of the telencephalon marker tbr1 (see inset in [B]) could be found in the clone. Cells do not exhibit expression of irx1b (arrow in [F]) in the transplanted cells.(H–P) After transplantation into the forebrain, ectopic cell–non-autonomous expression of dlx2a (arrow in [J]) could be seen (probably resulting in the split of the telencephalon, arrow in [I]) as well as of lhx5 in the thalamus (arrow in [M]). Cells did not switch on the expression of thalamic irx1b (arrow in [O]) in the thalamus.
Mentions: Having shown that prethalamic identity is already specified at bud stage, we assessed whether this commitment was sufficient to drive the development of these cells into differentiating progenitors. To address this, we tested whether these cells keep their identity and express later prethalamic markers in an ectopic location (Figure 7). Cells of the prethalamic anlage were therefore transplanted into ectopic regions of a host neural plate (Figure 7A). Around 75% of the transplants (n = 28) showed expression of the prethalamic markers dlx2a (Figure 7B–7D and 7H–7J), lhx5 (Figure 7E–7G and 7K–7P), and arx (Figure S1). Because, from late somitogenesis onwards, these markers begin to be expressed in telencephalic progenitors, we analysed, in the same embryos, the expression of bona fide dorsal telencephalic markers tbr1 [27] (Figure 7B–7D and 7H–7J) and emx3 [28] (Figure S1), and show that the transplants acquired diencephalic, but not telencephalic characteristics. When cells are transplanted into the presumptive hindbrain region of the host neural plate (n = 8; Figure 7B–7G) we found expression of both dlx2a (Figure 7B–7D) and lhx5 (Figure 7E–7G) inside the clone and no ectopic expression of the telencephalic markers tbr1 or emx3 (see inset of Figures 7B and S1). The absence of irx1b transcript inside the clones (arrow in Figure 7F) shows that these cells do not express the surrounding hindbrain characteristics. This finding indicates that the transplants develop as prethalamus, showing that these precursors, specified at bud stage, keep their identity independent of their location. In these cases, the transplants form round and compact structures, which are sometimes excluded from the hindbrain (Figure S1). In contrast to these results, donor cells located just rostral to the prethalamic precursors never express prethalamic markers when transplanted in ectopic neural plate areas (n = 7; unpublished data).

Bottom Line: In this study, we draw an extended expression map of the rostral neural plate that reveals discrete domains inside the presumptive posterior forebrain.Finally, transplantation of these precursors, in the rostral-most neural epithelium, induces changes in cell identity in the surrounding host forebrain.This cell-non-autonomous property led us to propose that these committed prethalamic precursors may play an instructive role in the regionalization of the developing diencephalon.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Centre for Developmental Neurobiology, King's College London, London, United Kingdom.

ABSTRACT
The vertebrate neural plate contains distinct domains of gene expression, prefiguring the future brain areas. In this study, we draw an extended expression map of the rostral neural plate that reveals discrete domains inside the presumptive posterior forebrain. We show, by fate mapping, that these well-defined cell populations will develop into specific diencephalic regions. To address whether these early subterritories are already committed to restricted identities, we began to analyse the consequences of ablation and transplantation of these specific cell populations. We found that precursors of the prethalamus are already specified and irreplaceable at late gastrula stage, because ablation of these cells results in loss of prethalamic markers. Moreover, when transplanted into the ectopic environment of the presumptive hindbrain, these cells still pursue their prethalamic differentiation program. Finally, transplantation of these precursors, in the rostral-most neural epithelium, induces changes in cell identity in the surrounding host forebrain. This cell-non-autonomous property led us to propose that these committed prethalamic precursors may play an instructive role in the regionalization of the developing diencephalon.

Show MeSH
Related in: MedlinePlus