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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.

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Ablation of Prethalamic Precursors(A–D) barhl2 (red) and her5pac:egfp (green) are shown in (A) wild-type (wt) and (B–D) prethalamus-ablated (abl) embryos 2 h after surgery.(E–G) arx expression at the 12-somite stage and (H–J) prim5 stage in ablated embryos are shown, representing the different ablation types.(K and L) tbr1 is shown in red, and dlx2a in blue; in comparison to the wt (K), the prethalamic expression of dlx2a is reduced in ablated embryos (arrow in [L]).(M and N) foxb1.2 expression at prim 5 shows that mid-diencephalic domains in ablated embryos are not impaired although the expression appears unorganized in the thalamic domain (arrow in [N]).
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pbio-0050069-g006: Ablation of Prethalamic Precursors(A–D) barhl2 (red) and her5pac:egfp (green) are shown in (A) wild-type (wt) and (B–D) prethalamus-ablated (abl) embryos 2 h after surgery.(E–G) arx expression at the 12-somite stage and (H–J) prim5 stage in ablated embryos are shown, representing the different ablation types.(K and L) tbr1 is shown in red, and dlx2a in blue; in comparison to the wt (K), the prethalamic expression of dlx2a is reduced in ablated embryos (arrow in [L]).(M and N) foxb1.2 expression at prim 5 shows that mid-diencephalic domains in ablated embryos are not impaired although the expression appears unorganized in the thalamic domain (arrow in [N]).

Mentions: We focussed our effort on the domain forming the future prethalamus (dark red domain in Figure 4). Cells of this area were ablated by mechanically removing them from the neural plate (see Materials and Methods). To control the specificity of our ablations, we performed RT-PCR on RNA extracted from prethalamic cells (30 embryos ablated). We tested for presence of transcripts of the anterior diencephalic marker barhl2, the telencephalic marker foxg1 [26], and the midbrain marker pax2a. Although barhl2 is readily amplified, neither of the two others is detected (unpublished data). We observed that half of the treated embryos show a reduction or loss of the marker barhl2 (n = 8, Figure 6A–6D) 2 h after suction of the cells. Another set of ablated embryos, fixed at the 10–12-somite stage, shows a complete (3/11) or partial (4/11) loss of the prethalamus marker arx (Figure 6E–6G). Finally, 19 ablated embryos were left to develop to prim5 stage. About a third of these show a dramatic reduction of arx (n = 6/19, Figure 6H–6J). A loss or severe reduction could also be observed with other prethalamic markers such as dlx2a (Figure 6K and 6L). The ablation of the prethalamic precursors does not lead to a loss of thalamic identity (based on foxb1.2 expression at prim5 stage; Figure 6M and 6N). These data demonstrate that ablation of the prethalamic anlage impairs the formation of the prethalamus, therefore strongly suggesting that this area is indeed specified and irreplaceable at that stage.


The prethalamus is established during gastrulation and influences diencephalic regionalization.

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

Ablation of Prethalamic Precursors(A–D) barhl2 (red) and her5pac:egfp (green) are shown in (A) wild-type (wt) and (B–D) prethalamus-ablated (abl) embryos 2 h after surgery.(E–G) arx expression at the 12-somite stage and (H–J) prim5 stage in ablated embryos are shown, representing the different ablation types.(K and L) tbr1 is shown in red, and dlx2a in blue; in comparison to the wt (K), the prethalamic expression of dlx2a is reduced in ablated embryos (arrow in [L]).(M and N) foxb1.2 expression at prim 5 shows that mid-diencephalic domains in ablated embryos are not impaired although the expression appears unorganized in the thalamic domain (arrow in [N]).
© Copyright Policy
Related In: Results  -  Collection

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

pbio-0050069-g006: Ablation of Prethalamic Precursors(A–D) barhl2 (red) and her5pac:egfp (green) are shown in (A) wild-type (wt) and (B–D) prethalamus-ablated (abl) embryos 2 h after surgery.(E–G) arx expression at the 12-somite stage and (H–J) prim5 stage in ablated embryos are shown, representing the different ablation types.(K and L) tbr1 is shown in red, and dlx2a in blue; in comparison to the wt (K), the prethalamic expression of dlx2a is reduced in ablated embryos (arrow in [L]).(M and N) foxb1.2 expression at prim 5 shows that mid-diencephalic domains in ablated embryos are not impaired although the expression appears unorganized in the thalamic domain (arrow in [N]).
Mentions: We focussed our effort on the domain forming the future prethalamus (dark red domain in Figure 4). Cells of this area were ablated by mechanically removing them from the neural plate (see Materials and Methods). To control the specificity of our ablations, we performed RT-PCR on RNA extracted from prethalamic cells (30 embryos ablated). We tested for presence of transcripts of the anterior diencephalic marker barhl2, the telencephalic marker foxg1 [26], and the midbrain marker pax2a. Although barhl2 is readily amplified, neither of the two others is detected (unpublished data). We observed that half of the treated embryos show a reduction or loss of the marker barhl2 (n = 8, Figure 6A–6D) 2 h after suction of the cells. Another set of ablated embryos, fixed at the 10–12-somite stage, shows a complete (3/11) or partial (4/11) loss of the prethalamus marker arx (Figure 6E–6G). Finally, 19 ablated embryos were left to develop to prim5 stage. About a third of these show a dramatic reduction of arx (n = 6/19, Figure 6H–6J). A loss or severe reduction could also be observed with other prethalamic markers such as dlx2a (Figure 6K and 6L). The ablation of the prethalamic precursors does not lead to a loss of thalamic identity (based on foxb1.2 expression at prim5 stage; Figure 6M and 6N). These data demonstrate that ablation of the prethalamic anlage impairs the formation of the prethalamus, therefore strongly suggesting that this area is indeed specified and irreplaceable at that stage.

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