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Dorsoventral patterning of the Xenopus eye involves differential temporal changes in the response of optic stalk and retinal progenitors to Hh signalling.

Wang X, Lupo G, He R, Barsacchi G, Harris WA, Liu Y - Neural Dev (2015)

Bottom Line: In loss-of-function assays, inhibition of Hh signalling starting from neurula stages caused expansion of the dorsal retina at the expense of the ventral retina and the optic stalk, while the effects of Hh inhibition during optic vesicle stages were limited to the reduction of optic stalk size.Our results suggest the existence of two competence windows during which the Hh pathway differentially controls patterning of the eye region.We speculate that this temporal regulation is important to coordinate dorsoventral patterning with morphogenesis and differentiation processes during eye development.

View Article: PubMed Central - PubMed

Affiliation: The State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing, 100101, China. 13522764597@163.com.

ABSTRACT

Background: Hedgehog (Hh) signals are instrumental to the dorsoventral patterning of the vertebrate eye, promoting optic stalk and ventral retinal fates and repressing dorsal retinal identity. There has been limited analysis, however, of the critical window during which Hh molecules control eye polarity and of the temporal changes in the responsiveness of eye cells to these signals.

Results: In this study, we used pharmacological and molecular tools to perform stage-specific manipulations of Hh signalling in the developing Xenopus eye. In gain-of-function experiments, most of the eye was sensitive to ventralization when the Hh pathway was activated starting from gastrula/neurula stages. During optic vesicle stages, the dorsal eye became resistant to Hh-dependent ventralization, but this pathway could partially upregulate optic stalk markers within the retina. In loss-of-function assays, inhibition of Hh signalling starting from neurula stages caused expansion of the dorsal retina at the expense of the ventral retina and the optic stalk, while the effects of Hh inhibition during optic vesicle stages were limited to the reduction of optic stalk size.

Conclusions: Our results suggest the existence of two competence windows during which the Hh pathway differentially controls patterning of the eye region. In the first window, between the neural plate and the optic vesicle stages, Hh signalling exerts a global influence on eye dorsoventral polarity, contributing to the specification of optic stalk, ventral retina and dorsal retinal domains. In the second window, between optic vesicle and optic cup stages, this pathway plays a more limited role in the maintenance of the optic stalk domain. We speculate that this temporal regulation is important to coordinate dorsoventral patterning with morphogenesis and differentiation processes during eye development.

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Related in: MedlinePlus

Quantification of gene expression changes following PMP treatments. Real-time PCR quantification of gene expression in st. 33 dissected heads following treatments with 600 μM PMP or DMSO from the indicated stages, shown as the mean ratio between PMP and DMSO conditions in four independent experiments. Error bars show standard deviations. *P < 0.05; **P < 0.01; ***P < 0.001; ns, non-significant (P ≥ 0.05) according to two-tailed Student’s t-test.
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Fig2: Quantification of gene expression changes following PMP treatments. Real-time PCR quantification of gene expression in st. 33 dissected heads following treatments with 600 μM PMP or DMSO from the indicated stages, shown as the mean ratio between PMP and DMSO conditions in four independent experiments. Error bars show standard deviations. *P < 0.05; **P < 0.01; ***P < 0.001; ns, non-significant (P ≥ 0.05) according to two-tailed Student’s t-test.

Mentions: These temporally dependent effects were further characterized by real-time PCR analysis on dissected heads from control and PMP-treated embryos. The Hh pathway direct target genes Ptc1, Ptc2 and Gli1 were significantly upregulated following any PMP treatment condition, suggesting that the different effects of early and late treatments were not due to decreased efficiency of Hh signalling activation (Figure 2). In contrast, Pax2, Vax1b and Vax2 were significantly upregulated by treatments started at st. 8 or st. 13, but not later (Figure 2), confirming that strong ventralization of the dorsal eye requires increased Hh signalling as early as gastrula/neurula stages.Figure 2


Dorsoventral patterning of the Xenopus eye involves differential temporal changes in the response of optic stalk and retinal progenitors to Hh signalling.

Wang X, Lupo G, He R, Barsacchi G, Harris WA, Liu Y - Neural Dev (2015)

Quantification of gene expression changes following PMP treatments. Real-time PCR quantification of gene expression in st. 33 dissected heads following treatments with 600 μM PMP or DMSO from the indicated stages, shown as the mean ratio between PMP and DMSO conditions in four independent experiments. Error bars show standard deviations. *P < 0.05; **P < 0.01; ***P < 0.001; ns, non-significant (P ≥ 0.05) according to two-tailed Student’s t-test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4373414&req=5

Fig2: Quantification of gene expression changes following PMP treatments. Real-time PCR quantification of gene expression in st. 33 dissected heads following treatments with 600 μM PMP or DMSO from the indicated stages, shown as the mean ratio between PMP and DMSO conditions in four independent experiments. Error bars show standard deviations. *P < 0.05; **P < 0.01; ***P < 0.001; ns, non-significant (P ≥ 0.05) according to two-tailed Student’s t-test.
Mentions: These temporally dependent effects were further characterized by real-time PCR analysis on dissected heads from control and PMP-treated embryos. The Hh pathway direct target genes Ptc1, Ptc2 and Gli1 were significantly upregulated following any PMP treatment condition, suggesting that the different effects of early and late treatments were not due to decreased efficiency of Hh signalling activation (Figure 2). In contrast, Pax2, Vax1b and Vax2 were significantly upregulated by treatments started at st. 8 or st. 13, but not later (Figure 2), confirming that strong ventralization of the dorsal eye requires increased Hh signalling as early as gastrula/neurula stages.Figure 2

Bottom Line: In loss-of-function assays, inhibition of Hh signalling starting from neurula stages caused expansion of the dorsal retina at the expense of the ventral retina and the optic stalk, while the effects of Hh inhibition during optic vesicle stages were limited to the reduction of optic stalk size.Our results suggest the existence of two competence windows during which the Hh pathway differentially controls patterning of the eye region.We speculate that this temporal regulation is important to coordinate dorsoventral patterning with morphogenesis and differentiation processes during eye development.

View Article: PubMed Central - PubMed

Affiliation: The State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing, 100101, China. 13522764597@163.com.

ABSTRACT

Background: Hedgehog (Hh) signals are instrumental to the dorsoventral patterning of the vertebrate eye, promoting optic stalk and ventral retinal fates and repressing dorsal retinal identity. There has been limited analysis, however, of the critical window during which Hh molecules control eye polarity and of the temporal changes in the responsiveness of eye cells to these signals.

Results: In this study, we used pharmacological and molecular tools to perform stage-specific manipulations of Hh signalling in the developing Xenopus eye. In gain-of-function experiments, most of the eye was sensitive to ventralization when the Hh pathway was activated starting from gastrula/neurula stages. During optic vesicle stages, the dorsal eye became resistant to Hh-dependent ventralization, but this pathway could partially upregulate optic stalk markers within the retina. In loss-of-function assays, inhibition of Hh signalling starting from neurula stages caused expansion of the dorsal retina at the expense of the ventral retina and the optic stalk, while the effects of Hh inhibition during optic vesicle stages were limited to the reduction of optic stalk size.

Conclusions: Our results suggest the existence of two competence windows during which the Hh pathway differentially controls patterning of the eye region. In the first window, between the neural plate and the optic vesicle stages, Hh signalling exerts a global influence on eye dorsoventral polarity, contributing to the specification of optic stalk, ventral retina and dorsal retinal domains. In the second window, between optic vesicle and optic cup stages, this pathway plays a more limited role in the maintenance of the optic stalk domain. We speculate that this temporal regulation is important to coordinate dorsoventral patterning with morphogenesis and differentiation processes during eye development.

Show MeSH
Related in: MedlinePlus