Functional association of retinoic acid and hedgehog signaling in Xenopus primary neurogenesis

Development ◽  
1999 ◽  
Vol 126 (19) ◽  
pp. 4257-4265 ◽  
Author(s):  
P.G. Franco ◽  
A.R. Paganelli ◽  
S.L. Lopez ◽  
A.E. Carrasco
Keyword(s):  
Retinoic Acid ◽  
Sonic Hedgehog ◽  
Hedgehog Signaling ◽  
Inhibitory Effect ◽  
Neural Plate ◽  
Neural Ectoderm ◽  
Differentiation And Proliferation ◽  
Primary Neurogenesis ◽  
Xenopus Laevis Embryos

Previous work has shown that the posteriorising agent retinoic acid can accelerate anterior neuronal differentiation in Xenopus laevis embryos (Papalopulu, N. and Kintner, C. (1996) Development 122, 3409–3418). To elucidate the role of retinoic acid in the primary neurogenesis cascade, we investigated whether retinoic acid treatment of whole embryos could change the spatial expression of a set of genes known to be involved in neurogenesis. We show that retinoic acid expands the N-tubulin, X-ngnr-1, X-MyT1, X-Δ-1 and Gli3 domains and inhibits the expression of Zic2 and sonic hedgehog in the neural ectoderm, whereas a retinoid antagonist produces opposite changes. In contrast, sonic and banded hedgehog overexpression reduced the N-tubulin stripes, enlarged the neural plate at the expense of the neural crest, downregulated Gli3 and upregulated Zic2. Thus, retinoic acid and hedgehog signaling have opposite effects on the prepattern genes Gli3 and Zic2 and on other genes acting downstream in the neurogenesis cascade. In addition, retinoic acid cannot rescue the inhibitory effect of Notch(ICD), Zic2 or sonic hedgehog on primary neurogenesis. Our results suggest that retinoic acid acts very early, upstream of sonic hedgehog, and we propose a model for regulation of differentiation and proliferation in the neural plate, showing that retinoic acid might be activating primary neurogenesis by repressing sonic hedgehog expression.

scholarly journals The Role of Sonic Hedgehog-Gli2 Pathway in the Masculinization of External Genitalia

Endocrinology ◽  
2011 ◽  
Vol 152 (7) ◽  
pp. 2894-2903 ◽  
Author(s):  
Shinichi Miyagawa ◽  
Daisuke Matsumaru ◽  
Aki Murashima ◽  
Akiko Omori ◽  
Yoshihiko Satoh ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Sonic Hedgehog ◽  
Hedgehog Signaling ◽  
External Genitalia ◽  
Sexually Dimorphic ◽  
Hedgehog Signaling Pathway ◽  
Initial Development ◽  
Urethral Plate ◽  
Male External Genitalia

During embryogenesis, sexually dimorphic organogenesis is achieved by hormones produced in the gonad. The external genitalia develop from a single primordium, the genital tubercle, and their masculinization processes depend on the androgen signaling. In addition to such hormonal signaling, the involvement of nongonadal and locally produced masculinization factors has been unclear. To elucidate the mechanisms of the sexually dimorphic development of the external genitalia, series of conditional mutant mouse analyses were performed using several mutant alleles, particularly focusing on the role of hedgehog signaling pathway in this manuscript. We demonstrate that hedgehog pathway is indispensable for the establishment of male external genitalia characteristics. Sonic hedgehog is expressed in the urethral plate epithelium, and its signal is mediated through glioblastoma 2 (Gli2) in the mesenchyme. The expression level of the sexually dimorphic genes is decreased in the glioblastoma 2 mutant embryos, suggesting that hedgehog signal is likely to facilitate the masculinization processes by affecting the androgen responsiveness. In addition, a conditional mutation of Sonic hedgehog at the sexual differentiation stage leads to abnormal male external genitalia development. The current study identified hedgehog signaling pathway as a key factor not only for initial development but also for sexually dimorphic development of the external genitalia in coordination with androgen signaling.

scholarly journals A critical role of autocrine sonic hedgehog signaling in human CD138+ myeloma cell survival and drug resistance

Blood ◽  
2014 ◽  
Vol 124 (13) ◽  
pp. 2061-2071 ◽  
Author(s):  
Zhiqiang Liu ◽  
Jingda Xu ◽  
Jin He ◽  
Yuhuan Zheng ◽  
Haiyan Li ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Cell Survival ◽  
Sonic Hedgehog ◽  
Hedgehog Signaling ◽  
Critical Role ◽  
Myeloma Cell ◽  
Sonic Hedgehog Signaling ◽  
Key Points

Key Points CD138+ MM cells are a major source of SHH. Autocrine SHH enhances MM drug resistance.

scholarly journals Origins of the avian neural crest: the role of neural plate-epidermal interactions

Development ◽  
1995 ◽  
Vol 121 (2) ◽  
pp. 525-538 ◽  
Author(s):  
M.A. Selleck ◽  
M. Bronner-Fraser
Keyword(s):  
Neural Crest ◽  
Neural Crest Cell ◽  
Neural Crest Cells ◽  
Neural Plate ◽  
Neural Tube Closure ◽  
Whole Embryo Culture ◽  
Early Stages ◽  
Tissue Interactions ◽  
Neural Ectoderm

We have investigated the lineage and tissue interactions that result in avian neural crest cell formation from the ectoderm. Presumptive neural plate was grafted adjacent to non-neural ectoderm in whole embryo culture to examine the role of tissue interactions in ontogeny of the neural crest. Our results show that juxtaposition of non-neural ectoderm and presumptive neural plate induces the formation of neural crest cells. Quail/chick recombinations demonstrate that both the prospective neural plate and the prospective epidermis can contribute to the neural crest. When similar neural plate/epidermal confrontations are performed in tissue culture to look at the formation of neural crest derivatives, juxtaposition of epidermis with either early (stages 4–5) or later (stages 6–10) neural plate results in the generation of both melanocytes and sympathoadrenal cells. Interestingly, neural plates isolated from early stages form no neural crest cells, whereas those isolated later give rise to melanocytes but not crest-derived sympathoadrenal cells. Single cell lineage analysis was performed to determine the time at which the neural crest lineage diverges from the epidermal lineage and to elucidate the timing of neural plate/epidermis interactions during normal development. Our results from stage 8 to 10+ embryos show that the neural plate/neural crest lineage segregates from the epidermis around the time of neural tube closure, suggesting that neural induction is still underway at open neural plate stages.

scholarly journals The Role of Sonic Hedgehog in Human Holoprosencephaly and Short-Rib Polydactyly Syndromes

2021 ◽  
Vol 22 (18) ◽  
pp. 9854
Author(s):  
Christine Loo ◽  
Michael Pearen ◽  
Grant Ramm
Keyword(s):  
Human Development ◽  
Sonic Hedgehog ◽  
Mammalian Cells ◽  
Animal Studies ◽  
Primary Cilia ◽  
Genetic Mutation ◽  
Wide Variability ◽  
Using Data ◽  
Differentiation And Proliferation

The Hedgehog (HH) signalling pathway is one of the major pathways controlling cell differentiation and proliferation during human development. This pathway is complex, with HH function influenced by inhibitors, promotors, interactions with other signalling pathways, and non-genetic and cellular factors. Many aspects of this pathway are not yet clarified. The main features of Sonic Hedgehog (SHH) signalling are discussed in relation to its function in human development. The possible role of SHH will be considered using examples of holoprosencephaly and short-rib polydactyly (SRP) syndromes. In these syndromes, there is wide variability in phenotype even with the same genetic mutation, so that other factors must influence the outcome. SHH mutations were the first identified genetic causes of holoprosencephaly, but many other genes and environmental factors can cause malformations in the holoprosencephaly spectrum. Many patients with SRP have genetic defects affecting primary cilia, structures found on most mammalian cells which are thought to be necessary for canonical HH signal transduction. Although SHH signalling is affected in both these genetic conditions, there is little overlap in phenotype. Possible explanations will be canvassed, using data from published human and animal studies. Implications for the understanding of SHH signalling in humans will be discussed.

Distinct roles for Fgf, Wnt and retinoic acid in posteriorizing the neural ectoderm

Development ◽  
2002 ◽  
Vol 129 (18) ◽  
pp. 4335-4346 ◽  
Author(s):  
Tetsuhiro Kudoh ◽  
Stephen W. Wilson ◽  
Igor B. Dawid
Keyword(s):  
Retinoic Acid ◽  
Neural Plate ◽  
Neural Patterning ◽  
Knock Down ◽  
Complementary Pattern ◽  
Neural Ectoderm ◽  
Morpholino Oligonucleotides ◽  
And Function

Early neural patterning in vertebrates involves signals that inhibit anterior (A) and promote posterior (P) positional values within the nascent neural plate. In this study, we have investigated the contributions of, and interactions between, retinoic acid (RA), Fgf and Wnt signals in the promotion of posterior fates in the ectoderm. We analyze expression and function of cyp26/P450RAI, a gene that encodes retinoic acid 4-hydroxylase, as a tool for investigating these events. Cyp26 is first expressed in the presumptive anterior neural ectoderm and the blastoderm margin at the late blastula. When the posterior neural gene hoxb1b is expressed during gastrulation, it shows a strikingly complementary pattern to cyp26. Using these two genes, as well as otx2 and meis3 as anterior and posterior markers, we show that Fgf and Wnt signals suppress expression of anterior genes, including cyp26. Overexpression of cyp26 suppresses posterior genes, suggesting that the anterior expression of cyp26 is important for restricting the expression of posterior genes. Consistent with this, knock-down of cyp26 by morpholino oligonucleotides leads to the anterior expansion of posterior genes. We further show that Fgf- and Wnt-dependent activation of posterior genes is mediated by RA, whereas suppression of anterior genes does not depend on RA signaling. Fgf and Wnt signals suppress cyp26 expression, while Cyp26 suppresses the RA signal. Thus, cyp26 has an important role in linking the Fgf, Wnt and RA signals to regulate AP patterning of the neural ectoderm in the late blastula to gastrula embryo in zebrafish.

Expression of an engrailed-related protein is induced in the anterior neural ectoderm of early Xenopus embryos

Development ◽  
1989 ◽  
Vol 106 (3) ◽  
pp. 611-617 ◽  
Author(s):  
A.H. Brivanlou ◽  
R.M. Harland
Keyword(s):  
Nuclear Protein ◽  
Neural Plate ◽  
Brain Cells ◽  
Related Protein ◽  
Anterior Portion ◽  
Head Mesoderm ◽  
C Terminus ◽  
Licl Treatment ◽  
Neural Ectoderm ◽  
Xenopus Laevis Embryos

We have used a monoclonal antibody directed against the C-terminus of the Drosophila invected homeodomain to detect a nuclear protein in brain cells of Xenopus laevis embryos. We refer to this antigen as the Xenopus EN protein. The EN protein is localized at midneurula stage to a band of cells in the anterior portion of the neural plate, on each side of the neural groove. Later in development, the expression coincides with the boundary of the midbrain and hindbrain, and persists at least to the swimming tadpole stage. These properties make the EN protein an excellent molecular marker for anterior neural structures. In embryos where inductive interactions between mesodermal and ectodermal tissues have been perturbed, the expression of the EN protein is altered; in embryos that have been anterodorsalized by LiCl treatment, the region that expresses the EN protein is expanded, but still well organized. In ventralized UV-irradiated embryos, the absence of the protein is correlated with the absence of anterior neural structures. In extreme exogastrulae, where the contacts between head mesoderm and prospective neurectoderm are lost, the EN protein is not expressed.

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