Talk:Developmental Signals - Wnt

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On this website the Discussion Tab or "talk pages" for a topic has been used for several purposes: References - recent and historic that relates to the topic Additional topic information - currently prepared in draft format Links - to related webpages Topic page - an edit history as used on other Wiki sites Lecture/Practical - student feedback Student Projects - online project discussions. Links: Pubmed Most Recent | Reference Tutorial | Journal Searches Glossary Links Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link Cite this page: Hill, M.A. (2026, September 19) Embryology Developmental Signals - Wnt. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Talk:Developmental_Signals_-_Wnt

2012

Wnt3 and Wnt3a are required for induction of the mid-diencephalic organizer in the caudal forebrain

Neural Dev. 2012 Apr 4;7:12.

Mattes B, Weber S, Peres J, Chen Q, Davidson G, Houart C, Scholpp S. Source Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), Karlsruhe, Germany. steffen.scholpp@kit.edu.

Abstract

ABSTRACT: BACKGROUND: A fundamental requirement for development of diverse brain regions is the function of local organizers at morphological boundaries. These organizers are restricted groups of cells that secrete signaling molecules, which in turn regulate the fate of the adjacent neural tissue. The thalamus is located in the caudal diencephalon and is the central relay station between the sense organs and higher brain areas. The mid-diencephalic organizer (MDO) orchestrates the development of the thalamus by releasing secreted signaling molecules such as Shh. RESULTS: Here we show that canonical Wnt signaling in the caudal forebrain is required for the formation of the Shh-secreting MD organizer in zebrafish. Wnt signaling induces the MDO in a narrow time window of 4 hours - between 10 and 14 hours post fertilization. Loss of Wnt3 and Wnt3a prevents induction of the MDO, a phenotype also observed upon blockage of canonical Wnt signaling per se. Pharmaceutical activation of the canonical Wnt pathways in Wnt3/Wnt3a compound morphant embryos is able to restore the lack of the MDO. After blockage of Wnt signaling or knock-down of Wnt3/Wnt3a we find an increase of apoptotic cells specifically within the organizer primordium. Consistently, blockage of apoptosis restores the thalamus organizer MDO in Wnt deficient embryos. CONCLUSION: We have identified canonical Wnt signaling as a novel pathway, that is required for proper formation of the MDO and consequently for the development of the major relay station of the brain - the thalamus. We propose that Wnt ligands are necessary to maintain the primordial tissue of the organizer during somitogenesis by suppressing Tp53-mediated apoptosis.

PMID 22475147

2011

Dissecting Molecular Differences between Wnt Coreceptors LRP5 and LRP6

Low-density lipoprotein receptor-related proteins 5 and 6 (LRP5 and LRP6) serve as Wnt co-receptors for the canonical β-catenin pathway. While LRP6 is essential for embryogenesis, both LRP5 and LRP6 play critical roles for skeletal remodeling, osteoporosis pathogenesis and cancer formation, making LRP5 and LRP6 key therapeutic targets for cancer and disease treatment. LRP5 and LRP6 each contain in the cytoplasmic domain five conserved PPPSPxS motifs that are pivotal for signaling and serve collectively as phosphorylation-dependent docking sites for the scaffolding protein Axin. However existing data suggest that LRP6 is more effective than LRP5 in transducing the Wnt signal. To understand the molecular basis that accounts for the different signaling activity of LRP5 and LRP6, we generated a series of chimeric receptors via swapping LRP5 and LRP6 cytoplasmic domains, LRP5C and LRP6C, and studied their Wnt signaling activity using biochemical and functional assays. We demonstrate that LRP6C exhibits strong signaling activity while LRP5C is much less active in cells. Recombinant LRP5C and LRP6C upon in vitro phosphorylation exhibit similar Axin-binding capability, suggesting that LRP5 and LRP6 differ in vivo at a step prior to Axin-binding, likely at receiving phosphorylation. We identified between the two most carboxyl PPPSPxS motifs an intervening “gap4” region that appears to account for much of the difference between LRP5C and LRP6C, and showed that alterations in this region are sufficient to enhance LRP5 PPPSPxS phosphorylation and signaling to levels comparable to LRP6 in cells. In addition we provide evidence that binding of phosphorylated LRP5 or LRP6 to Axin is likely direct and does not require the GSK3 kinase as a bridging intermediate as has been proposed. Our studies therefore uncover a new and important molecular tuning mechanism for differential regulation of LRP5 and LRP6 phosphorylation and signaling activity.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0023537

2010

beta-Catenin regulates intercellular signalling networks and cell-type specific transcription in the developing mouse midbrain-rhombomere 1 region

PLoS One. 2010 Jun 3;5(6):e10881.

Chilov D, Sinjushina N, Saarimäki-Vire J, Taketo MM, Partanen J.

Institute of Biotechnology, University of Helsinki, Helsinki, Finland. Abstract beta-Catenin is a multifunctional protein involved in both signalling by secreted factors of Wnt family and regulation of the cellular architecture. We show that beta-catenin stabilization in mouse midbrain-rhombomere 1 region leads to robust up-regulation of several Wnt signalling target genes, including Fgf8. Suggestive of direct transcriptional regulation of the Fgf8 gene, beta-catenin stabilization resulted in Fgf8 up-regulation also in other tissues, specifically in the ventral limb ectoderm. Interestingly, stabilization of beta-catenin rapidly caused down-regulation of the expression of Wnt1 itself, suggesting a negative feedback loop. The changes in signal molecule expression were concomitant with deregulation of anterior-posterior and dorso-ventral patterning. The transcriptional regulatory functions of beta-catenin were confirmed by beta-catenin loss-of-function experiments. Temporally controlled inactivation of beta-catenin revealed a cell-autonomous role for beta-catenin in the maintenance of cell-type specific gene expression in the progenitors of midbrain dopaminergic neurons. These results highlight the role of beta-catenin in establishment of neuroectodermal signalling centers, promoting region-specific gene expression and regulation of cell fate determination.

PMID: 20532162 http://www.ncbi.nlm.nih.gov/pubmed/20532162

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010881

Wnt1 signaling has been implicated as one factor involved in neural crest-derived melanocyte (NC-M) development. http://www.ncbi.nlm.nih.gov/pubmed/10963668

Neural crest-directed gene transfer demonstrates Wnt1 role in melanocyte expansion and differentiation during mouse development

Proc Natl Acad Sci U S A. 2000 Aug 29;97(18):10050-5. Dunn KJ, Williams BO, Li Y, Pavan WJ.

Genetic Disease Research Branch, National Human Genome Research Institute, and Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4472, USA. Abstract Wnt1 signaling has been implicated as one factor involved in neural crest-derived melanocyte (NC-M) development. Mice deficient for both Wnt1 and Wnt3a have a marked deficiency in trunk neural crest derivatives including NC-Ms. We have used cell lineage-directed gene targeting of Wnt signaling genes to examine the effects of Wnt signaling in mouse neural crest development. Gene expression was directed to cell lineages by infection with subgroup A avian leukosis virus vectors in lines of transgenic mice that express the retrovirus receptor tv-a. Transgenic mice with tva in either nestin-expressing neural precursor cells (line Ntva) or dopachrome tautomerase (DCT)-expressing melanoblasts (line DCTtva) were analyzed. We overstimulated Wnt signaling in two ways: directed gene transfer of Wnt1 to Ntva(+) cells and transfer of beta-catenin to DCTtva(+) NC-M precursor cells. In both methods, NC-M expansion and differentiation were effected. Significant increases were observed in the number of NC-Ms [melanin(+) and tyrosinase-related protein 1 (TYRP1)(+) cells], the differentiation of melanin(-) TYRP1(+) cells to melanin(+) TYRP1(+) NC-Ms, and the intensity of pigmentation per NC-M. These data are consistent with Wnt1 signaling being involved in both expansion and differentiation of migrating NC-Ms in the developing mouse embryo. The use of lineage-directed gene targeting will allow the dissection of signaling molecules involved in NC development and is adaptable to other mammalian developmental systems.

Endothelial specific stabilization of Wnt/beta-catenin signaling alters early vascular development in the embryo by upregulating Dll4/Notch signaling (Dev Cell, June 2010).

Wnt3a deficiency irreversibly impairs hematopoietic stem cell self-renewal and leads to defects in progenitor cell differentiation (Blood, Jan 2009).

The nuclear import of Frizzled2-C by Importins-beta11 and alpha2 promotes postsynaptic development. Therefore, Wnt-activated growth of the post-synaptic membrane is mediated by the synapse-to-nucleus translocation and active nuclear import of Fz2-C (Nat Neurosci, August 2010).