63 research outputs found
Wnt signal modulates proliferation of spinal cord ependymal cells by promoting morphological change of the source cells
No full textDifferent populations of Wnt-containing vesicles are individually released from polarized epithelial cells
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Identification of the laminar-inducing factor: Wnt-signal from the anterior rim induces correct laminar formation of the neural retina in vitro
No full textAbstractTo study the molecular mechanism that controls the laminar organization of the retina, we utilized reaggregation cultures of dissociated retinal cells prepared from chicken embryos. These cells cannot generate laminated structures by themselves and, instead, form rosettes within the reaggregates. However, the dissociated cells can organize into a correctly laminated structure when cultured in the presence of a putative laminar inducing factor coming from particular tissue or cells, but its molecular identity of this factor has long remained elusive. In this study, we found that the anterior rim of the retina sends a signal to rearrange the rosette-forming cells into a neuroepithelial structure characteristic of the undifferentiated retinal layer. This activity of the anterior rim was mimicked by Wnt-2b expressed in this tissue, and was neutralized by a soluble form of Frizzled, which works as a Wnt antagonist. Furthermore, the neuroepithelial structure induced by Wnt-2b subsequently developed into correctly laminated retinal layers. These observations suggest that the anterior rim functions as a layer-organizing center in the retina, by producing Wnt-2b
Developing a Self-Paced, Web-Based Instructional Module for Dissertation Preparation
No full textAs the number of part-time doctorate students increases, institutions offering evening or online Ph.D. programs need to re-evaluate the effectiveness of their dissertation preparation courses to help these part-time learners succeed. The University of Hawai‘i at Mānoa offers a college-wide Ph.D. in Education with a specialization in Educational Technology (ETEC). The ETEC Ph.D. program is campus-based, but courses are offered in the evenings with many courses offered in hybrid or online formats. ETEC 750e “Educational Technology Issues: Research” is a seminar that ETEC doctoral students must complete before advancing to candidacy and it plays an important role in dissertation preparation. However, due to the number of topics covered in the seminar, instructors have expressed concern over students’ concept attainment of one the seminar topics, prospectus writing. To improve students' prospectus writing skills, the author developed a self-paced, web-based instructional module on prospectus writing to supplement a class lecture, and implemented a formative evaluation to ensure the quality of the module. Five of the eight students enrolled in ETEC 750e in spring 2014 completed the online module, and the data showed a positive shift in their knowledge and attitudes towards prospectus writing. Implications of the project are also discussed
The problem of the assay for tissue plasminogen activator, obtained from various sources, with the fibrin plate method.
No full textRequirement of 19K form of Sonic hedgehog for induction of distinct ventral cell types in CNS explants
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Roles of two types of heparan sulfate clusters in Wnt distribution and signaling in Xenopus
No full textAbstractWnt proteins direct embryonic patterning, but the regulatory basis of their distribution and signal reception remain unclear. Here, we show that endogenous Wnt8 protein is distributed in a graded manner in Xenopus embryo and accumulated on the cell surface in a punctate manner in association with “N-sulfo-rich heparan sulfate (HS),” not with “N-acetyl-rich HS”. These two types of HS are differentially clustered by attaching to different glypicans as core proteins. N-sulfo-rich HS is frequently internalized and associated with the signaling vesicle, known as the Frizzled/Wnt/LRP6 signalosome, in the presence of Wnt8. Conversely, N-acetyl-rich HS is rarely internalized and accumulates Frzb, a secreted Wnt antagonist. Upon interaction with Frzb, Wnt8 associates with N-acetyl-rich HS, suggesting that N-acetyl-rich HS supports Frzb-mediated antagonism by sequestering Wnt8 from N-sulfo-rich HS. Thus, these two types of HS clusters may constitute a cellular platform for the distribution and signaling of Wnt8.</jats:p
Soluble Frizzled-related proteins promote exosome-mediated Wnt re-secretion
No full textAbstract Wnt proteins are thought to be transported in several ways in the extracellular space. For instance, they are known to be carried by exosomes and by Wnt-carrier proteins, such as sFRP proteins. However, little is known about whether and/or how these two transport systems are related. Here, we show that adding sFRP1 or sFRP2, but not sFRP3 or sFRP4, to culture medium containing Wnt3a or Wnt5a increases re-secretion of exosome-loaded Wnt proteins from cells. This effect of sFRP2 is counteracted by heparinase, which removes sugar chains on heparan sulfate proteoglycans (HSPGs), but is independent of LRP5/6, Wnt co-receptors essential for Wnt signaling. Wnt3a and Wnt5a specifically dimerize with sFRP2 in culture supernatant. Furthermore, a Wnt3a mutant defective in heterodimerization with sFRP2 impairs the ability to increase exosome-mediated Wnt3a re-secretion. Based on these results, we propose that Wnt heterodimerization with its carrier protein, sFRP2, enhances Wnt accumulation at sugar chains on HSPGs on the cell surface, leading to increased endocytosis and exosome-mediated Wnt re-secretion. Our results suggest that the range of action of Wnt ligands is controlled by coordination of different transport systems
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