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Bilayered Optic Cup Is Defined Anatomically by The View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector 398 ABSTRACTS / Developmental Biology 295 (2006) 393–402 bilayered optic cup is defined anatomically by the presence of 198 the prospective neural retina (NR) in the distal layer and the Characterization of silica spicule formation during the retinal pigmented epithelium (RPE) proximally. Accordingly, resuscitation and in vitro cell culture of molecular markers accompany morphogenesis by restricting Hymeniacidon perleve their expression to definite compartments. For instance, in the Wei Zhang 1, Xupeng Cao 2, Xingju Yu 1 optic cup, the prospective neural retina expresses Chx10, and the 1 Marine Bioproducts Engineering Group, Dalian Institute of RPE, Mitf. However, to facilitate identification of definite events Chemical Physics, Chinese Academy of Sciences, during oculogenesis, there remains a need to identify additional Dalian, China markers of optical development. Thus, we performed here a 2 Graduate School of the Chinese Academy of Sciences, screen for Wnt ligands that are expressed during eye develop- Beijing, China ment. Specifically, we examined the expression of Wnt1, Wnt3, Wnt4-1 and Wnt5A during chick optic vesicles stages up to optic The biogenic silica mineralization in an intertidal marine cup formation. Of these four genes, only Wnt5A was consis- sponge Hymeniacidon perleve (Porifera: Demospongiae) has tently expressed in the dorsal optic cup. Although Wnt1, Wnt3 been investigated during the developmental process over one and Wnt4-1 were present in the developing nervous system, year period and in an in vitro sponge cell culture. Tissue neither was found in the optic vesicle or cup. Wnt5A was first samples of different developmental stages from dormancy to detected at the dorsal region of the RPE at stage HH14. In stages bloom and decline were collected. The structural dimensions HH15 and HH16, its expression domain increased ventrally in and development characteristics of silica spicules were the both nasal and temporal domains. Throughout all these measured. It was found that the dimensional characteristics of stages, the labeling was restricted to the RPE only, and was spicules were restricted by their material properties. The completely absent in the neural retina. Based on these data, we spicule development that was closely linked with the sponge would like to propose Wnt5A as a marker for early dorsal retinal development can be classified as four distinct stages: newly pigmented epithelium. born, growing, maturing and over-matured. In in vitro cell Corresponding author: [email protected]. culture of archaeocyte-dominant cell populations (ADCP), a time-lapse microscopic observation was set up for studying the doi:10.1016/j.ydbio.2006.04.219 spicule formation and cell–spicule interaction over 1 month period. The first spicule appeared on day 10 during the ADCP culture, and the dynamics of spicule formation mimics the 197 spicule development in the field. To understand the molecular Transdifferentiation in Xenopus laevis eye regulation of spicule developments, the silicatein gene, which Alexander S. Jerome, Maria N. Vergara, Katia Del Rio-Tsonis is responsible for the silicification of sponge spicules has been Miami University, Oxford, OH, USA cloned. In both tissues development and cell cultures, the expressions of silicatein are correlated well with the onset and The process of transdifferentiation involves the transforma- growth of spicules; however, the changes in the number of tion of a differentiated cell type into another. During this spicules formed lag behind the silicatein gene expression. process, a cell must lose its phenotype, the characteristics that make it a unique cell type that performs specific functions, and doi:10.1016/j.ydbio.2006.04.221 become ‘‘stem-like’’, being able to proliferate and give rise to different kinds of cells. This outstanding phenomenon occurs under very specific circumstances in vertebrates, and its 199 understanding could have profound implications in the field ram-6 is required for Caenorhabditis elegans male sensory of regenerative and developmental biology. The eye of the rays morphogenesis Xenopus laevis tadpole provides a good model to analyze this H.Y. Lee, Y.M. Lam, S.W. Tsang, K.L. Chow process. In the present study, we have characterized the process Hong Kong University of Science and Technology, Hong Kong of transdifferentiation of pigmented eye tissues in Xenopus tadpoles, at a stage in which the eye is already fully developed. Caenorhabditis elegans males develop nine pairs of Our aim is to establish a model that will allow for the study of bilaterally symmetrical peripheral sensory organs known as the molecular mechanisms that drive the process of transdiffer- rays. Although they are all morphologically and positionally entiation. We have been able to induce the transdifferentiation distinguishable, each of them develop smooth boundary against of pigmented epithelium explants into lens when transplanted the cuticular fan structure. We are interested in a class of into host Xenopus eyes. In addition, we have induced retina ‘‘ram’’ genes essential for the morphogenesis of these sensory regeneration from pigmented tissues after complete removal of rays. A new component, designated as ram-6, was identified in the retina in vivo. We have also assessed the influence of an EMS mutagenesis screen. ram-6 mutants display severe several growth factors and morphogens on this process. swollen rays phenotype in all of the rays and was shown to complement all other known ram genes. Temperature shift doi:10.1016/j.ydbio.2006.04.220 experiments suggested that ram-6 participates not just in ray development but also in early embryonic development. Mutant ABSTRACTS / Developmental Biology 295 (2006) 393–402 399 embryos often display abnormal cell division with a skewed 201 division plane. As a result, elongated but arrested early Characterization of cuticular collagen gene ram-2 in embryos were observed. In the same screen, a temperature sensory ray morphogenesis sensitive allele, ram(wx72ts), was isolated. ram(wx72ts) does C.N. Tam, W.S. Hui, K.L. Chow not complement ram-6(wx66) and was mapped to same narrow Hong Kong University of Science and Technology, Hong Kong overlapping region of ram-6(wx66), suggesting that they are allelic. Temperature shift experiment with ram(wx72ts) defines Cuticular collagens make up a large protein family in C. the functional requirement at an overlapping developmental elegans. Recently, we have identified three cuticular collagen window as the other ram genes. Genetic mapping and SNP genes, mutations of which display only abnormal morphology mapping located ram-6 on the right arm of chromosome V of the sensory rays. We report here the characterization of ram- leading to our successful rescue of ram-6 mutants by YAC 2, its possible role and transcription regulation in sensory ray microinjection. Experiments are currently underway to molec- morphogenesis. RAM-2 is required for the anterior dorsal ularly characterize ram-6 and to dissect its role in sensory rays migration of the ray cells as shown in the mutants of 3 morphogenesis. (This study is funded by the Research Grants available alleles. Based on the RNAi phenotype and Df Council, Hong Kong.) mapping, bx32 allele behaves as a temperature sensitive dominant negative allele. Since different collagen encoding doi:10.1016/j.ydbio.2006.04.222 ram genes display non-allelic non-complementation property, it is possible that they may be partners constituting the same collagen triplex. ram-2 expression is initially observed in 6 200 hypodermal nuclei ventral to the male tail seam. The Enhanced BMP signaling through a type I BMP receptor expression declines upon reaching adulthood. Since the ALK2 shows ectopic cartilage formation in mouse temporal expression of ram-2 overlaps with the ray formation craniofacial portion period, we delineate its transcriptional regulation and screen for 1 1 1 Yoshihiro Komatsu , Tomokazu Fukuda , Gregory Scott , transcriptional regulator controlling the initiation of ray 1 2 1 Nobuhiro Kamiya , Ken-ichi Yamamura , Yuji Mishina morphogenesis. Promoter deletion analysis of using reporter 1 Laboratory of Reproductive and Developmental Toxicology, marker and cDNA rescue assays identified two essential cis- National Institute of Environmental Health Sciences/NIH, elements within 50 bp consisting of a GATA binding site. Research Triangle Park, USA Subsequently, three potential candidate genes regulating the 2 Institute of Molecular Embryology and Genetics, ram-2 transcription were identified in a genetic screen. The Kumamoto University, Kumamoto, Japan biological significance will be discussed. (The research is funded by Research Grants Council, Hong Kong.) ALK2 (also known as AVCRl or ActRl) is one of the BMP type I receptor and has important roles during mouse doi:10.1016/j.ydbio.2006.04.224 embryogenesis as shown by loss of function studies. However, gain of function studies for ALK2 signals have not been carried out in the mouse to address its sufficiency among develop- 202 mental procedures. To avoid the potential lethality caused by Twisted gastrulation (Twsg1) is critical for the overdose of BMP signaling, we employed the Cre-loxP system morphogenesis of the medial region of the mandibular arch to establish a transgenic mouse that can conditionally express a Anna Petryk 1, Michael P. Jarcho 1, Nick Lowe 1, Mina Mina 2, constitutively active
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