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More is becoming known about so-called noncanonical Wnt pathways that signal independently of beta-catenin. Here we review recent developments in both the functions and mechanisms of noncanonical Wnt signaling. We also discuss some unresolved and vexing questions. How many noncanonical Wnt pathways are there? How extensive are the parallels between(More)
In addition to the canonical Wnt/beta-catenin signaling pathway, at least two noncanonical Wnt/Fz pathways have been described: the planar cell polarity (PCP) pathway in Drosophila [1] and the Wnt/calcium pathway in vertebrate embryos [2]. Recent work suggests that a vertebrate pathway homologous to the PCP pathway acts to regulate the convergent extension(More)
The Ciona notochord displays planar cell polarity (PCP), with anterior localization of Prickle (Pk) and Strabismus (Stbm). We report that a myosin is polarized anteriorly in these cells and strongly colocalizes with Stbm. Disruption of the actin/myosin machinery with cytochalasin or blebbistatin disrupts polarization of Pk and Stbm, but not of myosin(More)
Although cell intercalation driven by non-canonical Wnt/planar cell polarity (PCP) pathway-dependent mediolateral cell polarity is important for notochord morphogenesis, it is likely that multiple mechanisms shape the notochord as it converges and extends. Here we show that the recessive short-tailed Ciona savignyi mutation chongmague (chm) has a novel(More)
Ascidian larvae have a hollow, dorsal central nervous system that shares many morphological features with vertebrate nervous systems yet is composed of very few cells. We show here that a null mutation in the gene dmrt1 in the ascidian Ciona savignyi results in profound abnormalities in the development of the sensory vesicle (brain), as well as other(More)
Here we use in toto imaging together with computational segmentation and analysis methods to quantify the shape of every cell at multiple stages in the development of a simple organ: the notochord of the ascidian Ciona savignyi. We find that cell shape in the intercalated notochord depends strongly on anterior-posterior (AP) position, with cells in the(More)
The relative positions of the brain and mouth are of central importance for models of chordate evolution. The dorsal hollow neural tube and the mouth have often been thought of as developmentally distinct structures that may have followed independent evolutionary paths. In most chordates however, including vertebrates and ascidians, the mouth primordia have(More)
We present a model for the automated segmentation of cells from confocal microscopy volumes of biological samples. The segmentation task for these images is exceptionally challenging due to weak boundaries and varying intensity during the imaging process. To tackle this, a two step pruning process based on the Fast Marching Method is first applied to obtain(More)
Ascidians, such as Ciona, are invertebrate chordates with simple embryonic body plans and small, relatively non-redundant genomes. Ciona genetics is in its infancy compared to many other model systems, but it provides a powerful method for studying this important vertebrate outgroup. Here we give basic methods for genetic analysis of Ciona, including(More)
BACKGROUND In the simple ascidian chordate Ciona, the signaling pathways and gene regulatory networks giving rise to initial notochord induction are largely understood and the mechanisms of notochord morphogenesis are being systematically elucidated. The notochord has generally been thought of as a non-compartmentalized or regionalized organ that is not(More)