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ABSTRACT: Enhancers are flexible in terms of their location and orientation relative to the genes they regulate. However, little is known about whether the flexibility can be applied in every combination of enhancers and genes. Enhancer detection with transposable elements is a powerful method to identify enhancers in the genome and to create marker lines expressing fluorescent proteins in a tissue-specific manner. In the chordate Ciona intestinalis, this method has been established with a Tc1/mariner superfamily transposon Minos. Previously, we created the enhancer detection line E[MiTSAdTPOG]15 (E15) that specifically expresses green fluorescent protein (GFP) in the central nervous system (CNS) after metamorphosis. In this study, we identified the causal insertion site of the transgenic line. There are two genes flanking the causal insertion of the E15 line, and the genomic region around the insertion site contains the enhancers responsible for the expression in the endostyle and gut in addition to the CNS. We found that the endostyle and gut enhancers show sensitivity to the orientation of the GFP gene for their enhancer activity. Namely, the enhancers cannot enhance the expression of GFP which is inserted at the same orientation as the E15 line, while the enhancers can enhance GFP expression inserted at the opposite orientation. The CNS enhancer can enhance GFP expression in both orientations. The DNA element adjacent to the endostyle enhancer is responsible for the orientation sensitivity of the enhancer. The different sensitivity of the enhancers to the orientation of the transgene is a cause of CNS-specific GFP expression in the E15 line.
Developmental Biology 12/2012; · 4.07 Impact Factor
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ABSTRACT: The retina of craniates/vertebrates has been proposed to derive from a photoreceptor prosencephalic territory in ancestral chordates, but the evolutionary origin of the different cell types making the retina is disputed. Except for photoreceptors, the existence of homologs of retinal cells remains uncertain outside vertebrates.
The expression of genes expressed in the sensory vesicle of the ascidian Ciona intestinalis including those encoding components of the monoaminergic neurotransmission systems, was analyzed by in situ hybridization or in vivo transfection of the corresponding regulatory elements driving fluorescent reporters. Modulation of photic responses by monoamines was studied by electrophysiology combined with pharmacological treatments.
We show that many molecular characteristics of dopamine-synthesizing cells located in the vicinity of photoreceptors in the sensory vesicle of the ascidian Ciona intestinalis are similar to those of amacrine dopamine cells of the vertebrate retina. The ascidian dopamine cells share with vertebrate amacrine cells the expression of the key-transcription factor Ptf1a, as well as that of dopamine-synthesizing enzymes. Surprisingly, the ascidian dopamine cells accumulate serotonin via a functional serotonin transporter, as some amacrine cells also do. Moreover, dopamine cells located in the vicinity of the photoreceptors modulate the light-off induced swimming behavior of ascidian larvae by acting on alpha2-like receptors, instead of dopamine receptors, supporting a role in the modulation of the photic response. These cells are located in a territory of the ascidian sensory vesicle expressing genes found both in the retina and the hypothalamus of vertebrates (six3/6, Rx, meis, pax6, visual cycle proteins).
We propose that the dopamine cells of the ascidian larva derive from an ancestral multifunctional cell population located in the periventricular, photoreceptive field of the anterior neural tube of chordates, which also gives rise to both anterior hypothalamus and the retina in craniates/vertebrates. It also shows that the existence of multiple cell types associated with photic responses predates the formation of the vertebrate retina.
BMC Biology 05/2012; 10:45. · 5.75 Impact Factor
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ABSTRACT: Retinoic acid (RA)-mediated expression of the homeobox gene Hox1 is a hallmark of the chordate central nervous system (CNS). It has been suggested that the RA-Hox1 network also functions in the epidermal ectoderm of chordates. Here, we show that in the urochordate ascidian Ciona intestinalis, RA-Hox1 in the epidermal ectoderm is necessary for formation of the atrial siphon placode (ASP), a structure homologous to the vertebrate otic placode. Loss of Hox1 function resulted in loss of the ASP, which could be rescued by expressing Hox1 in the epidermis. As previous studies showed that RA directly upregulates Hox1 in the epidermis of Ciona larvae, we also examined the role of RA in ASP formation. We showed that abolishment of RA resulted in loss of the ASP, which could be rescued by forced expression of Hox1 in the epidermis. Our results suggest that RA-Hox1 in the epidermal ectoderm played a key role in the acquisition of the otic placode during chordate evolution.
Development 05/2012; 139(12):2156-60. · 6.60 Impact Factor
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ABSTRACT: The swimming larvae of the chordate ascidians possess a dorsal hollowed central nervous system (CNS), which is homologous to that of vertebrates. Despite the homology, the ascidian CNS consists of a countable number of cells. The simple nervous system of ascidians provides an excellent experimental system to study the developmental mechanisms of the chordate nervous system. The neural fate of the cells consisting of the ascidian CNS is determined in both autonomous and non-autonomous fashion during the cleavage stage. The ascidian neural plate performs the morphogenetic movement of neural tube closure that resembles that in vertebrate neural tube formation. Following neurulation, the CNS is separated into five distinct regions, whose homology with the regions of vertebrate CNS has been discussed. Following their larval stage, ascidians undergo a metamorphosis and become sessile adults. The metamorphosis is completed quickly, and therefore the metamorphosis of ascidians is a good experimental system to observe the reorganization of the CNS during metamorphosis. A recent study has shown that the major parts of the larval CNS remain after the metamorphosis to form the adult CNS. In contrast to such a conserved manner of CNS reorganization, most larval neurons disappear during metamorphosis. The larval glial cells in the CNS are the major source for the formation of the adult CNS, and some of the glial cells produce adult neurons.
Embryologia 04/2012; 54(3):420-37. · 2.21 Impact Factor
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ABSTRACT: The tunicate Ciona intestinalis larva has a simple central nervous system (CNS), consisting of fewer than 400 cells, which is homologous to the vertebrate CNS. Recent studies have revealed neuronal types and networks in the larval CNS of C. intestinalis, yet their cell lineage and the molecular mechanism by which particular types of neurons are specified and differentiate remain poorly understood. Here, we report cell lineage origin and a cis-regulatory module for the anterior caudal inhibitory neurons (ACINs), a putative component of the central pattern generator regulating swimming locomotion. The vesicular GABA⁄ glycine transporter gene Ci-VGAT, a specific marker for GABAergic ⁄ glycinergic neurons, is expressed in distinct sets of neurons, including ACINs of the tail nerve cord and others in the brain vesicle and motor ganglion. Comparative genomics analysis between C. intestinalis and Ciona savignyi and functional analysis in vivo identified the cis-regulatory module responsible for Ci-VGAT expression in ACINs. Our cell lineage analyses inferred that ACINs derive from A11.116 cells, which have been thought to solely give rise to glial ependymal cells of the lateral wall of the nerve cord. The present findings will provide a solid basis for future studies addressing the molecular mechanism underlying specification of ACINs, which play a critical role in controlling larval locomotion
Embryologia 02/2012; 54(2):177-86. · 2.21 Impact Factor
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ABSTRACT: In ascidian tunicates, the metamorphic transition from larva to adult is accompanied by dynamic changes in the body plan. For instance, the central nervous system (CNS) is subjected to extensive rearrangement because its regulating larval organs are lost and new adult organs are created. To understand how the adult CNS is reconstructed, we traced the fate of larval CNS cells during ascidian metamorphosis by using transgenic animals and imaging technologies with photoconvertible fluorescent proteins. Here we show that most parts of the ascidian larval CNS, except for the tail nerve cord, are maintained during metamorphosis and recruited to form the adult CNS. We also show that most of the larval neurons disappear and only a subset of cholinergic motor neurons and glutamatergic neurons are retained. Finally, we demonstrate that ependymal cells of the larval CNS contribute to the construction of the adult CNS and that some differentiate into neurons in the adult CNS. An unexpected role of ependymal cells highlighted by this study is that they serve as neural stem-like cells to reconstruct the adult nervous network during chordate metamorphosis. Consequently, the plasticity of non-neuronal ependymal cells and neuronal cells in chordates should be re-examined by future studies.
Nature 01/2011; 469(7331):525-8. · 36.28 Impact Factor
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ABSTRACT: Despite containing only approximately 330 cells, the central nervous system (CNS) of Ciona intestinalis larvae has an architecture that is similar to the vertebrate CNS. Although only vertebrates have a distinct hypothalamus-the source of numerous neurohormone peptides that play pivotal roles in the development, function, and maintenance of various neuronal and endocrine systems, it is suggested that the Ciona brain contains a region that corresponds to the vertebrate hypothalamus. To identify genes expressed in the brain, we isolated brain vesicles using transgenic embryos carrying Ci-β-tubulin(promoter)::Kaede, which resulted in robust Kaede expression in the larval CNS. The associated transcriptome was investigated using microarray analysis. We identified 565 genes that were preferentially expressed in the larval brain. Among these genes, 11 encoded neurohormone peptides including such hypothalamic peptides as gonadotropin-releasing hormone and oxytocin/vasopressin. Six of the identified peptide genes had not been previously described. We also found that genes encoding receptors for some of the peptides were expressed in the brain. Interestingly, whole-mount in situ hybridization showed that most of the peptide genes were expressed in the ventral brain. This catalog of the genes expressed in the larval brain should help elucidate the evolution, development, and functioning of the chordate brain.
Developmental Biology 01/2011; 352(2):202-14. · 4.07 Impact Factor
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ABSTRACT: The adult of the ascidian Ciona intestinalis has cupular organs, i.e., putative hydrodynamic sensors, at the atrial epithelium. The cupular organ consists of support cells and sensory neurons, and it extends a gelatinous matrix, known as a cupula, toward the atrial cavity. These characteristics are shared with sensory hair cells in the vertebrate inner ear and lateral line neuromasts in fish and amphibians, which suggests an evolutionary link between the cupular organ and these vertebrate hydrodynamic sensors. In the present study, we have isolated and investigated two transposon-mediated enhancer detection lines that showed GFP expression in support cells of the cupular organs. Using the enhancer detection lines and neuron marker transgenic lines, we describe the position, morphology, and development of the cupular organs. Cupular organs were found at the atrial epithelium, but not in the branchial epithelium. We found that cupular organs are also present along the dorsal fold and the gonoducts. The cells lining the pre-atrial opening in juveniles are presumably precursor cells of the cupular organ. To our knowledge, the present study is the first precise description of the ascidian cupular organ, providing evidence that may help to resolve discrepancies among previous studies on the organ.
ZOOLOGICAL SCIENCE 11/2010; 27(11):842-50. · 0.95 Impact Factor
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Developmental Biology 08/2010; 344(1):529. · 4.07 Impact Factor
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ABSTRACT: In ascidian Ciona intestinalis, a subset of trunk epidermal neurons were shown to possess external network of neural projections. To characterize a more complete network in naturally hatched (chorionated) larvae, we visualized the structure with a confocal laser scanning microscope. High resolution images revealed the huge network consisting of several subnetworks in whole-larval tunic. We named this network the ASNET (ascidian dendritic network in tunic). The ASNET was dynamically generated and collapsed during larval stages. Interestingly, one of the subnetworks found around apical trunk epidermal neurons was bilaterally asymmetric. In caudal epidermal neurons, transmission electron microscopy revealed that 9+2 axonemes were accompanied by a vesicle-containing mass in the ASNET arbor, but the distal end of the arbor contained only the vesicle-containing fibrous mass and no 9+2 axonemes. The characteristics of the ASNET suggest that it forms a unique outer body network in the ascidian larval tunic.
Developmental Dynamics 08/2010; 239(8):2278-87. · 2.54 Impact Factor
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ABSTRACT: 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 anterior ectodermal derivatives, including the palps and oral siphon primordium (OSP). Although the phenotype of the mutant embryos is variable, the majority have a complete loss of the most anterior structures (palps and OSP) and extensive disruption of sensory structures, such as the light-sensitive ocellus, in the sensory vesicle. dmrt1 is expressed early in the blastula embryo in a small group of presumptive ectodermal cells as they become restricted to anterior neural, OSP and palp fates. Despite the early and restricted expression of dmrt1, we were unable, using several independent criteria, to observe a defect in the mutant embryos until the early tailbud stage. We speculate that the variability and late onset in the phenotype may be due to partially overlapping activities of other gene products.
Development 07/2010; 137(13):2197-203. · 6.60 Impact Factor
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ABSTRACT: The ascidian larva is an excellent model for studies of the functional organization and neuronal circuits of chordates due to its remarkably simple central nervous system (CNS), comprised of about 100 neurons. To date, however, the identities of the various neurons in the ascidian larva, particularly their neurotransmitter phenotypes, are not well established. Acetylcholine, GABA, and glycine are critical neurotransmitters for locomotion in many animals. We visualized putative cholinergic neurons and GABAergic/glycinergic neurons in the ascidian larva by immunofluorescent staining using antibodies against vesicular acetylcholine transporter (VACHT) and vesicular GABA/glycine transporter (VGAT), respectively. Neurons expressing a cholinergic phenotype were found in the brain vesicle and the visceral ganglion. Five pairs of VACHT-positive neurons were located in the visceral ganglion. These putative cholinergic neurons extended their axons posteriorly and formed nerve terminals proximal to the most anterior muscle cells in the tail. VGAT-positive neurons were located in the brain vesicle, the visceral ganglion, and the anterior nerve cord. Two distinct pairs of VGAT-positive neurons, bilaterally aligned along the anterior nerve cord, extended axons anteriorly, near to the axons of the contralateral VACHT-positive neurons. Cell bodies of the VGAT-positive neurons lay on these nerve tracts. The neuronal complex, comprising motor neurons with a cholinergic phenotype and some of the GABA/glycinergic interneurons, has structural features that are compatible with a central pattern generator (CPG) producing a rhythmic movement of the tail. The simple CPG of the ascidian larva may represent the ancestral state of the vertebrate motor system.
ZOOLOGICAL SCIENCE 02/2010; 27(2):181-90. · 0.95 Impact Factor
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ABSTRACT: Accumulating evidence demonstrates that cilia play important roles in a variety of processes in embryogenesis. For functional survey of larval cilia at the cellular level, we exploited the simple cell organization of tadpole larvae in the ascidian Ciona intestinalis. Immunofluorescent microscopy showed distribution of cilia not only in previously described tissues but also in a subpopulation of ependymal cells in the sensory vesicle, gut primordium, papillae, apical trunk epidermal neurons, and the endodermal strand. Transmission electron microscopy revealed a variety of axonemal structures, including a 9+0 structure similar to vertebrate primary cilia, a 9+0 structure with electron-dense materials in the center, a 9+2 structure with no dynein arms, and an axoneme with a disorganized structure at the distal end. Extensive description of cilia in the present study gives important insights into the evolution of the ciliary structure and provides a basis for analysis of ciliary functions in establishment of chordate body plan.
Developmental Biology 10/2009; 337(1):42-62. · 4.07 Impact Factor
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ABSTRACT: Ascidians, or sea squirts, are primitive chordates, and their tadpole larvae share a basic body plan with vertebrates, including a notochord and a dorsal tubular central nervous system (CNS). The CNS of the ascidian larva is formed through a process similar to vertebrate neurulation, while the ascidian CNS is remarkably simple, consisting of about 100 neurons. Recent identification of genes that are specifically expressed in a particular subtype of neurons has enabled us to reveal neuronal networks at single-cell resolution. Based on the information on neuron subtype-specific genes, different populations of neurons have been visualized by whole-mount in situ hybridization, immunohistochemical staining using specific antibodies, and fluorescence labeling of cell bodies and neurites by a fluorescence protein reporter driven by neuron-specific promoters. Neuronal populations that have been successfully visualized include glutamatergic, cholinergic, gamma-aminobutyric acid/glycinergic, and dopaminergic neurons, which have allowed us to propose functional regionalization of the CNS and a neural circuit for locomotion. Thus, the simple nervous system of the ascidian larva can serve as an attractive model system for studying the development, function, and evolution of the chordate nervous system.
Embryologia 05/2009; 51(3):207-20. · 2.21 Impact Factor
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ABSTRACT: In the course of embryogenesis multicellular structures and organs are assembled from constituent cells. One structural component common to many organs is the tube, which consists most simply of a luminal space surrounded by a single layer of epithelial cells. The notochord of ascidian Ciona forms a tube consisting of only 40 cells, and serves as a hydrostatic "skeleton" essential for swimming. While the early processes of convergent extension in ascidian notochord development have been extensively studied, the later phases of development, which include lumen formation, have not been well characterized. Here we used molecular markers and confocal imaging to describe tubulogenesis in the developing Ciona notochord. We found that during tubulogenesis each notochord cell established de novo apical domains, and underwent a mesenchymal-epithelial transition to become an unusual epithelial cell with two opposing apical domains. Concomitantly, extracellular luminal matrix was produced and deposited between notochord cells. Subsequently, each notochord cell simultaneously executed two types of crawling movements bi-directionally along the anterior/posterior axis on the inner surface of notochordal sheath. Lamellipodia-like protrusions resulted in cell lengthening along the anterior/posterior axis, while the retraction of trailing edges of the same cell led to the merging of the two apical domains. As a result, the notochord cells acquired endothelial-like shape and formed the wall of the central lumen. Inhibition of actin polymerization prevented the cell movement and tube formation. Ciona notochord tube formation utilized an assortment of common and fundamental cellular processes including cell shape change, apical membrane biogenesis, cell/cell adhesion remodeling, dynamic cell crawling, and lumen matrix secretion.
Developmental Biology 04/2009; 330(2):237-49. · 4.07 Impact Factor
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ABSTRACT: In most ascidians, metamorphosis of tadpole-like swimming larvae is accompanied by dynamic changes in their shape to form sessile adults. The mechanisms underlying ascidian metamorphosis have been debated for a long time. Although recent molecular studies have revealed the presence of various molecules involving in this process, the basic mechanism of the metamorphic events is still unclear. For example, it has not been solved whether all metamorphic events are organized by the same single pathway or by multiple, independent pathways. In the present study, we approached this question using the ascidian Ciona intestinalis. When the papillae and preoral lobes of the larvae were cut off, the papillae-cut larvae initiated certain trunk metamorphic events such as the formation of an ampulla, body axis rotation and adult organ growth without other metamorphic events. This observation indicates that metamorphic events can be divided into at least two groups, events initiated in the papillae-cut larva and events not initiated in this larva. In addition to this observation, we have isolated a novel mutant, tail regression failed (trf), which shows similar phenotypes to those of papillae-cut larvae. The phenotypes of trf mutants are basically different from those of swimming juvenile mutants (Sasakura, Y., Nakashima, K., Awazu, S., Matsuoka, T., Nakayama, A., Azuma, J., Satoh, N., 2005. Transposon-mediated insertional mutagenesis revealed the functions of animal cellulose synthase in the ascidian Ciona intestinalis. Proc. Natl. Acad. Sci. U. S. A. 102, 15134-15139.), which also show abnormal metamorphosis. These findings suggest a model by which ascidian metamorphic events can be classified into four groups initiated by different pathways.
Developmental Biology 01/2009; 326(2):357-67. · 4.07 Impact Factor
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ABSTRACT: The vertebrate-type opsin, Ci-opsin1, is localized in the outer segments of the photoreceptor cells of larvae of the ascidian Ciona intestinalis. The absorption spectrum of the photopigment reconstituted from Ci-opsin1 and 11-cis-retinal suggested that the photopigment is responsible for photic behavior of the larvae. The structure and function of Ci-opsin1-positive photoreceptor cells were examined by immunohistochemistry, confocal microscopy, electron microscopy, laser ablation, and behavioral analysis. Ciona larvae have three morphologically distinct groups of photoreceptor cells in the brain vesicle. Group I and group II photoreceptor cells are associated with the ocellus pigment cell on the right side of the brain vesicle. The outer segments of the group I photoreceptor cells are regularly arranged inside the small cavity encircled by the cup-shaped pigment cell. The outer segments of the group II photoreceptor cells are located outside the pigment cavity and exposed to the lumen of the brain vesicle. The outer segments of the group III photoreceptor cells are located near the otolith on the left ventral side of the brain vesicle. Thus, the brain vesicle of the ascidian larva has two ocelli: a 'conventional' pigmented ocellus containing the group I and group II photoreceptor cells and a novel nonpigmented ocellus solely consisting of the group III photoreceptor cells. Laser ablation experiments suggest that the pigmented ocellus is responsible for the photic swimming behavior. The nonpigmented ocellus might relate to later developmental or physiological events, such as metamorphosis, because Ci-opsin1 immunoreactivity appears in the late larval stage and becomes intense just before the onset of metamorphosis.
The Journal of Comparative Neurology 08/2008; 509(1):88-102. · 3.81 Impact Factor
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ABSTRACT: Glutamate is a major neurotransmitter in the excitatory synapses of both vertebrate and invertebrate nervous systems and is involved in many neural processes including photo-, mechano-, and chemosensations, neural development, motor control, learning, and memory. We identified and characterized the gene (Ci-VGLUT) encoding a member of the vesicular glutamate transporter subfamily, a specific marker of glutamatergic neurons, in the ascidian Ciona intestinalis. The Ci-VGLUT gene is expressed in the adhesive organ, the epidermal neurons, and the brain vesicle, but not in the visceral ganglion. The Ci-VGLUT promoter and an anti-Ci-VGLUT antibody were used to analyze the distribution and axonal connections of prospective glutamatergic neurons in the C. intestinalis larva. The green fluorescent protein (GFP) reporter driven by the 4.6-kb upstream region of Ci-VGLUT recapitulated the endogenous gene expression patterns and visualized both the cell bodies and neurites of glutamatergic neurons. Papillar neurons of the adhesive organs, almost all epidermal neurons, the otolith cell, and ocellus photoreceptor cells were shown to be glutamatergic. Each papillar neuron connects with a rostral epidermal neuron. Axons from rostral epidermal neurons, ocellus photoreceptor cells, and neurons underlying the otolith terminate in the posterior brain vesicle. Some caudal epidermal neurons also send long axons toward the brain vesicle. The posterior brain vesicle contains a group of Ci-VGLUT-positive neurons that send axons posteriorly to the visceral ganglion. Our results suggest that glutamatergic neurotransmission plays a major role in sensory systems and in the integration of the sensory inputs of the ascidian larva.
The Journal of Comparative Neurology 06/2008; 508(2):249-63. · 3.81 Impact Factor
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ABSTRACT: The larval nervous system of the ascidian Ciona intestinalis exhibits an abstract form of the vertebrate nervous system. The Ci-Galphai1 gene, which encodes a G-protein alpha subunit, is specifically expressed in distinct sets of neurons in C. intestinalis larvae, including papillar neurons of the adhesive organ, ocellus photoreceptor cells, and cholinergic and GABAergic neurons in the central nervous system (CNS). A GFP reporter gene driven by the 4.2-kb 5' flanking region of Ci-Galphai1 recapitulated the endogenous gene expression patterns. Comparative genomic analysis of the Galphai1 gene between C. intestinalis and Ciona savignyi identified an 87-bp highly conserved non-coding sequence located between -3176 and -3090 bp upstream of the gene. Deletion of this conserved upstream sequence resulted in the complete loss of reporter expression in the central nervous system, while reporter expression in the adhesive organ and mesenchyme cells remained unaffected. The conserved upstream sequence can activate gene expression from basal promoters in the brain vesicle, although it requires additional cis-regulatory sequences to fully activate the CNS-specific gene expression. These results suggest that different types of central neurons share a common transcriptional activation mechanism that is different from that of papillar neurons.
Embryologia 11/2007; 49(8):657-67. · 2.21 Impact Factor
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ABSTRACT: Although there have been several studies on the structure of the ocellus photoreceptors in ascidian tadpole larvae using electron microscopy, the overall structure of these photoreceptor cells, especially the projection sites of the axons, has not been revealed completely. The number of photoreceptor cells is also controversial. Here, the whole structure of the ocellus photoreceptors in the larvae of the ascidian Ciona intestinalis was revealed by using an anti-arrestin (anti-Ci-Arr) antibody. The cell bodies of 30 photoreceptor cells covered the right side of the ocellus pigment cell and their outer segments extended through the pigment cell into the pigment cup. The axons of the photoreceptor cells were bundled together ventro-posteriorly in a single tract extending towards the midline. The nerve terminals diverged antero-posteriorly at the midline of the posterior sensory vesicle (SV). The Ci-arr gene was expressed throughout the SV at the embryonic mid-tailbud stage and it became restricted to the neighborhood of the ocellus pigment when ocellus pigmentation occurred. At the same time, the Ci-Arr protein was first detected, suggesting that the photoreceptor cells began to differentiate. The development of photoreceptor cells after hatching was also investigated using the anti-Ci-Arr antibody. Three hours after hatching, the photoreceptor terminals began to ramify and then expanded. Previous behavioral analysis showed that the larvae did not respond to the step-down of light until 2 h after hatching and then the photoresponse became robust. Accordingly, our results suggest that growth of the photoreceptor terminal is critical for the larvae to become photoresponsive.
Journal of Neurobiology 01/2006; 65(3):241-50. · 3.05 Impact Factor
