Change in the developmental fate of the chick optic vesicle from the neural retina to the telencephalon.

The forebrain develops into the telencephalon, diencephalon, and optic vesicle (OV). The OV further develops into the optic cup, the inner and outer layers of which develop into the neural retina and retinal pigmented epithelium (RPE), respectively. We studied the change in fate of the OV by using embryonic transplantation and explant culture methods.

Regulation of neuronal and photoreceptor cell differentiation by Wnt signaling from iris-derived stem/progenitor cells of the chick in flat vs. Matrigel-embedding cultures.

Previously we developed a simple culture method of the iris tissues and reported novel properties of neural stem/progenitor-like cells in the iris tissues of the chick and pig. When the iris epithelium or connective tissue (stroma) was treated with dispase, embedded in Matrigel, and cultured, neuronal cells extended from the explants within 24 h of culture, and cells positively stained for photoreceptor cell markers were also observed within a few days of culturing. In ordinary flat tissue culture conditions, explants had the same differentiation properties to those in tissue environments.

Recent Developments in the Treatment of Ankle and Subtalar Instability.

It was nearly a centenary ago that severe ankle sprain was recognized as an injury of the ankle ligament(s). With the recent technological advances and tools in imaging and surgical procedures, the management of ankle sprains - including subtalar injuries - has drastically improved. The repair or reconstruction of ankle ligaments is getting more anatomical and less invasive than previously.

A novel culture method reveals unique neural stem/progenitors in mature porcine iris tissues that differentiate into neuronal and rod photoreceptor-like cells.

Iris neural stem/progenitor cells from mature porcine eyes were investigated using a new protocol for tissue culture, which consists of dispase treatment and Matrigel embedding. We used a number of culture conditions and found an intense differentiation of neuronal cells from both the iris pigmented epithelial (IPE) cells and the stroma tissue cells. Rod photoreceptor-like cells were also observed but mostly in a later stage of culture.

Upregulation of matrix metalloproteinase triggers transdifferentiation of retinal pigmented epithelial cells in Xenopus laevis: A Link between inflammatory response and regeneration.

In adult Xenopus eyes, when the whole retina is removed, retinal pigmented epithelial (RPE) cells become activated to be retinal stem cells and regenerate the whole retina. In the present study, using a tissue culture model, it was examined whether upregulation of matrix metalloproteinases (Mmps) triggers retinal regeneration. Soon after retinal removal, Xmmp9 and Xmmp18 were strongly upregulated in the tissues of the RPE and the choroid.

Localization of Neurensin1 in cerebellar Purkinje cells of the developing chick and its possible function in dendrite formation.

Neurensin1 (Nrsn1) gene, highly specific to neurons, has been considered to play a role in neurite growth during neuronal development and regeneration in mice. Intense expression of Nrsn1 was found particularly in projecting neurons like retinal ganglion cells and spinal motor neurons, suggesting that Neurensin1 is needed for active neurite growth. In the present study we cloned chick Nrsn1 gene and produced an antibody against cNrsn1 to examine Nrsn1 localization in the chick brain, since the chick is a suitable animal model for the study of developmental neurobiology.

Immediate differentiation of neuronal cells from stem/progenitor-like cells in the avian iris tissues.

A simple culture method that was recently developed in our laboratory was applied to the chick iris tissues to characterize neural stem/progenitor-like cells. Iris tissue is a non-neuronal tissue and does not contain any neuronal cells. In the present study we isolated iris tissues from chick embryos just prior to hatching.

Abnormal retinal development associated with FRMD7 mutations.

Idiopathic infantile nystagmus (IIN) is a genetically heterogeneous disorder, often associated with FRMD7 mutations. As the appearance of the retina is reported to be normal based on conventional fundus photography, IIN is postulated to arise from abnormal cortical development. To determine whether the afferent visual system is involved in FRMD7 mutations, we performed in situ hybridization studies in human embryonic and fetal stages (35 days post-ovulation to 9 weeks post-conception).

Retinal stem/progenitor cells in the ciliary marginal zone complete retinal regeneration: a study of retinal regeneration in a novel animal model.

Our research group has extensively studied retinal regeneration in adult Xenopus laevis. However, X. laevis does not represent a suitable model for multigenerational genetics and genomic approaches.

RPE specification in the chick is mediated by surface ectoderm-derived BMP and Wnt signalling.

The retinal pigment epithelium (RPE) is indispensable for vertebrate eye development and vision. In the classical model of optic vesicle patterning, the surface ectoderm produces fibroblast growth factors (FGFs) that specify the neural retina (NR) distally, whereas TGFβ family members released from the proximal mesenchyme are involved in RPE specification. However, we previously proposed that bone morphogenetic proteins (BMPs) released from the surface ectoderm are essential for RPE specification in chick.

Loss of cell-extracellular matrix interaction triggers retinal regeneration accompanied by Rax and Pax6 activation.

The whole retina regenerates from retinal pigmented epithelial (RPE) cells by transdifferentiation in the adult newt and Xenopus laevis when it is surgically removed. We produced a transgenic animal line, in which EGFP expression is under the control of Rax pomotor. Using F1 and F2 generations, we analyzed Rax-EGFP expression during retinal regeneration in a tissue culture model.

Transgenic Xenopus laevis with the ef1-α promoter as an experimental tool for amphibian retinal regeneration study.

Complete retinal regeneration occurs after the removal of the whole tissue in mature Xenopus laevis, as well as in the newt. Here, we produced F1 and F2 lines of transgenic X. laevis containing an EGFP gene under a translation elongation factor 1-α (ef1-α) promoter and investigated how the gene is reactivated in retinal pigmented epithelial (RPE) cells when the neural retina (NR) is removed.

The clinical and molecular genetic features of idiopathic infantile periodic alternating nystagmus.

Periodic alternating nystagmus consists of involuntary oscillations of the eyes with cyclical changes of nystagmus direction. It can occur during infancy (e.g.

Coordinated regulation of dorsal bone morphogenetic protein 4 and ventral Sonic hedgehog signaling specifies the dorso-ventral polarity in the optic vesicle and governs ocular morphogenesis through fibroblast growth factor 8 upregulation.

Dorsal and ventral specification in the early optic vesicle plays a crucial role in vertebrate ocular morphogenesis, and proper dorsal-ventral polarity in the optic vesicle ensures that distinct structures develop in separate domains within the eye primordium. The polarity is determined progressively during development by coordinated regulation of extraocular dorsal and ventral factors. In the present study, we cultured discrete portions of embryonic chick brains by preparing anterior cephalon, anterior dorsal cephalon and anterior ventral cephalon, and clearly demonstrate that bone morphogenetic protein 4 (BMP4) and Sonic hedgehog (Shh) constitute a dorsal-ventral signaling system together with fibroblast growth factor 8 (FGF8).

Generation of a second eye by embryonic transplantation of the antero-ventral hemicephalon.

Vertebrate ocular morphogenesis requires proper dorso-ventral polarity within the optic vesicle, and loss of dorso-ventral polarity results in failure of optic cup formation and domain specification, as shown by a reverse transplantation of the optic vesicle. We have shown previously that the ocular development depends not only on the signal within the antero-ventral optic vesicle but also on the extraocular signals. In the present study, using embryonic transplantation of a discrete portion of the embryonic chick brain, we demonstrate formation of a second eye from the antero-ventral hemicephalon when it was transplanted in the antero-dorsal hemicephalon of the host embryo.

Complete reconstruction of the retinal laminar structure from a cultured retinal pigment epithelium is triggered by altered tissue interaction and promoted by overlaid extracellular matrices.

The retina regenerates from retinal pigment epithelial (RPE) cells by transdifferentiation in the adult newt and Xenopus laevis when it is surgically removed. This was studied under a novel culture condition, and we succeeded, for the first time, in developing a complete retinal laminar structure from a single epithelial sheet of RPE. We cultured a Xenopus RPE monolayer sheet isolated from the choroid on a filter cup with gels overlaid and found that the retinal tissue structure differentiated with all retinal layers present.

Anteroventrally localized activity in the optic vesicle plays a crucial role in the optic development.

The vertebrate eye develops from the optic vesicle (OV), a laterally protrusive structure of the forebrain, by a coordinated interaction with surrounding tissues. The OV then invaginates to form an optic cup, and the lens placode develops to the lens vesicle at the same time. These aspects in the early stage characterize vertebrate eye formation and are controlled by appropriate dorsal-ventral coordination.

Differential enhancement of neural and photoreceptor cell differentiation of cultured pineal cells by FGF-1, IGF-1, and EGF.

There are several common features between the pineal organ and the lateral eye in their developmental and evolutionary aspects. The avian pineal is a photoendocrine organ that originates from the diencephalon roof and represents a transitional type between the photosensory organ of lower vertebrates and the endocrine gland of mammals. Previous cell culture studies have shown that embryonic avian pineal cells retain a wide spectrum of differentiative capacities, although little is known about the mechanisms involved in their fate determination.

Regulatory expression of Neurensin-1 in the spinal motor neurons after mouse sciatic nerve injury.

Axonal regeneration after crush injury of the sciatic nerve has been intensely studied for the elucidation of molecular and cellular mechanisms. Neurite extension factor1 (Nrsn1) is a unique membranous protein that has a microtubule-binding domain and is specifically expressed in neurons. Our studies have shown that Nrsn1 is localized particularly in actively extending neurites, thus playing a role in membrane transport to the growing distal ends of extending neurites.

Regeneration of the amphibian retina: role of tissue interaction and related signaling molecules on RPE transdifferentiation.

Regeneration of eye tissue is one of the classic subjects in developmental biology and it is now being vigorously studied to reveal the cellular and molecular mechanisms involved. Although many experimental animal models have been studied, there may be a common basic mechanism that governs retinal regeneration. This can also control ocular development, suggesting the existence of a common principle between the development and regeneration of eye tissues.

Neural retinal regeneration in the anuran amphibian Xenopus laevis post-metamorphosis: transdifferentiation of retinal pigmented epithelium regenerates the neural retina.

In urodele amphibians like the newt, complete retina and lens regeneration occurs throughout their lives. In contrast, anuran amphibians retain this capacity only in the larval stage and quickly lose it during metamorphosis. It is believed that they are unable to regenerate these tissues after metamorphosis.

Neurensin-1 expression in the mouse retina during postnatal development and in the cultured retinal neurons.

Neurensin-1/Neuro-p24 (previously named Neuro-p24) is a neuron-specific membrane protein that is localized particularly in neurites. Neurensin-1 is considered to play an essential role in neurite extension during nervous development, regeneration and plasticity. To understand what role Neurensin-1 plays in retinal differentiation, we examined Neurensin-1 distribution and gene expression pattern in the postnatally developing retina of the mouse, because the retina is an excellent model for nervous development.

Molecular characterization of a transport vesicle protein Neurensin-2, a homologue of Neurensin-1, expressed in neural cells.

We have isolated and characterized a novel cDNA encoding a small neuronal membrane protein showing high sequence homology to Neuro-p24/Neurensin-1, a protein containing a microtubule-associated domain at the carboxyl-terminus and exclusively localized to small vesicles of neurons. The newly identified Neurensin-2 constitutes two-membrane spanning domains but not the microtubule-binding domain, with a molecular mass of 28 kDa. Neurensin-2 mRNA is expressed only in brain, whereas the protein expressed in various neurons including those of the thalamus/hypothalamus and hippocampus, of postnatally developing mice.

Extraocular dorsal signal affects the developmental fate of the optic vesicle and patterns the optic neuroepithelium.

Dorsal-ventral (DV) specification in the early optic vesicle plays a crucial role in the proper development of the eye. To address the questions of how DV specification is determined and how it affects fate determination of the optic vesicle, isolated optic vesicles were cultured either in vitro or in ovo. The dorsal and ventral halves of the optic vesicle were fated to develop into retinal pigment epithelium (RPE) and neural retina, respectively, when they were separated from each other and cultured.