PubMed Health⌕ Search

Biomedical subjects

Katia Del Rio-Tsonis

Publications and source records attributed to Katia Del Rio-Tsonis.

18 recordsLinked to original sources
PubMed2006

Identification of microRNAs and other small RNAs from the adult newt eye.

PURPOSE: MicroRNAs (miRNAs) are capable of controlling gene expression by targeting complimentary sequences in many mRNAs. Thus, a small number of miRNAs are capable of regulating expression of many different genes. miRNAs have been found in all animals from Drosophila to human and they are highly conserved. This work was undertaken in order to identify such RNAs in the newt eye. METHODS: Cloning of these RNAs was attempted after isolating and fractionating total RNA from the adult newt eye. A gel slice ranging from about 15 to 30 nucleotides in length was cut and the extracted RNA was cloned after several processes involving reverse transcription and linker addition. For expression analysis and verification during the process of lens regeneration we used as a probe mir-124a. RESULTS: Several microRNAs, piRNAs and other small RNAS were identified. Some of them have eye specific gene targets in other species, but for many a function in the eye remains to be attributed. Expression of miR-124a showed an interesting regulation in the lens regeneration-competent dorsal iris. CONCLUSIONS: The cloned miRNAs and other small RNAs are the first to be reported for this animal and might bear significance in regulating processes that are unique to the newt eye, i.e., regeneration of the lens and retina.

Animals↗
PubMed2006

The role of Pax-6 in lens regeneration.

Pax-6 is a master regulator of eye development and is expressed in the dorsal and ventral iris during newt lens regeneration. We show that expression of Pax-6 during newt lens regeneration coincides with cell proliferation. By knocking down expression of Pax-6 via treatment with morpholinos, we found that proliferation of iris pigment epithelial cells was dramatically reduced both in vitro and in vivo, and, as a result, lens regeneration was significantly retarded. However, induction of dedifferentiation in the dorsal iris was not inhibited. Pax-6 knockdown early in lens regeneration resulted in inhibition of crystallin expression and retardation of lens fiber induction. Once crystallin expression and differentiation of lens fibers has ensued, however, loss of function of Pax-6 did not affect crystallin expression and lens fiber maintenance, even though the effects on proliferation persisted. These results conclusively show that Pax-6 is associated with distinct early events during lens regeneration, namely control of cell proliferation and subsequent lens fiber differentiation.

Animals↗
PubMed2005

BMP inhibition-driven regulation of six-3 underlies induction of newt lens regeneration.

Lens regeneration in adult newts is a classic example of how cells can faithfully regenerate a complete organ through the process of transdifferentiation. After lens removal, the pigment epithelial cells of the dorsal, but not the ventral, iris dedifferentiate and then differentiate to form a new lens. Understanding how this process is regulated might provide clues about why lens regeneration does not occur in higher vertebrates. The genes six-3 and pax-6 are known to induce ectopic lenses during embryogenesis. Here we tested these genes, as well as members of the bone morphogenetic protein (BMP) pathway that regulate establishment of the dorsal-ventral axis in embryos, for their ability to induce lens regeneration. We show that the lens can be regenerated from the ventral iris when the BMP pathway is inhibited and when the iris is transfected with six-3 and treated with retinoic acid. In intact irises, six-3 is expressed at higher levels in the ventral than in the dorsal iris. During regeneration, however, only expression in the dorsal iris is significantly increased. Such an increase is seen in ventral irises only when they are induced to transdifferentiate by six-3 and retinoic acid or by BMP inhibitors. These data suggest that lens regeneration can be achieved in noncompetent adult tissues and that this regeneration occurs through a gene regulatory mechanism that is more complex than the dorsal expression of lens regeneration-specific genes.

Ambystoma↗
PubMed2005

CNS regeneration: a morphogen's tale.

Tissue regeneration will soon become an avenue for repair of damaged or diseased tissues as stem cell niches have been found in almost every organ of the vertebrate body including the CNS. In addition, different animals display an array of regenerative capabilities that are currently being researched to dissect the molecular mechanisms involved. This review concentrates on the different ways in which CNS tissues such as brain, spinal cord and retina can regenerate or display neurogenic potential and how these abilities are modulated by morphogens.

Animals↗
PubMed2004

Facile isolation and the characterization of human retinal stem cells.

This study identifies and characterizes retinal stem cells (RSCs) in early postnatal to seventh-decade human eyes. Different subregions of human eyes were dissociated and cultured by using a clonal sphere-forming assay. The stem cells were derived only from the pars plicata and pars plana of the retinal ciliary margin, at a frequency of approximately 1:500. To test for long-term self-renewal, both the sphere assay and monolayer passaging were used. By using the single sphere passaging assay, primary spheres were dissociated and replated, and individual spheres demonstrated 100% self-renewal, with single spheres giving rise to one or more new spheres in each subsequent passage. The clonal retinal spheres were plated under differentiation conditions to assay the differentiation potential of their progeny. The spheres were produced all of the different retinal cell types, demonstrating multipotentiality. Therefore, the human eye contains a small population of cells (approximately equal to 10,000 cells per eye) that have retinal stem-cell characteristics (proliferation, self-renewal, and multipotentiality). To test the in vivo potential of the stem cells and their progeny, we transplanted dissociated human retinal sphere cells, containing both stem cells and progenitors, into the eyes of postnatal day 1 NOD/SCID mice and embryonic chick eyes. The progeny of the RSCs were able to survive, migrate, integrate, and differentiate into the neural retina, especially as photoreceptors. Their facile isolation, integration, and differentiation suggest that human RSCs eventually may be valuable in treating human retinal diseases.

Adolescent↗
PubMed2004

A novel role of the hedgehog pathway in lens regeneration.

Lens regeneration in the adult newt is a classic example of replacing a lost organ by the process of transdifferentiation. After lens removal, the pigmented epithelial cells of the dorsal iris proliferate and dedifferentiate to form a lens vesicle, which subsequently differentiates to form a new lens. In searching for factors that control this remarkable process, we investigated the expression and role of hedgehog pathway members. These molecules are known to affect retina and pigment epithelium morphogenesis and have been recently shown to be involved in repair processes. Here we show that Shh, Ihh, ptc-1, and ptc-2 are expressed during lens regeneration. The expression of Shh and Ihh is quite unique since these genes have never been detected in lens. Interestingly, both Shh and Ihh are only expressed in the regenerating and developing lens, but not in the intact lens. Interfering with the hedgehog pathway results in considerable inhibition of the process of lens regeneration, including decreased cell proliferation as well as interference with lens fiber differentiation in the regenerating lens vesicle. Down-regulation of ptc-1 was also observed when inhibiting the pathway. These results provide the first evidence of a novel role for the hedgehog pathway in specific regulation of the regenerating lens.

Animals↗
PubMed2004

Lens regeneration in mice: implications in cataracts.

Lens regeneration in adult mice is possible when the lens capsule is left behind after lentectomy. The lens is regenerated by the remaining adherent lens epithelial cells, which differentiate to form lens fibres within days, showing normal morphology and bow regions. Epithelial to mesenchymal cell transformation is also seen during the early stages. The mouse, therefore, can become an indispensable animal model for cataract research, surgery and therapy.

Animals↗
PubMed2004

Lens and retina regeneration: transdifferentiation, stem cells and clinical applications.

In this review we present a synthesis on the potential of vertebrate eye tissue regeneration, such as lens and retina. Particular emphasis is given to two different strategies used for regeneration, transdifferentiation and stem cells. Similarities and differences between these two strategies are outlined and it is proposed that both strategies might follow common pathways. Furthermore, we elaborate on specific clinical applications as the outcome of regeneration-based research.

Animals↗
PubMed2004

The hedgehog pathway is a modulator of retina regeneration.

The embryonic chick has the ability to regenerate its retina after it has been completely removed. Here, we provide a detailed characterization of retina regeneration in the embryonic chick at the cellular level. Retina regeneration can occur in two distinct manners. The first is via transdifferentiation, which is induced by members of the Fibroblast growth factor (Fgf) family. The second type of retinal regeneration occurs from the anterior margin of the eye, near the ciliary body (CB) and ciliary marginal zone (CMZ). We show that regeneration from the CB/CMZ is the result of proliferating stem/progenitor cells. This type of regeneration is also stimulated by Fgf2, but we show that it can be activated by Sonic hedgehog (Shh) overexpression when no ectopic Fgf2 is present. Shh-stimulated activation of CB/CMZ regeneration is inhibited by the Fgf receptor (Fgfr) antagonist, PD173074. This indicates that Shh-induced regeneration acts through the Fgf signaling pathway. In addition, we show that the hedgehog (Hh) pathway plays a role in maintenance of the retina pigmented epithelium (RPE), as ectopic Shh expression inhibits transdifferentiation and Hh inhibition increases the transdifferentiation domain. Ectopic Shh expression in the regenerating retina also results in a decrease in the number of ganglion cells present and an increase in apoptosis mostly in the presumptive ganglion cell layer (GCL). However, Hh inhibition increases the number of ganglion cells but does not have an effect on cell death. Taken together, our results suggest that the hedgehog pathway is an important modulator of retina regeneration.

Animals↗
PubMed2004

A newt's eye view of lens regeneration.

In this paper we describe the basic process of lens regeneration in adult newt and we pinpoint several issues in order to obtain a comprehensive understanding of this ability, which is restricted to only a few salamanders. The process is characterized by dynamic changes in the organization of the extracellular matrix in the eye, re-entering of the cell cycle and dedifferentiation of the dorsal iris pigment epithelial cells. The ability of the dorsal iris to contribute to lens regeneration is discussed in light of iris-specific gene expression as well as in relation to factors present in the eye.

Animals↗
PubMed2004

Retina repair, stem cells and beyond.

In this review, we will explore several studies where stem cells from neural, non-neural and even embryonic cells have been used as potential sources to repair the damage retina. In addition, we will also discuss the possibility of inducing retina regeneration by transdifferentiation of cells present in existing eye tissues, such as, the Retinal Pigmented Epithelium (RPE), the Pigmented Ciliary Margin (PCM) and Müller glia cells.

Animals↗
PubMed2003

Three novel spermatogenesis-specific zinc finger genes.

We have cloned and characterized the expression, during spermatogenesis, of three novel zinc finger genes (Zfp94, Zfp95, Zfp96). Analysis of the deduced protein sequences reveals that all three molecules belong to the LeR family (leucine-rich zinc fingers) and that ZFP95 contains a domain homologous to the Krüppel-associated box. All three genes were found expressed at high levels in testis among other tissues, but testis-specific transcripts were observed for Zfp95 and Zfp96. Northern blot analyses of the testis-specific transcripts of Zfp95 and Zfp96 were performed using whole testis RNA as well as RNA isolated from enriched populations of specific spermatogenic cell types. The testis-specific transcript of Zfp95 showed the highest expression in pachytene spermatocytes, while that of Zfp96 was highly expressed in pachytene spermatocytes, in round spermatids and residual bodies. Northern blot analysis of RNA from the testis of mice carrying the atrichosis mutation further validated these expression patterns. In particular, the testis-specific transcripts of Zfp95 and Zfp96 were greatly reduced in heterozygous, and completely absent in homozygous testis RNA from atrichosis mutant mice, further defining the germ cell specificity of these transcripts.

Amino Acid Sequence↗
PubMed2003

Expression of complement 3 and complement 5 in newt limb and lens regeneration.

Some urodele amphibians possess the capacity to regenerate their body parts, including the limbs and the lens of the eye. The molecular pathway(s) involved in urodele regeneration are largely unknown. We have previously suggested that complement may participate in limb regeneration in axolotls. To further define its role in the regenerative process, we have examined the pattern of distribution and spatiotemporal expression of two key components, C3 and C5, during limb and lens regeneration in the newt Notophthalmus viridescens. First, we have cloned newt cDNAs encoding C3 and C5 and have generated Abs specifically recognizing these molecules. Using these newt-specific probes, we have found by in situ hybridization and immunohistochemical analysis that these molecules are expressed during both limb and lens regeneration, but not in the normal limb and lens. The C3 and C5 proteins were expressed in a complementary fashion during limb regeneration, with C3 being expressed mainly in the blastema and C5 exclusively in the wound epithelium. Similarly, during the process of lens regeneration, C3 was detected in the iris and cornea, while C5 was present in the regenerating lens vesicle as well as the cornea. The distinct expression profile of complement proteins in regenerative tissues of the urodele lens and limb supports a nonimmunologic function of complement in tissue regeneration and constitutes the first systematic effort to dissect its involvement in regenerative processes of lower vertebrate species.

Amino Acid Sequence↗
PubMed2003

Unique expression patterns of the retinoblastoma (Rb) gene in intact and lens regeneration-undergoing newt eyes.

Based on the role of retinoblastoma (Rb) in lens development and in the cell cycle reentry of muscle cells during limb regeneration, we have analyzed expression or Rb patterns in intact and lens regeneration-undergoing newt eyes. We find that in intact newt eye Rb is expressed in the retina as a gradient with higher levels in the photoreceptor layer and virtually no expression in the ganglion layer. In addition, a second gradient was detected within the photoreceptor layer with expression diminishing at the dorsal and ventral regions. In the intact lens, Rb is expressed in the lens epithelium and in the differentiating lens fibers at the bow region. During lens regeneration, Rb is expressed very strongly in the differentiating lens fibers, but not in the lens epithelium. Using an antibody specific to the hyperphosphorylated form of Rb, we detected the inactive protein only in the pigment epithelial cells of the iris. These distinct patterns might be related to the regenerative potential of the lens in the newt.

Animals↗
PubMed2003

Eye regeneration at the molecular age.

Eye tissues such as the lens and the retina possess remarkable regenerative abilities. In amphibians, a complete lens can be regenerated after lentectomy. The process is a classic example of transdifferentiation of one cell type to another. Likewise, retina can be regenerated, but the strategy used to replace the damaged retina differs, depending on the animal system and the age of the animal. Retina can be regenerated by transdifferentiation or by the use of stem cells. In this review, we present a synthesis on the regenerative capacity of eye tissues in different animals with emphasis on the strategy and the molecules involved. In addition, we stress the place of this field at the molecular age and the importance of the recent technologic advances.

Amphibians↗
PubMed2002

Expression and role of retinoic acid receptor alpha in lens regeneration.

The role of retinoids in eye development has been well studied. Retinoids and their receptors regulate gene expression and morphogenesis of the eye. In this study, a highly specific antagonist of retinoic acid receptor (RAR)-alpha was used in an attempt to study its function in lens regeneration. It was found that this antagonist inhibited lens regeneration and lens fiber differentiation. It was also shown that RAR-alpha is expressed in the lens during the process of regeneration. These results indicate that different RAR might have unique as well as redundant effects and patterns of expression in the regenerating lens.

Animals↗
PubMedDate not supplied

Effects of a CDK inhibitor on lens regeneration.

Lens regeneration in adult newts is always initiated from the dorsal iris by transdifferentiation of the pigment epithelial cells. One of the most important early events should be the ability of pigment epithelial cells to dedifferentiate and re-enter the cell cycle. As a first step in an attempt to study this event, we have decided to examine the effects of a cyclin-dependent kinase-2 inhibitor on lens regeneration. At the appropriate concentration, this inhibitor completely abolished the ability of pigment epithelial cells to form a new lens, but it did not stop them from dedifferentiating and forming a small lens vesicle. The effects of this inhibitor seem to be mediated by its opposite effects on cell proliferation and apoptosis. The inhibitor significantly reduced cell proliferation and enhanced apoptosis of pigment epithelial cells both in vitro and in vivo and of the regenerating lens in vivo.

Animals↗