Biomedical subjects

Panagiotis A Tsonis

Publications and source records attributed to Panagiotis A Tsonis.

25 records · Page 2Linked to original sources

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

Regenerative biology: the emerging field of tissue repair and restoration.

Regenerative biology has now been recognized as a new field with certain aims and goals. One direction of this new field is to understand the basic mechanisms by which tissues can be repaired and restored. The other direction examines the possibility of using this basic knowledge to apply it to medicine with the goal to clinically repair damaged tissues. Regeneration of tissues can occur by the differentiation of stem cells (local or non-local) or by the transdifferentiation of local terminally differentiated cells. While the transdifferentiation aspects are old, during the past few years many data have accumulated regarding the existence of stem cells and their participation in tissue renewal. This review will present an overview of the potential of all vertebrate organs to regenerate and of the basic mechanisms involved.

Adrenal Glands↗

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↗