Galliot Mechanisms of Regeneration

1. Auflage 2014
ISBN: 978-0-12-394410-8
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 108, 368 Seiten

Reihe: Current Topics in Developmental Biology

This new volume of Current Topics in Developmental Biology covers the area of mechanisms in regeneration. With an international board of authors, it provides a comprehensive set of reviews covering such topics as control of growth during regeneration, skeletal muscle degeneration and regeneration in mammals and flies, and suppression of regeneration in mammals. - Covers the area of mechanisms in regeneration - International board of authors - Provides a comprehensive set of reviews

Autoren/Hrsg.

Galliot, Brigitte

Leseproben

Preface
Brigitte Galliot The initial concept of this special issue was to invite a duo of experts for each chapter to discuss specific aspects of the mechanisms underlying regenerative processes. In some cases, this invitation came at the right time and two colleagues mutually agreed to join their efforts and deliver their views on a particular topic, within this largely multidisciplinary field that regeneration covers. In other cases, this dialectic pairing could not materialize and close collaborators joined to help write some chapters. In all cases, however, I would like to express my gratitude to every contributor of this special issue. Indeed, they all went far beyond their favorite model to discuss some of the most recent findings and strategies in their field, with a transversal view. As a result, this special issue offers both novel concepts and stimulating ideas on the various mechanisms at work during regeneration. In Chapter 1, Lin Xu and Hai Huang (Shanghai, China) provide an overview of the genetic and epigenetic control of the different regenerative processes in plants, not only in Arabidopsis thaliana but also in rice and moss. With clear words and excellent illustrations, the authors have made three regenerative contexts where regeneration operates in plants, that is, tissue repair, de novo organogenesis, and somatic embryogenesis, accessible to any biologists. Each of these processes corresponds to a cell fate transition, from cells that retain partial pluripotency when the root tip repairs, through the formation of an intermediate blastema-like structure named callus during de novo organogenesis, or through typical dedifferentiation of somatic cells during embryogenesis. Cell fate transition arises from a complex network of interactions involving chromatin, transcription factors, and hormones. In the case of somatic embryogenesis, these processes start to be well known and show some similarity with the mechanisms involved in the dedifferentiation of induced pluripotent stem cells from differentiated animal cells. In Chapter 2, Ying Hua Su and Xian Sheng Zhang (Shandong, China) continue along the same line with a specific focus on how hormones that behave as morphogens in plants control de novo organogenesis and somatic embryogenesis in Arabidopsis. The authors review recent advances on three important aspects, the biosynthetic regulation of hormonal functions, the cross talk between the auxin and cytokinin hormone signaling pathways, and the interactions between developmental and environmental cues. The authors of these two chapters leave us with a series of questions: What kinds of wound signals are released in the various contexts of plant regeneration? Which are the target genes of the plant hormones? How is the action of transcription and epigenetic factors coordinated? Which cells undergo callus initiation in natural conditions? The potential role of chromatin modifications in tissue repair and during animal regeneration remains obscure. In Chapter 3, Sofia Robb and Alejandro Sanchez Alvardo (Kansas City, USA) discuss recent findings concerning the role of histone modifications in the planarian flatworm Schmidtea mediterranea, which can regenerate any missing part due to its abundant and dynamic population of adult stem cells (ASCs) referred to as neoblasts. After an inventory of the histones and histone-modifying enzymes present in S. mediterranea, the authors show that a number of these enzymes are distributed in a way reminiscent of either stem cells or nerve cells. Functional studies involving one such histone deacetylase reveal that the regulation of the level of histone acetylation is essential to maintain the stem cell function of neoblasts, that is, self-renewal and differentiation of cell progeny. Therefore, planarians may provide a promising model for deciphering the epigenetic mechanisms that either underlie or accompany the regenerative potential in animals. In Chapter 4, Gongping Sun and Kenneth Irvine (Piscataway, USA) discuss the control of growth, both at the initiation and the termination phases of regeneration. Drosophila offers a versatile model to address this central question in regeneration, as wound healing can be tested not only in the embryo in the absence of any regeneration but also in the larvae either at the cuticle level or in the imaginal discs, where tissue ablation triggers regeneration. Finally, it can also be assessed in the adult cuticle or intestine, which displays an efficient tissue repair response. In each of these biological contexts, like in mammals regenerating their liver, the JNK pathway plays a central role in the injury response triggering the activation of various downstream signaling pathways, which may vary between organs. Recent quantitative genetic analyses performed in Drosophila show that injured tissues are more sensitive to a decrease in key signaling components as JAK or Yki, when compared to developing tissues or organs. Consequently, if the signaling pathways involved in the development and the regeneration of a given structure are the same, their interplay and their signaling strengths may importantly differ. This novel concept will surely generate further experiments in the future. In Chapter 5, Sophie Vriz (Paris, France), Silke Reiter, and Brigitte Galliot (Geneva, Switzerland) consider cell death as a possible motor for regeneration. After describing the various animal contexts where cell death positively influences regeneration, these authors discuss recent studies in Drosophila, zebrafish, and Hydra, all pointing to the production of ROS upon injury and its potential to activate the cell death program through the JNK and/or MAPK pathways. Cell death, however, does not always occur at the time and in the area of injury and may also be observed in more distant tissues with some delay. An important issue is to understand the different roles of these dying cells. The signaling molecules released by apoptotic cells are diverse and can instruct survivor cells. Dying cells can also provide a strong sentiment de vide (feeling of emptiness) to the neighboring tissues, which can rapidly develop a compensatory response involving enigmatic signaling components. Injury-induced cell death might thus be quite versatile, activating and/or deactivating a variety of mechanisms to trigger a regenerative program. In Chapter 6, Won-Jae Lee (Seoul, South Korea) and Masayuki Miura (Tokyo, Japan) discuss the impact of systemic wound response (SWR), a phenomenon they recently discovered whereby a local wound in the Drosophila adult skin (integument) can trigger long-distance responses. So far, these responses were identified in two distinct locations in the adult fly, in neuronal and intestinal cells by the Lee and Miura laboratories, respectively. Interestingly, both SWRs involve ROS signaling and are required for the survival of the adult animal. Consequently, we may no longer consider wound healing as a local process only, but also realize that injuries produce toxic systemic substances that engage reactions within the whole organism. What is the nature of these systemic factors? Which types of signaling do they elicit in each organ? Understanding how such toxic systemic factors circulating after a local damage affect the entire organism will help characterize the parameters that positively or negatively modulate the adult regenerative potential. The evolution of regenerative processes is poorly understood. In Chapter 7, Vladimir Mashanov, Olga Zueva and José García-Arrarás (San Juan, Puerto Rico) provide a comparative analysis of intestine regeneration across eumetazoans. Indeed, while the gut is the target of repeated environmental stresses, it nevertheless maintains day after day its essential capacity to absorb nutrients. Adult mammals and Drosophila efficiently repair their intestine epithelium due to a large stock of active stem cells. In addition, progenitors and some differentiated cells can revert to a stem cell stage in mammals. While these organisms are capable of repairing their gut, they are unable to regenerate any portion of it. Why? The authors use the sea cucumber Holothuria glaberrima, which spontaneously regenerates its whole gut after evisceration, to address this question. H. glaberrima regenerates its gut by recruiting both resident enterocytes coming from the luminal epithelium left in the stumps, and external cells evaginating from the surrounding connective tissue, thus providing new enterocytes after transdifferentiation. This dual contribution of resident and external cells is not restricted to echinoderms and is also observed in insects and vertebrates. Therefore, two distinct strategies, different from tissue self-renewal, and each relying on differentiated and/or stem cells, likely emerged in the course of animal evolution. Future studies on the interactions between the gut epithelium and the connective tissue should help understand the underlying mechanisms. They may also contribute to the development of tissue bioengineering in humans. Aging processes are an important factor that downregulates the strength of regeneration in mammals. In Chapter 8, Konstantinos Sousounis, Joelle Baddour, and Panagiotis Tsonis (Dayton, USA) synthesize the results of studies assessing the impact of aging in five distinct types of adult mammalian stem cells (endothelial, hematopoietic, skeletal muscle, neural, mesenchymal). They also discuss the age-dependent changes of the regenerative potential of those organs capable of...