Editorial
Special Issue: Organogenesis
Organogenesis: variations on a theme Rhiannon Macrae In the most basic sense, an organ represents the coordination of similar cells to accomplish a specific function. Ranging in complexity from the simple tube-shaped heart of Ciona to the uncharted intricacies of the human brain, organs display immense variety in their size, shape, and function. They share, however, a common origin, arising through a process of tightly regulated cell division and differentiation steps from a multipotent progenitor. In this Special Issue of Trends in Genetics, together with a Special Issue in our sister journal Current Opinion in Genetics & Development, we explore different facets of organogenesis, highlighting that the developmental pathways of all organs, from flowers to faces, are variations on a theme. Mina Gouti, Vicki Metzis, and James Briscoe review the signaling pathways and downstream transcriptional networks that regulate spinal cord patterning, highlighting recent evidence suggesting that the spinal cord and anterior regions of the central nervous system (CNS) do not share a common origin. They discuss how the spinal cord is generated through the integration of extrinsic signals and spatiotemporal information, as well as how improved imaging methods combined with single cell transcriptomic analyses will shape our understanding of CNS formation. Luis Arnes and Lori Sussel continue the theme of integrating extrinsic signals, reviewing the mechanics of gene regulation involved in pancreas formation. They focus their discussion on the transduction of extrinsic signals involving histone modifications and long non-coding RNAs (lncRNAs), and argue that this epigenetic layer of regulation may offer a new therapeutic avenue for treating diabetes. Plants are perhaps the masters of organogenesis, continuing to grow new organs throughout their lives in response to a variety of environmental stimuli. In a review focused on leaf development, Aaron Sluis and Sarah Hake explore how plants balance the maintenance of postembryonic stem cell niches with continual differentiation by integrating multiple external cues, including light, temperature, and pathogenic factors. Sluis and Hake also discuss morphogenesis and describe how plants use similar systems to derive a huge range of structures. Terry Orr-Weaver also tackles the question of mechanics and morphogenesis in organ development in her discussion
of the role of ploidy in organogenesis. Ploidy offers cells a way to increase their size, a crucial component of organ formation. She covers examples of this unusual phenomenon in both plants and animals, and reviews the involvement of ploidy in wound healing and regeneration. Mathias Wernet, Michael Perry, and Claude Desplan consider organogenesis from an evolutionary perspective, reviewing recent work on rhodopsins in Drosophila melanogaster and other insects aimed at understanding the molecular developmental program of the eye. Insects have adapted their vision for all types of environments, but emerging evidence suggests that the underlying molecular mechanisms of eye development share a common core across this diverse group of species. Another evolutionary aspect of organogenesis is the increasing complexity of organs. Phillip Grote and Bernhard Herrmann argue in their review that lncRNAs, which are more prevalent in higher eukaryotes, can help to explain the correlated increase in organ complexity observed in these species. By expanding the regulatory toolbox, lncRNAs may allow greater fine-tuning of development, and hence more intricate developmental processes. Finally, two pieces focus on the regeneration of organs. Daniel Wehner and Gilbert Weidinger review the role of Wnt/b-catenin signaling and other pathways in the regeneration of the zebrafish fin. They critically evaluate if regeneration is equivalent to re-development at a molecular level, and suggest future experiments with emerging technology that may be able to more fully assess the mechanisms of regeneration. Finally, Helmuth Gehart and Hans Clevers provide an outlook on the prospects for repairing organs, using the liver and intestine as models. Although this is still far from the clinic, we now have sufficient knowledge to develop cell culture systems that may aid in transplants. We thank all the authors and reviewers for their contributions to this issue, and we thank you for reading it. We hope that you will continue your reading on organogenesis with the exciting articles in the current issue of Current Opinion in Genetics & Development. Your comments and ideas are always welcome; you can contact us with feedback or questions at [email protected].
Corresponding author: Macrae, R. ([email protected]). 0168-9525/ ß 2015 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tig.2015.04.003
Trends in Genetics, June 2015, Vol. 31, No. 6
281
Special Issue: Organogenesis
Organogenesis: variations on a theme Rhiannon Macrae In the most basic sense, an organ represents the coordination of similar cells to accomplish a specific function. Ranging in complexity from the simple tube-shaped heart of Ciona to the uncharted intricacies of the human brain, organs display immense variety in their size, shape, and function. They share, however, a common origin, arising through a process of tightly regulated cell division and differentiation steps from a multipotent progenitor. In this Special Issue of Trends in Genetics, together with a Special Issue in our sister journal Current Opinion in Genetics & Development, we explore different facets of organogenesis, highlighting that the developmental pathways of all organs, from flowers to faces, are variations on a theme. Mina Gouti, Vicki Metzis, and James Briscoe review the signaling pathways and downstream transcriptional networks that regulate spinal cord patterning, highlighting recent evidence suggesting that the spinal cord and anterior regions of the central nervous system (CNS) do not share a common origin. They discuss how the spinal cord is generated through the integration of extrinsic signals and spatiotemporal information, as well as how improved imaging methods combined with single cell transcriptomic analyses will shape our understanding of CNS formation. Luis Arnes and Lori Sussel continue the theme of integrating extrinsic signals, reviewing the mechanics of gene regulation involved in pancreas formation. They focus their discussion on the transduction of extrinsic signals involving histone modifications and long non-coding RNAs (lncRNAs), and argue that this epigenetic layer of regulation may offer a new therapeutic avenue for treating diabetes. Plants are perhaps the masters of organogenesis, continuing to grow new organs throughout their lives in response to a variety of environmental stimuli. In a review focused on leaf development, Aaron Sluis and Sarah Hake explore how plants balance the maintenance of postembryonic stem cell niches with continual differentiation by integrating multiple external cues, including light, temperature, and pathogenic factors. Sluis and Hake also discuss morphogenesis and describe how plants use similar systems to derive a huge range of structures. Terry Orr-Weaver also tackles the question of mechanics and morphogenesis in organ development in her discussion
of the role of ploidy in organogenesis. Ploidy offers cells a way to increase their size, a crucial component of organ formation. She covers examples of this unusual phenomenon in both plants and animals, and reviews the involvement of ploidy in wound healing and regeneration. Mathias Wernet, Michael Perry, and Claude Desplan consider organogenesis from an evolutionary perspective, reviewing recent work on rhodopsins in Drosophila melanogaster and other insects aimed at understanding the molecular developmental program of the eye. Insects have adapted their vision for all types of environments, but emerging evidence suggests that the underlying molecular mechanisms of eye development share a common core across this diverse group of species. Another evolutionary aspect of organogenesis is the increasing complexity of organs. Phillip Grote and Bernhard Herrmann argue in their review that lncRNAs, which are more prevalent in higher eukaryotes, can help to explain the correlated increase in organ complexity observed in these species. By expanding the regulatory toolbox, lncRNAs may allow greater fine-tuning of development, and hence more intricate developmental processes. Finally, two pieces focus on the regeneration of organs. Daniel Wehner and Gilbert Weidinger review the role of Wnt/b-catenin signaling and other pathways in the regeneration of the zebrafish fin. They critically evaluate if regeneration is equivalent to re-development at a molecular level, and suggest future experiments with emerging technology that may be able to more fully assess the mechanisms of regeneration. Finally, Helmuth Gehart and Hans Clevers provide an outlook on the prospects for repairing organs, using the liver and intestine as models. Although this is still far from the clinic, we now have sufficient knowledge to develop cell culture systems that may aid in transplants. We thank all the authors and reviewers for their contributions to this issue, and we thank you for reading it. We hope that you will continue your reading on organogenesis with the exciting articles in the current issue of Current Opinion in Genetics & Development. Your comments and ideas are always welcome; you can contact us with feedback or questions at [email protected].
Corresponding author: Macrae, R. ([email protected]). 0168-9525/ ß 2015 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tig.2015.04.003
Trends in Genetics, June 2015, Vol. 31, No. 6
281
