The tunicate Ciona : a model system for understanding the relationship between regeneration and aging

© 2014 The Author(s). This is an Open Access article. The definitive version was published in Invertebrate Reproduction & Development 59, Supple. 1 (2015): 17-22, doi:10.1080/07924259.2014.925515.The use of the tunicate Ciona intestinalis as a model system to study the relationship between regeneration and aging is reviewed. Ciona has powerful regeneration capacities, which fade with age. Some additional benefits are a relatively short life span, the ability to study regeneration in vitro, the close phylogenetic relationship between tunicates and vertebrates, and the host of molecular tools already established in this system. The neural complex (NC), the oral siphon (OS), and the oral siphon pigment organs (OPO) have high capacities for regeneration. However, these organs show an inverse relationship between rate of regeneration and age. The ability to regenerate a complete OS disappears in the oldest animals of a natural population, probably due to the inability to form a blastema at the wound site. Effects on blastema formation could also be involved in the reduction of NC regeneration capacity. The fidelity of OPO restoration is also compromised by excess differentiation of precursor cells in local siphon niches in the oldest animals. The Ciona model provides a pathway to understand the molecular basis of these phenomena.This work was supported by NIH [grant number R01AG037918]

Distal regeneration involves the age dependent activity of branchial sac stem cells in the ascidian Ciona intestinalis

© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Regeneration 2 (2015): 1-18, doi:10.1002/reg2.26.Tunicates have high capacities for regeneration but the underlying mechanisms and their relationship to life cycle progression are not well understood. Here we investigate the regeneration of distal structures in the ascidian tunicate Ciona intestinalis. Analysis of regenerative potential along the proximal−distal body axis indicated that distal organs, such as the siphons, their pigmented sensory organs, and the neural complex, could only be replaced from body fragments containing the branchial sac. Distal regeneration involves the formation of a blastema composed of cells that undergo cell proliferation prior to differentiation and cells that differentiate without cell proliferation. Both cell types originate in the branchial sac and appear in the blastema at different times after distal injury. Whereas the branchial sac stem cells are present in young animals, they are depleted in old animals that have lost their regeneration capacity. Thus Ciona adults contain a population of age-related stem cells located in the branchial sac that are a source of precursors for distal body regeneration.This research was supported by NIH grant R01AG037918

Ascidian gene-expression profiles

With the advent of gene-expression profiling, a large number of genes can now be investigated simultaneously during critical stages of development. This approach will be particularly informative in studies of ascidians, basal chordates whose genomes and embryology are uniquely suited for mapping developmental gene networks

Evolution and development in cave animals: from fish to crustaceans

Cave animals are excellent models to study the general principles of evolution as well as the mechanisms of adaptation to a novel environment: the perpetual darkness of caves. In this article, two of the major model systems used to study the evolution and development (evo–devo) of cave animals are described: the teleost fish Astyanax mexicanus and the isopod crustacean Asellus aquaticus. The ways in which these animals match the major attributes expected of an evo–devo cave animal model system are described. For both species, we enumerate the regressive and constructive troglomorphic traits that have evolved during their adaptation to cave life, the developmental and genetic basis of these traits, the possible evolutionary forces responsible for them, and potential new areas in which these model systems could be used for further exploration of the evolution of cave animals. Furthermore, we compare the two model cave animals to investigate the mechanisms of troglomorphic evolution. Finally, we propose a few other cave animal systems that would be suitable for development as additional models to obtain a more comprehensive understanding of the developmental and genetic mechanisms involved in troglomorphic evolution

Pleiotropic functions of embryonic sonic hedgehog expression link jaw and taste bud amplification with eye loss during cavefish evolution

This study addresses the role of sonic hedgehog (shh) in increasing oral-pharyngeal constructive traits (jaws and taste buds) at the expense of eyes in the blind cavefish Astyanax mexicanus. In cavefish embryos, eye primordia degenerate under the influence of hyperactive Shh signaling. In concert, cavefish show amplified jaw size and taste bud numbers as part of a change in feeding behavior. To determine whether pleiotropic effects of hyperactive Shh signaling link these regressive and constructive traits, shh expression was compared during late development of the surface-dwelling (surface fish) and cave-dwelling (cavefish) forms of Astyanax. After an initial expansion along the midline of early embryos, shh was elevated in the oral-pharyngeal region in cavefish and later was confined to taste buds. The results of shh inhibition and overexpression experiments indicate that Shh signaling has an important role in oral and taste bud development. Conditional overexpression of an injected shh transgene at specific times in development showed that taste bud amplification and eye degeneration are sensitive to shh overexpression during the same early developmental period, although taste buds are not formed until much later. Genetic crosses between cavefish and surface fish revealed an inverse relationship between eye size and jaw size/taste bud number, supporting a link between oral-pharyngeal constructive traits and eye degeneration. The results suggest that hyperactive Shh signaling increases oral and taste bud amplification in cavefish at the expense of eyes. Therefore, selection for constructive oral-pharyngeal traits may be responsible for eye loss during cavefish evolution via pleiotropic function of the Shh signaling pathway. © 2009 Elsevier Inc. All rights reserved

Astyanax surface and cave fish morphs

The small teleost fish Astyanax mexicanus has emerged as an outstanding model for studying many biological topics in the context of evolution. A major attribute is conspecific surface dwelling (surface fish) and blind cave dwelling (cavefish) morphs that can be raised in the laboratory and spawn large numbers of transparent and synchronously developing embryos. More than 30 cavefish populations have been discovered, mostly in northeastern Mexico, and some are thought to have evolved independently from surface fish ancestors, providing excellent models of parallel and convergent evolution. Cavefish have evolved eye and pigmentation regression, as well as modifications in brain morphology, behaviors, heart regenerative capacity, metabolic processes, and craniofacial organization. Thus, the Astyanax model provides researchers with natural “mutants” to study life in the challenging cave environment. The application of powerful genetic approaches based on hybridization between the two morphs and between the different cavefish populations are key advantages for deciphering the developmental and genetic mechanisms regulating trait evolution. QTL analysis has revealed the genetic architectures of gained and lost traits. In addition, some cavefish traits resemble human diseases, offering novel models for biomedical research. Astyanax research is supported by genome assemblies, transcriptomes, tissue and organ transplantation, gene manipulation and editing, and stable transgenesis, and benefits from a welcoming and interactive research community that conducts integrated community projects and sponsors the International Astyanax Meeting (AIM).https://doi.org/10.1186/s13227-020-00159-

MATHEMATICAL FORMULAS FOR CALCULATING NET RETURNS FROM PARTICIPATION IN GOVERNMENT PROGRAMS, CRP, AND CROP INSURANCE ALTERNATIVES

The purpose of this report is to provide a revised version of the publication, "Mathematical Formulas for Calculating Net Returns from Participation in Government Commodity Programs including Marketing Loans" (Williams and Barnaby, 1994). The change in design of the government commodity programs and development of several crop insurance alternatives has been significant since the previous paper was published. The formulas for calculating net returns incorporate provisions from the Farm Security and Rural Investment Act of 2002 and several crop insurance designs developed in the 1990s. Individuals conducting research or education programs will be able to use this revision for reference when estimating net returns for producers under current commodity program and crop insurance plan provisions.Agricultural Finance,