Marko Horb - US grants

Project Summary ? Core Component This component outlines the various resources available to the community at the National Xenopus Resource (NXR) and a detailed progress report of the previous five years. We outline the infrastructure of the facility, describing the two main rooms housing X. laevis and X. tropicalis as well as the new room that was renovated in 2017. We provide a summary of the maintenance, breeding and distribution of frogs to the community. In the second aim we summarize the various resources and services available to the community, including cryopreserved sperm and the custom transgenesis and mutant resources that serve to enhance research using Xenopus through facilitating the creation of new frog lines that is often an impediment in the community because of the inability of individual labs to breed lines in their own institution. In the third aim, we describe how the NXR enhances novel Xenopus research through its offering of advanced training workshops, hosting of PI meetings and its research facility service. All of these aspects are made possible by the various facilities available at the Marine Biological Laboratory, including teaching labs, imaging core and on-site housing.

? DESCRIPTION (provided by applicant): Project Summary This proposal supports a project to construct over 100 different Xenopus mutants in key genes related to human disease. The proposed studies will use CRISPR/Cas and TALEN gene editing to create precise models of human disease in the amphibian Xenopus. After a survey of the Xenopus community, there are over 150 different mutants requested to support biomedical research in Xenopus. The current studies are focused on developing Xenopus models of many different diseases for the entire Xenopus community, and each mutant will be developed in close coordination with individual researchers. There are three main aims to this proposal. First, mutations in key genes will be produced in either Xenopus tropicalis or Xenopus laevis using CRISPR/Cas or TALEN gene editing methods. Second, we propose to develop the use of oocyte host transfer for the generation of mutants using CRISPR/Cas and TALEN methods; this will increase the efficiency with which mutations are induced prior to first embryonic cell division and to allow for the creation of uniform heterozygous mutations by limiting Cas9 activity only in the oocyte. Third, we will optimize knock-in strategies with CRISPR/Cas and/or TALEN. All of these aims will help enhance the utilization of CRISPR/Cas and TALEN gene editing methods in the Xenopus model system.

Amphibians are outstanding models for vertebrate physiology and development. Among their many advantages are inexpensive housing, production of large clutches of eggs and embryos, embryonic development outside the mother, ease of experimental manipulation, and an extensive existing literature characterizing many aspects of their biology. However, modern genetic approaches in amphibians are extremely limited by their long breeding cycles and the difficulty of rearing and maintaining lines of mutant animals. The approach detailed in this project overcomes the limitations by proposing gene editing in amphibian cultured cell lines where genetic manipulations are much simpler. Cells with the desired genetic modification are then used to generate mutant animals. Thus, with no breeding, the researcher obtains specific desired mutant animals in a very short time. Unlike animals, cell lines with desired mutations can be frozen and stored indefinitely. This approach has the potential to revolutionize genetic manipulation in amphibians, making it fast, efficient, and powerful. The project is intimately tied to the mission of the National Xenopus Resource (NXR) located at the Marine Biological Laboratory (MBL) in Woods Hole, MA in assisting scientists to make use of amphibian models, to develop new technologies, and to disseminate these tools to the scientific community. The NXR also has an important function in educating students and teachers at all levels. The NXR carries out its mandates through participation in the many courses held at the MBL, by hosting hands-on workshops in genetic manipulation of amphibians, and through visits by scientists, students and educators.

Despite their many advantages for studies in fields such as development, regeneration and vertebrate physiology, amphibians lack practical methods for generating F0 (first generation) embryos with precisely defined, biallelic mutations. The long-term goal of the project is to make Xenopus and other amphibians vastly more powerful systems by simplifying the generation of precisely defined mutant animals. Another, overarching goal is to generalize this approach to enable the production of F0 mutants in a wide variety of vertebrate and invertebrate species, particularly in emerging models with little or no conventional genetics. The specific objectives of this project are to develop reliable methods for generating X. laevis, X. tropicalis, and axolotl cell lines with specific mutations, primarily using CRISPR-Cas9 technology. These cell lines can be cloned, fully characterized to define the specific genetic change, then stored frozen indefinitely. Nuclei from these cells will then be transferred to enucleated eggs and used to generate F0 mutant amphibian embryos. The assembled team combines expertise in amphibian cell culture and embryology and is particularly well-suited for carrying out this project and for rapid and efficient transmission of the technology to the scientific community.

Project Summary This supplemental request supports work to expand the National Xenopus Resource (NXR) through the renovation of approximately 850 sq ft of space to allow for live animals to be maintained in that space. The NXR is the national stock center for Xenopus laevis and Xenopus tropicalis animals and was founded in 2010. The need for additional space stems from the increase in genome editing technology that has revolutionized biomedical research, permitting the creation of mutant Xenopus. This new space will be used to maintain, breed and distribute mutant animals created by the Xenopus community, allowing access to these animals to all researchers. This is a critical renovation since this is the only Xenopus stock center. Newly funded research projects have proposed to create Xenopus models of human disease using genome editing, and these animals will be housed in this new space. Over the last few years there has been increased demand form the Xenopus community for custom mutant lines that are produced by the NXR and the current infrastructure is unable to support these additional mutant animals. This application requests funds to support the renovation of the space (HVAC, water, electrical, etc.) for the new Xenopus housing systems; the new equipment for housing he frogs has already been budgeted in other NIH-funded grants.

Project Summary/Abstract The focus of this conference is on the development and application of animal models to study human disease. Aquatic animals have many advantages and attributes that make them superior choices compared to mammalian models to investigate complex scientific questions. Aquatic animal models have played important roles in advancing our understanding of the origins of human disease and contributed to the study of drug targets and tests associated with the diagnosis, prevention and treatment of disease. There are many different aquatic animal models currently used in research, including zebrafish, Xenopus, aplysia, Xiphophorus, medaka as well as many marine species. The Aquatic Models of Human Disease Conference (AQMHD) is the only conference that brings together multiple aquatic models used to investigate the full range of human disease. These unique aquatic models represent a wide-range of innovative studies, methods and technologies that improve the conceptual understanding of the complexity of human disease. The Marine Biological Laboratory will host the 9th conference in this series in September 2018, bringing together researchers from the U.S. and around the world to engage in a program designed by recognized leaders in the field to provide state-of-the-art information on advances in the use of aquatic animals in biomedical research. This is a unique opportunity to host this aquatic model conference at the oldest marine laboratory in the United States. The dissemination of information, formal and informal engagement in discussion, and collaborative exchange of ideas will be achieved through a series of platform and poster sessions and workshops. New investigators, women, investigators with disabilities and under-represented minorities will be actively recruited to participate in this meeting through mechanisms such as travel awards. This year a strong effort is made to include more junior faculty representation. In addition, we have made efforts to increase participation and interactions at the poster sessions by organizing lightning talks prior to each poster session. Proceedings from past meetings have been published in special issues of a scientific journal and we will continue that mechanism for dissemination as well as attempt to publish a book providing a comprehensive review of the state of aquatic animal models and their use in human disease research. One outcome of these gatherings and this meeting in particular, is to provide new investigators with ideas, background, and mentoring required to improve the quality of grant applications submitted to multiple NIH institutes.

PROJECT SUMMARY The recent development of the CRISPR-Cas system has transformed many non-genetic models of cellular biology, yet the full application of its genome editing capabilities has been largely restricted to warm-blooded species and to genes which are easily amenable to current methods of CRISPR-Cas mediated gene disruption. Several species which live at lower temperatures, such as Xenopus and the marine models Loligo and Limulus, are ideal systems to model human disease, yet current methods of precise genome editing in these species are inadequate. Furthermore, due to their genomic architecture, many highly-conserved disease-causing genes are refractory to current methods of genome editing. We propose to expand the CRISPR-Cas mediated genome editing toolkit in the field of human disease modeling by driving innovation in two areas: 1) the development of a low-temperature CRISPR-Cas system capable of effecting targeted gene insertion in model species which thrive at lower temperatures, and 2) to develop a nascent system of targeted gene disruption by the application of CRISPR-Cas libraries.

Project Summary This grant supports a project to generate and characterize Xenopus mutants in key genes related to human disease, establish a new Xenopus Mutant Resource, develop new transgenic lines for genome editing and establish efficient site-specific integration. The long-term goals of the studies are to generate new models of human disease that will provide useful resources for the biomedical research community. The proposed studies will use CRISPR-Cas gene editing to create precise models of human disease in the amphibian Xenopus. The current studies are focused on developing Xenopus models of many different diseases for the entire Xenopus community, and each mutant will be developed in close coordination with individual researchers. There are four main aims to this proposal. First, we propose to collaborate with Xenopus researchers to characterize existing mutants (over 116) that were developed over the last four years. The mutants cover a wide range of topics that require varied expertise that can only be obtained through interactions with other researchers. Second, we propose to generate new mutants using CRISPR-Cas as requested by researchers. As the national stock center for Xenopus, we have the proven expertise to breed and maintain these mutants. Third, we will generate new transgenic lines that will be used for genome editing. These new lines will allow for more tissue-specific expression of Cas9. Fourth, we propose to develop homology directed repair for more efficient generation of site-specific integration of exogenous DNA. All of these aims will help enhance the utilization of CRISPR-Cas gene editing methods in the Xenopus model system.