Tools for Gene Editing in Marmosets SUMMARY The goal of this proposal is to create an efficient new set of tools and techniques for the generation of genetically modified marmosets suitable for use as models of brain physiology and function. Development of efficient methods of genetic manipulation in the species will require refinement of genome editing technologies, breeding technologies, ovarian stimulation and oocyte retrieval, embryo culture, and pre-implantation screening of embryos for the desired genetic alternations. A large colony of marmosets will be necessary, along with an infrastructure to refine technologies and an interdisciplinary team with expertise in marmoset care, assisted reproduction technologies, tissue-specific expression with Cre-drivers and CRISPR technologies, and behavior testing and neuropsychiatric analysis. The Specific Aims of this proposal are to: (1) Improve technology for in vitro genetic manipulation of marmosets and explore novel methods for marmoset gene editing; (2) Identify safe harbor loci and establish Cas9, Cre, and GCaMP marmoset lines using promoters for ubiquitous expression, selective expression in brain, or regional or cell-type specific expression; and (3) Generate marmoset models with genetic alterations relevant to the neurobiology of human brain diseases. These studies will provide tools for future gene editing experiments in marmosets, will establish an initial set of genetically modified tool lines for use in the field, and will provide initial proof-of-principle lines for marmoset models of genetic alterations potentially relevant to the neurobiology of human brain diseases.