Precision Medicine, CRISPR, and Genome Engineering Moving from Association to Biology and Therapeutics

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challenges that have not been fully addressed include unpredictable editing

outcomes (NHEJ vs. HDR) and a high rate of mosaicism among the founder ani-

mals. To tackle these challenges, it is crucial to develop a better understanding of the

timing and mechanisms of CRISPR/Cas9 targeting and its role in the DNA repair

process  in one-cell embryos to maximize the chance of achieving the desired

genome editing products.

The generation of animal models is no longer the tedious and time-consuming

process that it was in the recent past. A mid-sized core facility like ours can generate

enough mutant alleles for one CRISPR project each week, in addition to other rou-

tine work on vector construction, transgenic animal production, embryo/sperm

cryopreservation, in vitro fertilization, and embryo transfer. For each CRISPR proj-

ect, the number of the mutant alleles we generate is usually more than what research-

ers actually need. This illustrates the power of CRISPR/Cas9 genome-engineering

technology to rapidly advance genetic studies. Given its remarkable flexibility,

adaptability, and accessibility, we believe that the application of CRISPR can be

further developed for many more uses, far beyond the capacity of our current knowl-

edge and imagination.

Acknowledgements We thank current and former staff members, Yinhuai Chen, Huirong Xie,
Alexandra Falcone, Susan Martin, Melissa Scott, Evan Barr-Beare, Calista Falcone, Kendall
Smith  and Kristen Martin for performing the services and generating the data for this article;
Melissa Scott for commenting on the manuscript. This work was supported by Cincinnati
Children’s Research Foundation.

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4 A Transgenic Core Facility’s Experience in Genome Editing Revolution