Research Models
|
Regina Kelder
Customized 3Rs Solutions for Genetically Engineered Mouse Models
From IVF to digital tools, technology is transforming the management of genetically engineered mouse models and reducing the use of animals in the process.
In 1974, MIT scientists Rudolph Jaenisch and Beatrice Mintz infected mouse embryos with a retrovirus to show that the viral DNA could integrate with the germline of the mouse, ushering in the era of transgenic mice that are ubiquitous in research today. Transgenic models have been used to study a variety of human diseases, from cancer and cystic fibrosis to rheumatoid arthritis and Alzheimer’s and they are a vital tool in drug development. Many drug studies, particularly in disease modeling and target validation, use genetically modified mice.
Over time, advances large and small have streamlined the creation of these precious models. Gene editing tools like CRISPR Cas/9 have quickened the time it takes to create such models, while sperm and embryo cryopreservation and in vitro fertilization have become pivotal in the management of Genetically Engineered Model (GEM) lines. As a global leader in the field of in vivo-based research, we are acutely aware of the need to demonstrate responsibly how we manage GEM colonies using a solid 3Rs approach and solid science. The adoption and refinement of advanced embryology and transgenic technologies, coupled with key digital tools, have led to dramatic improvement of our 3Rs performance and demonstrate that the technologies sustaining the improvement of the 3Rs also strongly participate in project success & reduction of delays, staff workload, and internal costs.
Streamline Budget and Research Programs for Your Genetically Engineered Models with a Trusted Partner
Uncover how our innovative IVF technology and rapid quarantine services save you significant time, while tailored housing, breeding, and cryopreservation give you varied cost-effective options to advance studies while supporting 3Rs animal reduction. Watch the Webinar Series
Applying the 3Rs to Genetically Engineered Mouse Models
To get a closer look at managing GEM colonies under the lens of 3Rs, Eureka connected with one of Charles River’s resident experts, Jean Cozzi, PhD, Innovation Manager of Genetically Engineered Models and Services (GEMS). Here are five significant advances cited by Dr. Cozzi that are propelling the field forward.
Accelerated Mouse Backcrossing
An essential process in genetics used to transfer a specific mutation or genetic trait from one genetic background to another is backcrossing. This is done to introduce a specific gene or trait from one mouse (the "donor" mouse) into the genetic background of the other mouse (the "recurrent" or "elite" mouse). The goal is to create offspring with a desirable trait from the donor mouse while retaining the desirable traits of the recurrent mouse. Backcrossing allows researchers to study the effects of different genes in different genetic contexts, enhancing the reproducibility and robustness of experimental outcomes.
Typically, backcrossing was done by taking different numbers of single-nucleotide polymorphisms (SNPs)—regions of the mouse genome in which two strains differ by a single base pair—and testing them in one microarray. However, using SNPs to accelerate backcrossing still takes too long and still requires around 226 animals, which leads to extended timelines and a drain on resources. But a novel method we introduced in December 2024 to accelerate backcrossing in mice offers a better way forward. By integrating in vitro fertilization and SNP analysis, we have been able to significantly shorten the backcrossing process from 65 weeks to 50 weeks, resulting in a 40% reduction in the number of animals used (from 226 to 137 animals) and a decrease in cage occupancy.
This Marker-Assisted Accelerated Backcrossing (MAX-BAX®) 2.0 combines IVF and the miniMUGA array that is designed SNPs from 241 classical inbred lines. Aside from the many cost benefits for customers, it is a stellar 3Rs tool. Since we have launched the new service >90% of customers are using MAX-BAX 2.0; only technical and scientific constraints may not allow some to use it from time to time.
Assisted Reproduction Technologies
In the field of genetically engineered mouse models, assisted reproduction technologies (ART) have been transformative, and not just for accelerated mouse backcrossing, which I discussed above. In fact, ART is the engine driving much of innovation in how we create, manage, and track GEMMs today and how we are able to meet our 3Rs goals.
Over the last 10 years, key techniques in mouse-assisted reproductive technologies (ART), such as sperm & embryo cryopreservation or in vitro fertilization (IVF), have become pivotal in the management of genetically engineered mouse lines. They have played a role in the production of live animals, protecting animals from pathogens, preserving genetic resources, and generating new strains of genetically modified animals. Using IVF requires 4,000 fewer female mice per year and reduces the number of cages needed by about 1,000. There are also workload and cost reductions using IVF.
Electroporation: It’s Electric
Delivering proteins, mRNA, or DNA to fertilized eggs is key to generating transgenic animals. Transgenic efficiency can rely heavily on the methodology applied to deliver the molecules. For small molecules, electroporation—using a pulse of electricity that opens the pores in the cell membranes—proves to be far superior to standard microinjection. The procedure is also a good 3Rs approach because it allows the reduction in the number of embryos used, and consequently that of the oocyte’s donor females. Using electroporation to deliver CRISPR/Cas9 reagents leads to higher survival rates (+30%) of mouse embryos and a higher ratio (+20%) of transgenic pups. This translates into 50% fewer embryos needed, a 3Rs plus.
Genotyping
For generations, genetically modified mice were largely genotyped using an invasive ear or tail biopsy. But with the development of easier and faster methodologies to generate genetically altered animals, convenient and humane methods to genotype these animals are increasingly important to research and to meet 3Rs objectives. Some already established non-invasive genotyping methods use oral swabs, hair, fecal pellets, anal swabs, and tears. Our lab previously established the value of oral swab genotyping in rabbits. Recently, we adapted the sampling method for mice.
Studies using oral swabs found that genotyping results were similar to those from biopsies. Moreover, samples can be stored and shipped in varying conditions. Oral swabs are suitable for every kind of PCR and routine genotyping. The age of animals is also an important factor; it is optimal to take swabs from animals older than 16 days – the same age as an ear biopsy. Animals that are identified with ear tags or tattoos are also good candidates, if a biopsy is not possible.
Digitalization
To maintain the integrity of research strains, prevent disease outbreaks, and ensure the ethical care and welfare of the animals, lab animal colony management is essential. Every detail must be meticulously recorded, and every animal must be assigned a number or ID. A single misplaced cage, cage card, or even animal from a tagging mistake can jeopardize your colony and derail a protocol.
Increasing breeding efficiency helps reduce animal use and related costs; research animal facilities are increasingly accomplishing this goal with the help of digital tools.
Charles River has pioneered the development of integrated digital solutions to streamline the management of genetically modified colonies. Central to this innovation are the RapID Tags® scannable, color-coded ear tags and the ICM™ (Internet Colony Management) platform, which together allow precise identification and traceability of each animal. For instance, the revolutionary tool ICM™, a custom-designed software solution for both project and animal colony management, is a two-way, real-time communication system that provides comprehensive tracking of each animal, location, genotype, genetic background, procedural history, pedigree, and more. ICM™ simplifies record-keeping and enables control over colony sizes, which helps to reduce duplication.
Our GEMS teams at Charles River have begun using mini-colored mouse ear tags with scannable barcodes for lab animal identification. The hardened 2-D data matrix codes scan instantly with 100% accuracy, providing millions of unique IDs with zero errors. Digitalization has a beneficial effect on 3Rs by reducing the kinds of errors that lead to research failures and animal waste.
Enhancing this system further, the Live Tracking Management (LTM™) solution enables real-time monitoring and data collection throughout the animal’s lifecycle, from genotyping to study integration.
These interconnected platforms ensure seamless data flow, improve operational efficiency, and support refined animal welfare practices. Charles River’s digital ecosystem exemplifies its commitment to advancing research quality through smart, humane, and efficient colony management.