Transgenic Mice – Genetic Research Models Accelerating Drug Development
Transgenic mice are important tools for scientists to study genetic disorders and human diseases. In this article, we review the basic information on transgenic mice research, application examples, and the development process for transgenic mouse models – serving as a guide for scientists looking to gain proper understanding of transgenic mouse models.
What are Transgenic Mice?
In general, transgenic mice are mouse models which have their genome altered through gene editing technology to include a foreign gene sequence, or transgene. Random transgenic mice are models that have foreign DNA materials randomly inserted into the genome with multicopy integration, but this leads to big variations in levels of gene expression in the offspring. To overcome this drawback, single-copy transgene integration may be achieved by cutting the gene at the ITR’s, so that only a single copy of the desired gene sequence integrates into the genome per TTAA site. This difference leads to a more consistent expression of the gene, while the integration into TTAA sites is associated with open chromatin – resulting in higher expression levels.
What Applications Are Transgenic Mice Used For?
Transgenic mice are widely used as animal models for understanding human diseases, accelerating drug development, and evaluating potential therapies. Genetic modification technology allows human genes to be transferred into mice, generating transgenic mouse models which are widely used for in vivo studies of human diseases. For example, scientists have used humanized ACE2 (hACE2) transgenic mice to investigate SARS-CoV-2 neutralizing antibody to develop vaccines effective against COVID-19.
How are Transgenic Mice Generated?
Let us move on to the steps of a pronuclear injection (PNI) and what happens inside the mouse genome as these steps progress:
To determine which offspring contain the gene, transgenic mice genotyping involves performing PCR testing on sample snippets of their tails. The mice that test positive for the transgene can be mated with other mice to establish lines of transgenic mice.
Pronuclear Injection and Random Integration of Transgene Constructs
To obtain transgenic mice via pronuclear injection (PNI), scientists must inject many zygotes with the transgene before implanting them into a surrogate mother. Although many of them will not be used, each one possesses the potential to turn into its own transgenic mouse line. In a traditional pronuclear injection (PNI), each of these zygotes will undergo a totally random integration of the transgene as it finds its way into the animal's genome. As noted in step 4 (above) of the PNI-based transgenic mouse model generation process, injection of the male pronucleus results in random integration of the transgene construct. Scientists think this may occur as DNA repair enzymes seek out and repair broken ends of DNA. However, the exact mechanisms for random integration have not yet been determined. This randomness includes the location of integration, how many different sites undergo integration, and how many copies of the gene are integrated into each site. These three major factors will lead to great varieties in the expression level of the offspring.
Comparison of Transgenic Model Generation Techniques and Capabilities
Rosa26 Targeted Transgenic
Random, multicopy integration
Random, single copy per integration site
Single copy transgene targeted to Rosa26 safe harbor locus
Transgenic plasmid or BAC
Transgenic plasmid or BAC
Targeting vector + gRNAs
Variable expression in founders
More consistent expression in founders
Most consistent expression
Can disrupt endogenous gene expression
Less likely to disrupt endogenous gene expression
Safe harbor site (SHS) does not disrupt endogenous gene expression
●Single-copy integration: Avoids potential gene silencing from multiple copies per integration site
●Defined region of integration: No loss of transgene sequence (TTAA, transcription unit)
●Reliability: More consistent expression pattern compared to plasmid-based transgenics
●Economical: Cost and turnaround time comparable to plasmid-based transgenics
Contact Cyagen for Transgenic Model Generation Support
From strategy design through to delivery of research-ready custom mouse models, Cyagen offers complete outsourcing for all your animal model needs. Cyagen’s gene editing services are unparalleled in efficiency of developing rodent models with a guaranteed genotype. We even offer price matching to help ensure researchers get the best deal for their study.
Contact usto perform your entire transgenic project - from initial strategy design and DNA vector construction, all the way through breeding – we deliver research-ready transgenic rodent models for guaranteed results.