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Considerations for creating a custom research model: Insight from a scientist

Genetically engineered models and research breakthroughs can have a vast impact on the development of life-changing treatments. Specifically, when compared to existing models, custom models can be aligned to exact specifications through gene deletion, insertion, and other modifications.

To better understand our specific capacity to further your research objectives, we spoke with Justin Zhao, PhD, Principal Scientist at Envigo, who will share more about the scientific aspects of animal model generation and characterizations.

Evaluating the need for custom genetically engineered models

Dr. Zhao explained that the decision to use a custom model is very straightforward.

“If there is an existing model in our portfolio that will meet a customer’s expectations, we will make a recommendation based upon their research needs,” he said. “But if the customer wants to create their own model, for example, due to some license restriction issues, the customer could not access certain existing models outside of Envigo's portfolio, or the customer wants to make a unique modification to an existing model, then we can work together to create a custom model.”

Understanding custom model generation technology

“Some customers know exactly what they want, but not every customer is familiar with the technology for model generation,” said Dr. Zhao.

“We can help them choose the best option for their application by first meeting with their scientists to discuss their specifications. For example, if they need a humanized protein for certain genes, we learn about their desired application and typically optimize a human cDNA sequence. Other customers also need a mRNA sequence for targeting certain diseases. With that information, we can generate a customized scientific proposal that takes into account not only design of the model, but also application.”

Several different types of models are available.

“The easiest is the knockout model or point mutation model,” Dr. Zhao stated. “The other types include conditional knockout and knockin models. One type of knockin can use a safe harbor locus, where the expression is not affected by other genes and its insertion will not affect other genes as well. For those safe harbor loci, we have validated CRISPR gRNAs or Zinc Finger Nuclease (ZFN reagents, which can save some time.”

“Another is called humanization where human DNA is inserted into the rodent gene locus. We can also insert a reporter gene, for example, with fluorescent protein into the gene to see how and where genes are expressed in certain tissues.”

Dr. Zhao’s team also creates traditional transgenic lines to support research.

“Transgenic lines can be randomly inserted into any place. Those lines are useful for certain applications because they can have multiple copies and can achieve a very high expression level. It is also relatively easy to make a traditional transgenic line.”

Employing cutting-edge technology for custom models

“We use CRISPR-Cas9 based technology and ZFN technology,” said Dr. Zhao. “Our company is the first one to commercially use engineered endonuclease based technology to facilitate animal model generation. Engineered endonuclease cuts the genomic DNA at a desired site to introduce a DNA double-strand break (DSB). The DSB can be repaired either via non-homologus end joining (NHEJ), or via a homology-directed repair (HDR) pathway if a donor DNA is provided. Those two repair pathways can be harnessed to efficiently create knock out models and knockin models. Regardless of CRISPR, ZFN or TALENS, they all use the same 2 repair pathways. Compared to traditional ES-cell based gene targeting method, endonuclease-mediated knockout and knockin is more efficient and significantly shortens project timelines.”

Timelines for delivering custom model generation

The team at Envigo uses milestone-based pricing so clients pay for work based on the performance to date.

“We create a statement of work with each client so they know the strategy we are using along with the timelines with our milestones. We can also provide options for aggressive or conservative technologies, depending on the client’s needs and their budget requirements.”

Through the process, Dr. Zhao’s team and the client are supported by Envigo's scientific project management teams, who are themselves scientists with experience in creating and characterizing models, which strengthens the partnership with regular status updates.

“Beyond our regular meetings, we are also available to the client anytime they have a question,” he said.

Over the last 10 years, Dr. Zhao’s team has created thousands of different animal models. He remains passionate about sharing his scientific expertise and finding solutions that help meet specific customer needs—and helping researchers realize the full potential of their research.

Please contact us if you are interested in guidance for your custom model generation projects.