Mouse Models


The generation of genetically modified mice may be divided into two main categories: targeted integration (insertion or deletion) and random integration of DNA into the mouse genome. In the first category, gene targeting is typically performed in embryonic stems (ES) cells and is ideally suited to deletion (or modification) of endogenous alleles. The MBP also uses newer genome editing technologies (e.g., CRISPR/Cas) to create knockout and knockin mice at lower cost and in significantly less time than conventional, homologous recombination-based approaches in ES cells.  In the second category, pronuclear injection generates transgenic mice by random integration of DNA (e.g., LacZ, GFP, etc) into the mouse genome. 

Your specific scientific hypothesis-driven question will drive which approach to use to create the most appropriate mutant mouse model for research. 


Comparison of ES cell Targeted, Transgenic and CRISPR gene modification systems 

ES cell models


Random Transgenesis









Site specific integration, no unintended disruption of endogenous gene function.

Increased time to generate founders due to cell culture and germline transmission from chimeras.

Lower overall project cost compared to ES cell based targeting.

Unpredictable insertions sites. Endogenous gene disruption that may lead to confounding phenotypes.

Lower overall project cost compared to ES cell based targeting.

Low flexibility in model design and transgene insertion size.

Single copy insertion of gene construct, rarely undergoes gene silencing.

Higher overall project cost of compared to random transgenics and CRISPR.


Rapid generation of founders.

Multiple insertion sites and/or copy number leading to diminishing expression or silencing.


Shorter project timeframe. In general, KO creation using CRISPR/Cas9 can create an InDel in 1/3 the time of traditional ES cell targeting

Off target effects need to be identified and bred out in subsequent generations

Stable integration and germline transmission.

Limited to genetic background of available, germline competent, ES cells.

Not limited by genetic background

Multiple independent founders may be necessary to identify the desired expression pattern.

Not limited by genetic background. The MBP has high success using the CRISPR/Cas9 platform in  C57BL/6 genetic backgrounds





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