Choosing a Strain for Microinjection

In choosing a strain for microinjection, consider the genetic background of the strain, time constraints and cost. Good transgenesis rates are routinely achieved with B6SJLF1, FVB and C57BL/6. Founder mice produced in B6SJLF1 and FVB strains are generally easy to breed and have large litters ranging between 8-14 pups/litter. B6SJL is our recommended strain of choice when genetic background is not a concern.

If your studies involve breeding the newly generated transgenic lines to other established transgenic or knock-out lines, genetic background is potentially a concern and it is best to choose the most compatible, or genetically related, strain. Many knock-out lines are on a C57BL/6, 129 or mixed C57BL/6 X 129 background and thus, B6SJL mice would not necessarily be an appropriate strain for microinjections. It is common for established lines to have been backcrossed onto other genetic backgrounds and this information should be requested when ordering or obtaining mice from other investigators/institutions.

Finally, there is a growing body of evidence that background or modifier genes can significantly effect transgene expression. Literature may be available suggesting expression modulation of particular promoters but, more often than not, this information will not be known until different expression patterns are observed over time with different breeding schemes.

While there are hundreds of well-characterized mouse strains available today, relatively few are typically used for microinjection. The standard mouse strains available for microinjection through TTML include:

• B6SJL (C57BL/6 X SJL)F1
• FVB/N
• C57BL/6

It may be possible to use other strains if necessary for specific experiments, however, not all strains are suitable for microinjections. Many strains, such as SJL or 129, have poor reproductive capabilities while others, like BALB/c, do not incorporate injected DNA efficiently. Contact our lab for more information.