Speed congenics

Genetically modified mice are an essential tool in research. The original background strain used to create the genetically modified mice can sometimes be inappropriate for a specific phenotypic analysis of the mutation. The transgene needs to be introduced to a more suitable genetic background. This can be done by marker assisted breeding, which means that a congenic strain can be generated in an accelerated fashion.

To create a congenic line it takes a minimum of 10 generations (backcrossing donor mice onto a recipient background to N10). At this point it is accepted that the gene of interest (allele) from the donor strain is then theoretically 99.9% identical to the recipient host inbred strain. In mice, this takes approximately 2–3 years to achieve. Speed congenics is an attempt to cut this time in half.

Often mice are generated on a mixed or genetically undefined background. Knockin/knockout mice produced by homologous combination are often produced on a mixed background (generally a mix of C57BL/6 and 129). Transgenic mice produced by pronuclear injection can also be produced on a F1 or F2 background. These animals may not be on the appropriate genetic background for researchers.

Also, the use of a congenic strain in research has several advantages over analysis on an undefined/mixed genetic background. It provides a defined experimental model for characterization as all the mice are genetically identical. This reduces experimental variability and in turn reduces the total number of mice needed per experiment.

Backcrossing mice for 10 generations to produce heterozygous N10 mice and then intercrossing these mice to produce homozygous mice is traditionally the way of developing a congenic strain. This typically takes 2-3 years to complete. Using a marker assisted/speed congenics screening approach this timeframe can be halved. Single nucleotide polymorphism (SNP) analysis at each generation will be used in order to generate a congenic strain on the desired genetic background in five generations.

Although there is initially extra cost involved in screening these mice, there is an overall reduction in the cost of producing a new congenic strain. These savings can be considerable because of the reduced animal numbers and reduced agistment costs (because of the reduced number). Speed congenic technology might give you a congenic strain in 12 to 18 months versus 2 to 3 years and research can be completed sooner with the strain.

Please contact us to discuss your individual project and your requirements.

TASQ registration form must be completed prior to service commencement.
A current AEC certificate and OGTR number must be supplied prior to commencement of service.
Work performed by TASQ will be invoiced by TASQ. AGRF will send their invoice direct to Client.
TASQ will not euthanase any WT or non breeding progeny/mice until written request from Client.

Costs

POA for Colony Management. Includes all breeding and monitoring of mice, record keeping, reporting to AEC, liaising with AGRF of samples and results.

Additional costs

Shipping charges of mice to TASQ (if applicable)
Wild type (WT) mice for the first F1 cross
Agistment of mice is not included in the speed congenic fee. Agistment is the weekly charge applied by the animal facilities for the basic care of the animal.

2024 External Clients: $26.00/cage/week

Internal Clients: Please contact TASQ for pricing.

Genotyping will be dependent on the work required from TASQ.
SNP analysis is performed by the Australian Genome Research Facility (AGRF). There is a minimum of 10 samples per run (POA).
Rederivation charges into clean facility (if applicable).
Shipment of mice back to Client (if applicable).

How to start

Breeding scheme

Mate animals (donor) containing genetic region of interest (transgene, knock-out gene, etc.) to animals of recipient strain to produce the F1 generation. If initial donor is homozygous, the F1 progeny will not have to be screened as they will all be heterozygous. If initial donor is heterozygous, the F1 progeny will have to be screened for heterozygous mice. All F1 progeny will be 50% recipient strain so it is not necessary to perform the SNP analysis. Recipient animals must be inbred and homozygous at the locus of interest.

Female donors are ideally used as the first cross so as to fix the Y chromosome on the recipient strain.

Mate heterozygous F1 males to females of recipient strain. This will fix the X chromosome. This will then generate the N2 generation. Progeny are screened for heterozygous mice. TASQ can perform the PCR screen or tissue sample or DNA can be sent to Client for PCR genotyping. Results must then be sent back to TASQ. These selected DNA samples are then sent for SNP analysis. Wild type animals will be euthanased.

Once N2 SNP results are returned to TASQ, 2-4 N2 males with the highest percentage of recipient strain will be selected to continue with the next cross with the recipient strain. N3 progeny are screened for heterozygous mice. TASQ can perform the PCR screen or tissue sample or DNA can be sent to Client for PCR genotyping. Results must then be sent back to TASQ. These selected DNA samples are then sent for SNP analysis. Wild type animals will be euthanased. Once N3 progeny are born all original donor mice will be euthanased unless Client requests all mice to be kept.

Once N3 SNP results are returned to TASQ, 2-4 N3 males with the highest percentage of recipient strain will be selected to continue with the next cross with the recipient strain. N4 progeny are screened for the heterozygous mice. TASQ can perform the PCR screen or tissue sample or DNA can be sent to Client for PCR genotyping. Results must then be sent back to TASQ. These selected DNA samples are then sent for SNP analysis. Wild type animals will be euthanased. Once N4 progeny are born all F1 donor mice will be euthanased unless Client requests all mice to be kept.

Once N4 SNP results are returned to TASQ, 2-4 N4 males with the highest percentage of recipient strain will be selected to continue with the next cross with the recipient strain. N5 progeny are screened for the heterozygous mice. TASQ can perform the PCR screen or tissue sample or DNA can be sent to Client for PCR genotyping. Results must then be sent back to TASQ. Once N5 progeny are born all N2 donor mice will be euthanased unless Client requests all mice to be kept.

At the N5 generation, >99% of the mouse’s genome should be derived from the recipient strain. These N5 mice can then be transferred to the Client. All mice derived through the backcross can be then euthanased.

If the Client requires a rederivation into a clean facility, this can be done at the N4 to N5 cross.