Speed congenic Services
The development of transgenic animals produces models with unsuitable or mixed genetic background making them inappropriate for biomedical studies. Historically, to resolve this problem, mutant animals are backcrossed onto wild type animals which have the desired inbred genetic background. In the backcrossing process, the presence of the mutation is monitored and it is expected that after 10 generations (from F1 to N10) the genetic background is inbred and that the mutation is fully integrated (congenic mice). 2 - 3 years are necessary to complete the process; in today’s competitive research arena, such a delay may be unacceptable.. The purpose of the speed congenic procedure is to significantly decrease the time required to transfer a mutation of interest from one genetic background (donor strain) to another (host strain - typically inbred).
Applying the speed congenic procedure, the transmission of the targeted mutation is first monitored as for backcrossing, but in addition the genome is scanned for polymorphic micro-satellites. Using this technique, only 5 generations (from F1 to N5) are required to obtain a congenic mouse. The process is complete in 10 to 14 months and the genetic background is at least 99% of the host strain genome.
For the animal strains involved in each project, a panel is designed consisting of 100 polymorphic microsatellites located throughout the genome and separated by 15 cM. The genome of 5 heterozygous mice per generation is scanned and the most suitable with respect to host genome content is used as founder for the next generation. The choice of the microsatellite panel is based on available databases and takes into account chromosomal location of the mutation. In the case of unavailability of a panel covering the entire genome the microsatellite analysis can be combined with specific SNP genotyping.
BV Transgenic Services is able to provide colony maintenance to microsatellite analysis.
Animals are maintained in flexible film isolators or IVCs. Tissue samples, usually tail snips, are treated for DNA extraction and analysed by PCR to detect the presence of the mutation according to the client protocol, and heterozygous animals are analysed for their homozygosity in host strain microsatellites. A significant portion of the genome of the two most suitable N5 animals is then scanned to monitor the quality of the speed congenic procedure.
Finally, at least these two heterozygous animals of high microbiological status will be returned to the customer in order to set up the new congenic colony. At each generation, an intermediary report is sent to the customer summarising the results of the microsatellite analysis, and the founder chosen for the next generation.
The significant advantage of the speed congenic procedure is the time saved (18 – 24 months) when compared with traditional backcrossing techniques.
By analysis of the genome at each generation, the most suitable founder for the next generation can be verified. In the traditional backcross technique, there are no such monitoring steps, which may lead to unexpected and undesirable outcomes. Our goal is to provide genetically verified models for your research.
What we need from the customer: