What is mouse cohort development?
Mouse cohort development is the planned breeding of a genetically engineered line to produce a defined number of animals meeting specified requirements for genotype, age, and sex. It encompasses breeding scheme design, breeding pair or trio setup and management, genotyping, weaning, age synchronization, and documentation for study use.
Colony management keeps a line alive. Cohort development produces the animals your protocol calls for. Most research programs need both, and we scope them together.
Where cohorts break down
Staggered cohorts
Animals are delivered in small groups over several weeks, leaving the study cohort with a wider age range than intended. In studies where age can influence the phenotype or experimental response, that variation introduces an additional biological variable and can complicate interpretation and experimental reproducibility.
Low genotype yield
Complex genotypes can occur at low expected frequencies. For example, an intercross between double heterozygotes can produce a double-homozygous target genotype at an expected frequency of 1/16 when the two loci assort independently. When the required genotype is further constrained by sex, the number of study-eligible animals per litter can be small. Breeding plans based on total litter numbers rather than expected genotype yield can therefore fall short of the required cohort size.
Linkage
When a floxed allele and a Cre driver are located on the same chromosome, they do not assort independently. If the desired allele combination requires recombination between the loci, its frequency depends on the recombination rate between them and can be substantially lower than the frequencies predicted for independently assorting loci. We check locus positions during breeding-scheme design, before pairs are established.
Genetic drift and colony quality
Genetic drift can accumulate over generations in independently maintained breeding colonies and may introduce genetic variation that affects phenotype and reproducibility. Appropriate colony management, genetic background monitoring, and periodic refreshment of breeding stocks can help maintain genetic consistency across cohorts and over time.
How we build a synchronized cohort
Step 1. Breeding scheme design
A PhD scientist reviews your allele, target genotype, control genotype, and study start date. We map the most efficient breeding path, check for linkage, and calculate how many breeding pairs are required based on expected genotype yield.
Step 2. Parallel breeding pair setup
Rather than breeding one pair and waiting, we establish multiple breeding pairs simultaneously and stagger breeding starts so litters are produced within a narrow, defined window. This approach helps generate a synchronized cohort with the required number of study-eligible animals.
Step 3. Genotyping and selection
Pups are genotyped using a validated PCR assay at weaning. Animals matching the experimental genotype and littermate control genotype are selected and tracked. Assay development is available for new or complex alleles.
Step 4. Age synchronization and release
Selected animals are held to your target age window, with male/female composition specified according to your protocol, and released as one cohort with genotype documentation and health certification.
Cohort specifications we deliver
- Target genotype and littermate control genotype, both confirmed by PCR
- Age matched delivery within a window you define
- Male/female composition specified according to your protocol, including balanced or single-sex groups
- Defined C57BL/6 background, with BALB/c and 129 available on request
- Multi allele and compound genotypes, including conditional systems
- Genotyping records, breeding pedigree, and health certification with shipment
- Staged release for longitudinal studies that enroll in waves
Send us your allele, target genotype, required n, and study start date, and a PhD scientist will return a breeding scheme and a schedule.
Request a Cohort PlanExpected genotype yields
These are expected Mendelian frequencies for unlinked loci. Actual yields vary with litter size, fertility, and, for linked loci, recombination frequency. We plan pair counts based on these expected frequencies and adjust the breeding strategy as needed based on early litter and genotype results.
| Cross | Target genotype | Expected frequency | Notes |
|---|---|---|---|
| Het x Het | Homozygous | 25 percent | Classic intercross, also yields 50 percent het |
| Het x Homozygous | Homozygous | 50 percent | Faster route when homozygotes are fertile |
| Flox/+ Cre/+ × Flox/Flox Cre−/− | Flox/Flox Cre/+ | 25 percent | Littermate control Flox/Flox Cre−/− also at 25 percent |
| Flox/+ Cre/+ x Flox/+ Cre/+ | Flox/Flox Cre/+ | 12.5 percent | Unlinked loci only |
| Any cross, linked loci | Target combination | Varies | Expected frequency depends on parental haplotypes and recombination rate; check locus positions first |
For C57BL/6 mice, gestation is approximately 19–21 days, weaning typically occurs at about 21 days, and breeding generally begins at approximately 6–8 weeks of age, depending on strain, sex, and colony conditions. A single generation typically requires several weeks from mating through weaning and selection of breeders. A three-generation breeding scheme to generate a homozygous conditional genotype can require several months, with the total timeline shaped by the starting genotypes, breeding strategy, genotype yield, and target study age.
Littermate controls
A cohort without proper controls is an incomplete deliverable. For conditional knockout work we breed and hold the Cre negative floxed littermates alongside the experimental animals, from the same crosses, in the same room, on the same schedule. Controls sourced from a separate colony introduce differences in microbiome, handling, and background that show up in your data.
Genotyping and documentation
Every animal released is genotype confirmed by PCR. For new alleles we design primers, optimize the assay, establish positive and negative controls, and document the protocol so your lab can run it after transfer.
Each cohort ships with a genotype report, a breeding record, and a health report.
The value of that oversight is documented in the peer reviewed literature: VanDenBerg KR, Oravecz-Wilson K, Krolikowski L, Hill V, Reddy P, Freeman ZT. Impact of Automated Genotyping and Increased Breeding Oversight on Overall Mouse Breeding Colony Productivity. Frontiers in Physiology, 2022. PMID 35923239.
Health status and transfer
All cohort breeding and holding takes place at our own facility in Holbrook, New York. Our facility operates under barrier conditions with HEPA filtered caging, autoclaved bedding and feed, controlled access, and routine sentinel testing for common murine pathogens. Incoming lines are quarantined and health tested before entering the main colony. Lines can arrive as live animals with health certification or as cryopreserved material.
Backgrounds and reproducibility
Cohorts are generated on a defined C57BL/6 genetic background to support consistency across replicates, sites, and studies. For lines arriving on a mixed genetic background, backcrossing progressively increases the proportion of the recipient background, with theoretical expectations of approximately 97% by N5 and more than 99% by N10. At sufficient backcross generations, the resulting line can be considered congenic.
Plan your cohort before you commit
Our Breeding Scheme Architect calculates expected genotype frequencies and the number of generations required to obtain a target genotype for a single allele. The tool is available at no cost and without an account. Use the results to estimate breeding requirements, then send us the output for review against expected colony performance.
What researchers say
“Our project manager did an outstanding job and has provided us with excellent customer service. Her availability to clarify issues has been nothing short of fantastic. I have recommended ingenious to others. Look forward for further collaboration on other projects.”
— Hamid M. Said, PhD, PharmD
University of California, Irvine
Frequently asked questions
Start your cohort plan
Send us your allele, your target genotype, your required n, and your study start date. A PhD scientist will return a breeding scheme and a schedule.
Request a Cohort Plan