Mouse Strain Rederivation


General Description


The integrity of a GEM facility is dependent upon the ability to maintain the mouse colony in a specific pathogen free (SPF) state. Therefore, when BCM investigators desire to import mouse strains from facilities that are not SPF or when an outbreak of contamination occurs in a mouse colony, the GERM Core will help investigators to rederive their mouse strains using embryo transfer to recipient SPF female mice.

What Will Happen

  1. Investigator will submit a request form through iLab, filling out information on the number and age of male and female mice to be used. An account number and IACUC protocol number must be provided at this time. The investigator’s IACUC protocol must be approved for all procedures performed in the Investigator laboratory.
  2. The core will review the investigator provided information and approve the request. The core will schedule the mouse strain rederivation according to the female mouse age and coordinate with the investigator or CCM if the mice are in quarantine.
  3. Investigators will complete the following steps to prepare embryos:
    • a. Investigator prepares 2+ adult males and 2-4+ young female mice at 3.5-5 weeks of age and of the appropriate genotypes.
    • b. One week before the scheduled rederivation date, pick up 1 tube of M2 media, 1 tube of PMSG, and 1 tube of HCG from the GERM Core (Location for pick up: N630.01 in Alkek Bldg.). Note: Bring an ice bucket to put the hormones in and put them in a -20C freezer when you get back to your lab. Dilute the hormones right before you go to give the injections.
    • c. PMSG is administered via intraperitoneal injection (IP), at 10 a.m. three days before the scheduled rederivation date (e.g. Tuesday for rederivation on Friday). Dilute the PMSG with 950 ul of 0.9% saline and administer 0.1cc IP per mouse.
    • d. HCG is administered via IP injection 47 hours after PMSG, at 9 a.m. one day before the scheduled rederivation date (e.g. Thursday for rederivation on Friday). Dilute the HCG with 950 ul of 0.9% saline and administer 0.1cc IP per mouse.
    • e. Place the females with the males immediately after administering HCG.
    • f. The morning following the HCG injections, the females are removed from the male cages and oviducts are collected into M2 media provided by the GERM Core.
    • g. Label the tubes with the iLab request number. Deliver the oviducts to ABBR R119A and leave in the biosafety hood at room temperature no later than 9 a.m.
  4. The core will dissect, digest, and collect all oocytes from the oviducts, identify and transfer all fertilized 1-cell embryos to pseudo pregnant recipient ICR female mice to allow gestation.
  5. Live-born founder animals will be held by the GERM Core until 10-14 days of age and subsequently transferred to the investigator.

What is Expected

The GERM core will transfer all 1-cell embryos to 0.5-day pseudo pregnant recipient mice.

The number of expected live-born offspring will vary and will be dependent on the number of embryos transferred. On average, 15-20% of transferred embryos result in live-born offspring.

If there are no fertilized embryos collected, the core will charge 40% of cost. Investigators can repeat the rederivation at 100% cost.