cross of cre and flow mice - (Jul/02/2010 )
hi. i would like to ask about crossing strategies using cre and flox mice... I want to cross Tbx1-Cre mice with Tel flox/flox mice. I want to obtain Tel-/- mice. These are my questions:
1. is the Tbx1-cre mice i can obtain has the genotype Tbx1 cre/+ ?
2. how can i get Tel -/- mice?
I don't know anything about these specific genes, but.....
1) Your Tbx1-cre mouse will either be a heterozygote or a homozygote. You'll know based on the % of CRE+ offspring what the genotype was. 100%: it was homo. 50%: it was hetero. As with many transgenes, they don't seem to know where in the genome this is inserted, so you should avoid using homozygotes, since some important region of DNA might have been disrupted.
2) If you goal is to have Tel-/- mice, you might be better off getting a CMV-Cre mouse. In your Tbx1-cre mouse, Cre recombinase is expressed under the control of the Tbx1 promoter, so just certain tissues will contain Cre recombinase to excise the DNA between your loxP sites. This link seems to give the expression pattern.
I don't know if this expression pattern would lead to the production of gametes containing the recombined gene. I know CMV-Cre will, though.
If you can monitor the presence of your two loxP sites with PCR using forward and reverse primers. After recombination of your gene, you will be able to see the presence of the recombined (-) gene using the forward primer from the 1st loxP site and the reverse primer from the second loxP site. Try to generate a male and a female both containing this recombination product and breed them. 1/4 of the resulting offspring should then be Tel-/-, unless there is some kind of embryonic lethality. These will give the recombination product by PCR, but no product using the wild-type or loxP site PCRs. Do a PCR for CRE recombinase and pick a mouse that is negative.