I am planning to use CD4 Cre mice crossed with Loxp mice. However, the laboratory from which I am trying to get the loxp sperm says they have "the product of the EMMA ko crossed with the FLPe to make it a conditional knockout."
Why do they cross Loxp mice with FLPe mice? Is it to remove the neocassette? If so, why is the neocassette removed?
Can I use these mice to create conditional knockout mice by crossing them with CD4 Cre? What is the difference between Cre/loxp and FLP/FRT?
Dear Jiyoon Kim
I briefly wanted to reach out concerning your inquiry.
If I understand you correctly, I would say that the lab you want to obtain your mice from has converted a KO first (i.e. in IPMC/ EMMA speak Tm1a allele with promotor driven selection cassette) into a conditional KO (i.e. Tm1c allele).
They crossed your Tm1a KO first with FLP recombinase mice to get rid of the neocassette as this often has long-range off-target effects on the expression of other genes (not necessarily in the vicinity of your gene of interest).
For details on the different knock-out strategies, please see:
https://www.mousephenotype.org/understand/start-using-the-impc/allele-design/
Without more details concerning the construct, I can not tell, if example 1. or 2. are representative for your specific case.
For an example aiming to systematically assess the off-target effects (on gene expression) associated with the neomycin resistance cassette, please see:
Article Transcriptome Analysis of Targeted Mouse Mutations Reveals t...
For a simple introduction into the differences between the Cre/lox and the Flp/frt systems, please see:
https://www.jax.org/news-and-insights/2006/may/the-cre-lox-and-flp-frt-systems
And lastly, as you seem, to have a very similar conditional knock-out strategy in mind for your gene of interest that I used during my postdoc, please see the attached publications, for detailed genotyping protocols (for Tm1a and Tm1c/d), mouse breeding instructions and characterization of the CD4 & LCK Cre mouse strains.
Article The critical role of histone H2A-deubiquitinase Mysm1 in hem...
Article Deubiquitinase MYSM1 Is Essential for Normal Fetal Liver Hem...
Article A role for the histone H2A deubiquitinase MYSM1 in maintenan...
I hope that helps.
All the best & good luck with your experiments,
Michael