Dear Martin,

This could result from either the induction or the Cre. I have heard of issues with the Cdh5-CreERT2 in different hands. Some claim that the Cre line produces a mosaic pattern of recombination. If it is the Cre it is best to switch to a better one. I am attaching a link that might help you optimize induction with tamoxifen. Park et al 2008 Dev Dyn 237: 447

(http://onlinelibrary.wiley.com/doi/10.1002/dvdy.21415/abstract;jsessionid=7605718733F9E3BC321E8404FC4E595E.f01t04)

Hope this helps

Krish

Dear Krish,

Thank you very much indeed for your remarks and the reference. I heard about some problems regarding the older VE-Cadherin-CreERT2 mouse line. Therefore I’m using the Cdh5(PAC)-CreERT2 line by Ralf Adams (http://www.ncbi.nlm.nih.gov/pubmed/20445537).

I think I’ll try an oral gavage as a route of administration instead of I.P, some authors claim that this approach leads to more robust results.

Kind regards,

Martin

We have noticed the same effect and have moved to oral gavage. It makes sense that embryos closer to the site of injection would received more of the drug

 Hi Martin, 

I am starting to work with Cdh5(Pac)-CreERT2, so I was wondering how your experience with them was like?

Also, for genotyping, I could just find a protocol to detect the transgene, therefore no possible classification between Cre-like homozigous or heterozygous. Were you able to sert that out? Or if not, would you say it is not that important to know the specific genotype of the mice as long as the express the Cre? Finally, would you say that the lox gene would be deleted in more or less the same proportation regardless the genotype of the mouse?

Thanks very much in advance,

Hi

I would suggest reading: VE-cadherin-Cre ERT2 Transgenic Mouse: A Model for Inducible Recombination in the Endothelium  Arnaud Monvoisin,1Jackelyn A. Alva,1,2Jennifer J. Hofmann,2Ann C. Zovein,1Timothy F. Lane,2,3and M. Luisa Iruela-Arispe.  These guys developed the original VE-Cadh-Cre ERT2 mouse.  Cre activation in young mice works fine, how ever there are a number of issues in aged mice described in the manuscript.  The efficiency of deletion is substantially reduced in older mice 24 weeks+.  This could be the result of a number of issues, Maturation or differentiation of the endothelial cells may influence the efficiency of the deletion, also it rare for the research lab to actually map the point of insertion, it could be related to its positioning.