Hello,

Can you provide more information about these strains? 

According to this article, knock in and TR means the same, but I am not sure which APOE knock in and TR strains you are asking about.

http://www.hindawi.com/journals/ijad/2011/810981/

Apoe transgenic mice contain the human apoE in addition to their own apoE gene. The knock-in mouse is a model where the mouse apoE is exchanged against a specific human apoE genotype (for example see

http://www.ncbi.nlm.nih.gov/pubmed/10655544, the authors created an apoE4 transgenic mouse). In the later model apoE is expressed in all tissues expressing apoE regularly in mouse whereas the expression in "normal" transgenic mice depends on the used promoter. If this is an ubiquitous promoter you will find apoE in every cell, by choosing an organ specific promoter you can limit the apoE expression. 

I am not sure that TR means transgenic. Looks like TR = "Targeted Replacement".

Thank you，Maria. TR means target replacement.I guess they are the same.When the published paper used mice strains from Taconic,they would always say TR,and if they knock-in themselves ,they would say knock in.Am I right?

Thank you ,Michael.According to your explanation,I guess they are the same.