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Monday, November 20, 2006

RNAi Mice

From Biospace:


Artemis Pharmaceuticals GmbH, Cologne announced today that it has signed a research agreement with Merck & Co., Inc. to construct a large number of shRNA interference genetically engineered mouse models (1) for the in vivo functional analysis of selected disease related genes. The agreement represents a significant initiative to undertake a large-scale approach to gene function analysis using shRNA knock down in genetically engineered mice as models (2) for human biology.


Under the terms of the agreement, Artemis will generate genetically engineered shRNAi "knock down" mouse models (3) for Merck using Artemis' proprietary, optimized and fully integrated vector construction, ES cell transfection and inducible RNAi technology (4). Merck will provide selected shRNA sequences that correspond to mouse genes that may also play a central role in human diseases. Artemis will use its technologies to achieve constitutive as well as inducible functional down-regulation of the expression of the gene targets provided by Merck (5).


Artemis is the first company to have developed a robust methodology for the controlled induction of shRNA based gene knock down (6) in adult mice. This inducible system permits the down-regulation of a selected target gene to be turned on and off thereby more closely modeling the dosing of a pharmacologic inhibitor. The generation time for such a mouse model at Artemis is only four months.


From Cargo Cult Scientist:


What are the six highlighted groups of words saying?


1. shRNA interference genetically engineered mouse models The mice generate siRNA that KOs a gene?

2. using shRNA knock down in genetically engineered mice The mice have been engineered to produce a constant amount of a certain gene product that can be KOd by adding siRNA?

3. genetically engineered shRNAi "knock down" mouse models The model constituatively produces siRNA and it's target?

4. inducible shRNAi mouse models The model constituatively produces siRNA and it's target?

5. constitutive as well as inducible functional down-regulation of the expression of the gene targets They can regulate the expression of a gene target and thus better measure the effects of siRNA that will be delivered much in the way the siRNA drug will be delivered in humans?

6. controlled induction of shRNA based gene knock down They can control the induction of the siRNA that has been engineered into the mouse?


I went to the Artemis website to figure this out.
First they clone in the siRNA sequence that will knock out an endogenous gene product. They are using Taqman to measure mRNA levels. Let's assume that this is the accepted method of measuring RNAi knock down. Wouldn't a better control be to not induce the RNAi in one mouse and induce it in another. That way you are comparing the effects of RNAi and not two genetically different mice. According to Artemis:

Using a reporter system, we have demonstrated that in our system constitutive RNAi knock down of over 80% can be achieved in almost all tissues of the body. Of what protein?
This knock down has been shown to be stable over at least 25 weeks and is inheritable into the next generation. At 80% KO strength?
Development of a system to efficiently produce RNAi knock down mice within 4 months. Why does it take less time than making other genetically altered mice?
We have shown that RNAi-based constitutive knock down of endogenous genes can reproduce the phenotype of the corresponding conventional gene KO. Such as???
We'd all like to have mice that make any protein you want and that could easily be measured. Add something you think will kill it off and start piling up the data. It's not real. Time will tell. This goes on the list of Cargo Cult Science projects. Too many questions have been left unanswered. It has all of the signs. We've got measurements that hitherto have been unable to nail down. We've got data on an unknown gene but claims of 80% KO in all tissues. And we've got the one chart with two bars, one taller than the other. It's a dead give away. Stay tuned.

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