11 replies to this topic

[MrHappy]

http://www.nature.co...ature11438.html
"
...Here we demonstrate that the aged muscle stem cell niche, the muscle fibre, expresses Fgf2 under homeostatic conditions, driving a subset of satellite cells to break quiescence and lose their self-renewing capacity. We show in mice that relatively dormant aged satellite cells robustly express sprouty 1 (Spry1), an inhibitor of fibroblast growth factor (FGF) signalling. Increasing FGF signalling in aged satellite cells under homeostatic conditions by removing Spry1 results in the loss of quiescence, satellite cell depletion and diminished regenerative capacity. Conversely, reducing niche-derived FGF activity through inhibition of Fgfr1 signalling or overexpression of Spry1 in satellite cells prevents their depletion. These experiments identify an age-dependent change in the stem cell niche that directly influences stem cell quiescence and function.."

[nowayout]

Not sure what to make of this article. Their use of tamoxifen is not explained or motivated. What are they using it for exactly?

Edited by viveutvivas, 28 September 2012 - 01:57 PM.

[MrHappy]

Not sure what to make of this article. Their use of tamoxifen is not explained or motivated. What are they using it for exactly?

Promoting FGF by some mechanism.

[niner]

Not sure what to make of this article. Their use of tamoxifen is not explained or motivated. What are they using it for exactly?

Promoting FGF by some mechanism.

Tamoxifen is used as a trigger in conditional expression constructs in genetically modified animals. I don't have access to the full paper, but in the figure captions that were available on the Nature web site, I did see a reference to wild-type animals, suggesting that there is a genetically modified one that they are comparing it to. So.. my guess is that tamoxifen would only work like this in animals with the appropriate genetic mods.

[nowayout]

Tamoxifen is used as a trigger in conditional expression constructs in genetically modified animals. So.. my guess is that tamoxifen would only work like this in animals with the appropriate genetic mods.

Aha. So it will do nothing like that for humans.

Also, the title of the thread is a little misleading if your interpretation is correct.

[MrHappy]

Here's another paper (full). Different study - this one is on myelination and tamoxifen. They are also using GM mice, which don't produce FGF. After reading this and a few other studies, I would say this looks interesting enough for clinic trials. It's already used in humans for breast cancer, etc.

http://digitalcommon...arch="tamoxifen fgf"

Edit: tapatalk, big thumbs.

Edited by MrHappy, 30 September 2012 - 10:12 PM.

[nowayout]

Here's another paper (full). Different study - this one is on myelination and tamoxifen. They are also using GM mice, which don't produce FGF. After reading this and a few other studies, I would say this looks interesting enough for clinic trials. It's already used in humans for breast cancer, etc.

http://digitalcommon...arch="tamoxifen fgf"

Edit: tapatalk, big thumbs.

You don't understand. These animals were genetically altered (programmed) to respond to Tamoxifen in a specific way. Tamoxifen is used to trigger the genetically altered program. Humans don't have such a genetic alteration, so Tamoxifen will do nothing like this for humans.

Edited by viveutvivas, 30 September 2012 - 10:18 PM.

[MrHappy]

Here's another paper (full). Different study - this one is on myelination and tamoxifen. They are also using GM mice, which don't produce FGF. After reading this and a few other studies, I would say this looks interesting enough for clinic trials. It's already used in humans for breast cancer, etc.

http://digitalcommon...arch="tamoxifen fgf"

Edit: tapatalk, big thumbs.

You don't understand. These animals were genetically altered (programmed) to respond to Tamoxifen in a specific way. Tamoxifen is used to trigger the genetically altered program. Humans don't have such a genetic alteration, so Tamoxifen will do nothing like this for humans.

I thought they were programmed not to produce FGF?

[nowayout]

Here's another paper (full). Different study - this one is on myelination and tamoxifen. They are also using GM mice, which don't produce FGF. After reading this and a few other studies, I would say this looks interesting enough for clinic trials. It's already used in humans for breast cancer, etc.

http://digitalcommon...arch="tamoxifen fgf"

Edit: tapatalk, big thumbs.

You don't understand. These animals were genetically altered (programmed) to respond to Tamoxifen in a specific way. Tamoxifen is used to trigger the genetically altered program. Humans don't have such a genetic alteration, so Tamoxifen will do nothing like this for humans.

I thought they were programmed not to produce FGF?

Whatever they were programmed to do, it is a program artificially inserted on purpose in the genetically modified mice to be triggered by tamoxifen, so that they can use tamoxifen to modulate the activity of whatever gene they programmed the mouse to activate/deactivate in response to tamoxifen - the choice of tamoxifen for this is quite arbitrary, since many other substances could have been used as the trigger. Wild type mice (or humans) do not have that artificial program, so tamoxifen will do nothing like that for them (or us).

Here is some more information on the technique:

Dev Biol. 2002 Apr 15;244(2):305-18.
Efficient recombination in diverse tissues by a tamoxifen-inducible form of Cre: a tool for temporally regulated gene activation/inactivation in the mouse.

Hayashi S, McMahon AP.

Source

Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA.
Abstract

In recent years, the Cre integrase from bacteriophage P1 has become an essential tool for conditional gene activation and/or inactivation in mouse. In an earlier report, we described a fusion protein between Cre and a mutated form of the ligand binding domain of the estrogen receptor (Cre-ER) that renders Cre activity tamoxifen ™ inducible, allowing for conditional modification of gene activity in the mammalian neural tube in utero. In the current work, we have generated a transgenic mouse line in which Cre-ER is ubiquitously expressed to permit temporally regulated Cre-mediated recombination in diverse tissues of the mouse at embryonic and adult stages. We demonstrate that a single, intraperitoneal injection of TM into a pregnant mouse at 8.5 days postcoitum leads to detectable recombination in the developing embryo within 6 h of injection and efficient recombination of a reporter gene in derivatives of all three germ layers within 24 h of injection. In addition, by varying the dose of TM injected, the percentage of cells undergoing a recombination event in the embryo can be controlled. Dose-dependent excision induced by TM was also possible in diverse tissues in the adult mouse, including the central nervous system, and in cultured cells derived from the transgenic mouse line. This inducible Cre system will be a broadly useful tool to modulate gene activity in mouse embryos, adults, and culture systems where temporal control is an important consideration.

Edited by viveutvivas, 01 October 2012 - 08:37 PM.

[MrHappy]

Here's another paper (full). Different study - this one is on myelination and tamoxifen. They are also using GM mice, which don't produce FGF. After reading this and a few other studies, I would say this looks interesting enough for clinic trials. It's already used in humans for breast cancer, etc.

http://digitalcommon...arch="tamoxifen fgf"

Edit: tapatalk, big thumbs.

You don't understand. These animals were genetically altered (programmed) to respond to Tamoxifen in a specific way. Tamoxifen is used to trigger the genetically altered program. Humans don't have such a genetic alteration, so Tamoxifen will do nothing like this for humans.

I thought they were programmed not to produce FGF?

Whatever they were programmed to do, it is a program artificially inserted on purpose in the genetically modified mice to be triggered by tamoxifen, so that they can use tamoxifen to modulate the activity of whatever gene they programmed the mouse to activate/deactivate in response to tamoxifen - the choice of tamoxifen for this is quite arbitrary, since many other substances could have been used as the trigger. Wild type mice (or humans) do not have that artificial program, so tamoxifen will do nothing like that for them (or us).

Here is some more information on the technique:

Dev Biol. 2002 Apr 15;244(2):305-18.
Efficient recombination in diverse tissues by a tamoxifen-inducible form of Cre: a tool for temporally regulated gene activation/inactivation in the mouse.

Hayashi S, McMahon AP.

Source

Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA.
Abstract

In recent years, the Cre integrase from bacteriophage P1 has become an essential tool for conditional gene activation and/or inactivation in mouse. In an earlier report, we described a fusion protein between Cre and a mutated form of the ligand binding domain of the estrogen receptor (Cre-ER) that renders Cre activity tamoxifen ™ inducible, allowing for conditional modification of gene activity in the mammalian neural tube in utero. In the current work, we have generated a transgenic mouse line in which Cre-ER is ubiquitously expressed to permit temporally regulated Cre-mediated recombination in diverse tissues of the mouse at embryonic and adult stages. We demonstrate that a single, intraperitoneal injection of TM into a pregnant mouse at 8.5 days postcoitum leads to detectable recombination in the developing embryo within 6 h of injection and efficient recombination of a reporter gene in derivatives of all three germ layers within 24 h of injection. In addition, by varying the dose of TM injected, the percentage of cells undergoing a recombination event in the embryo can be controlled. Dose-dependent excision induced by TM was also possible in diverse tissues in the adult mouse, including the central nervous system, and in cultured cells derived from the transgenic mouse line. This inducible Cre system will be a broadly useful tool to modulate gene activity in mouse embryos, adults, and culture systems where temporal control is an important consideration.

Thanks, that makes much more sense! In which case the title needs to be altered - replace TM with FGF.

[niner]

OK, I fixed the title.

[MrHappy]

OK, I fixed the title.

Ta, muchly.