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It was a game changer in terms of making things cheaper and a little easier. However the actual functionality was still possible with other methods. Zinc finger nucleases for example. Knockdown via RNAi is often still done because a knockout target may be inviable, and it is pretty cheap and easy to knockdown in most model systems.
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I disagree that it's "gene therapy" to affect the natural regulation of mRNA production. If that were true then the term "gene therapy" loses its meaning, as just about everything changes the expression of mRNA. You can probably do so somewhere just by thinking really hard about it.

Expressing mRNA that doesn't exist in the genome, that would be gene therapy. Or just a virus.

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Edit every cell? No. Edit enough cells to impact health outcomes for a meaningful period of time? [Yes](https://www.youtube.com/watch?v=J3FcbFqSoQY)
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This approach can work for some genetic diseases such as blindness based on some cells in the retina or partial blindness. For others this is not really a cure. If you want to cure people with progeria, does curing 20% of the cells really help? Perhaps 100% is not necessary, but it would seem strange to cure only some cells but not others. You'd have a mosaic of cells where some would work and others don't. Cells interact; timing also plays a role in development. I don't really see that aiming for anything but a very high number of cells cured, can work.
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