Talking pets?

[Dodom]

Going back to how CRISPR isn't magic (and neither are ERVs in general, which would be the major case for "viral") altering expressed DNA in a meaningful way in an adult organism is another one of those things we can't really do. If you were doing this to humans (and good luck getting that past review boards) you'd basically have to use egg/sperm cells, and even then there's all sorts of potential issues.

Just look at the attempts of biohackers, and how they've accomplished approximately nothing.

For the previous example, glowing body secretion, it would be hypothetically possible to add that trait to a grown organism. We're not talking about a new structure, only a new chemical, a bit more complex than the dystrophin gene therapy currently in use(won't bother to look it up, but I assume that luciferin's synthesis requires multiple enzymes), but not by an impossible amount. It would have to be done via a viral vector, a modified retrovirus that would target the desired secretion cells (goblet cells? renal tubular cells?) and insert the selected genes.
And in a world where people had the ability to manufacture dubious cosmetic viral vectors, I imagine there would be rubbish, dangerous ones made. Right now, with only medical - and extensively tested - viral vectors, they still insert their payload in random locations on DNA. The risk of messing up the cell is acceptable given that those are made to cure terrible diseases, and the viruses are designed to be unable to replicate on their own. An imagined version made in someone's basement could keep its viral behaviour and cause disease and/or be contagious, new proteins added after the immune system is mature could cause the body to attack the modified cells, new synthesis products could cause a storage disorder if the body can't break them down, or the sloppy genetic alterations could cause cancer.
That could make a cool story though.


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Back to the original topic: Wouldn't it be more practical to develop modes of communication animals are already able to use with their current body and brain? Would a dog be able to associate concepts with pictures and tap them on a chart? Some service dogs are trained to speed-dial 9-1-1 if their human won't get up, so they can at least master the motions. Was it tried with more casual situations? Tap the solid triangle picture to say "follow me", that sort of things?