Replies to post #2499 on GTC Biotherapeutics (fka GTCB)

[Lewis R Goudy]

Could you guys review the glycosomal issues please?

chickens glycosylate their proteins with patterns more similar to humans than many other species do, including goats. Specifically, it is a matter of NGNA vs NANA side chains.

Is that the only dimension of similarity that matters?
Or are you saying the birds are advantaged there and not
disadvantaged otherwise so advantaged overall?

I remember also (I think it was in Meade's essay) that there
were some differences that affected PK but weren't an issue
re activity, could you address that in this context?

All clues welcome!

[gym gravity]

chickens-

I'm guessing the protein concentration of the egg white could be a barrier to producing some proteins, either by making some proteins harder to purify, or by creating a thermodynamically unstable environment that prohibits proper folding.

[used to make chicken]

The short answer is time.

GTCB and Pharming have been around a lot longer than any of the serious avian endeavors, which have been at it for about ten years. VRA doesn't count, because they are just throwing money at Roslin in hopes of slavation.

Chickens had some technical hurdles to overcome. Unlike mammals or fish or everything else, the chicken egg does not have a single pronucleus that you can inject. It has many, only one of which ends up being the correct one, so generating the initial mosaic transgenic is more of a numbers game. The primary obstacle however was finding a delivery system that would both 1) get the DNA of interest into the genome, and 2) do so in a way in which it was not "silenced."
Many genomes have ways of recognizing foriegn DNA and preventing any genes therein from expressing themselves. Lentiviruses were the ticket, and this has only been known for about 5 years.