Chick Models and Human-Chick Organizer Grafts.

The combination of affordability, large size, and ease of access at almost every stage of development renders the chick an excellent model organism for studying vertebrate development. Not only is it a great system in and of itself, but these qualities make it a great host for interspecies chimera experiments. In this chapter we highlight some notable examples of mammalian-chick chimeras, and show how one can for instance use the chick to push mammalian stem cell experiments further to learn about the behavior and capabilities of these cells in vivo. In particular, here we present the methodology necessary for transplantation of human embryonic stem cell (hESC)-derived "gastruloids" stimulated to generate a human organizer into the chick embryo. In these human-chick chimeras, the human organizer cells self-organize to contribute directly to notochord-like tissue and indirectly induce host chick cells to generate neural tissue.