Mouse - Axis formation

Question 1

What is the AVE?

Answer 1

• Migratory extraembryonic epithelia cells that in mammals control the AP axis
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Question 2

Neural Induction

Answer 2

• The entire brain has a common origin during early embryonic development in a single-layered pseudostratified epithelium called the neural plate (NP).
• Using embryological techniques such as single cell labeling and cell transplantations or genetic approaches (i.e., genetic tracing using mouse lines expressing Cre recombinase), the origins of the distinct components of the mature brain have been mapped in the early NP
• The study of anterior NP (ANP) specification, neural induc- tion, and antero-posterior (AP) axis formation are intimately linked.
• However, it came as a surprise that transplantation of the mouse node gave rise to an incom- plete axis lacking the anterior forebrain.
• An alternative explanation may be that the transplanting node only contained the posterior inducing activity, as does the late or trunk organizer of the amphibian embryo.
• The answer to this discrepancy observed in the mouse was simpler: the node/EGO did not contain all the infor- mation required to induce an entire neural axis because the anterior visceral endoderm (AVE) was necessary for anterior neural tissue to develop.
• Tissues equivalent to the mouse AVE, according to their location and molecu- lar expression patterns, exist in embryos of chick (hypo- blast), zebrafish (dorsal syncytial layer), and Xenopus (yolky cells of the vegetal pole), suggesting a conserved role in the vertebrate embryo
• However, the formation of the anterior neural plate does not exclusively rely on AVE activities and there must be cooperation with other signaling centers such as the gastrula organizers and axial mesendo- derm underlying the developing anterior neural plate.

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