A key function of the Nieuwkoop center is to induce the formation of dorsal mesoderm. It turns out that the most dorsal mesoderm also functions as a signaling center, known as the Spemann Organizer. The difference between the Nieuwkoop center and the Spemann Organizer can be seen in transplantation experiments. Both signaling centers induce a [...]

BIlateral Asymmetry Vertebrates are bilaterally symmetric about the midline for many structures, like eyes, nasal passages, and limbs. However, most internal organs (including endodermal derivatives) are arranged asymmetrically in the abdominal cavity. Examples of Bilateral Asymmetry For example, the heart is on the ventral side. The lung has fewer lobes on this side to provide [...]

Localized mRNAs are critical early in embryogenesis to establish axes, and have been identified via molecular screening in frogs and genetic studies in Drosophila. Region Genes/Proteins Involved Effect Anterior/Posterior (A/P) Axis Bcd & Nos Hb, others Termini Torso Receptor Signal transduction cascade → Tailless, Huckebein (zygotic) Dorsal/Ventral (D/V) Axis Toll receptor Signal transduction cascade → [...]