Figure 33.9 The Dorsal Lip Induces Embryonic Organization
The findings from Hans Spemann’s early experiments in which he constricted fertilized salamander eggs with a baby’s hair led to the hypothesis that dividing cells in the early embryo each receive a different suite of cytoplasmic factors and that these factors lead to different developmental cell fates. The results from various transplantation experiments supported this idea and led Spemann and his student, Hilde Mangold, to expand upon his original hypothesis and propose that some cells can induce other cells to follow a specific developmental path. Continuing with transplantation experiments, Spemann and Mangold transplanted early gastrula dorsal lip material into the presumptive ventral epidermis of a host gastrula. The transplanted dorsal lip induced a second site of gastrulation in the host embryo, subsequent development of dorsal structures, and the formation of a complete secondary embryo attached to the first embryo. Today, we know that the formation of the secondary embryo from the ventral cells of the host arose as a result of signaling molecules present in the tissue commonly referred to as Spemann’s organizer. Recent studies have identified a number of factors that play a role in the inductive properties of the organizer. The precise mechanism by which the organizer region forms and directs the formation of the animal body plan, however, is the subject of on-going research.
Original Paper
Spemann, H., and H. Mangold. 1924. Über induktion von Embryonalagen durch Implantation Artfremder Organisatoren. Roux' Arch. Entw. Mech. 100: 599–638. Viktor Hamburger’s translation first appeared in Foundations of Experimental Embryology (B.H. Willier and J.M. Oppenheimer, eds.), Prentice Hall, Inc., Englewood Cliffs, N.J., pp. 146-184, 1964.
Links
Sander, K., and P. E. Faessler. 2001. Introducing the Spemann–Mangold organizer: experiments and insights that generated a key concept in developmental biology. International Journal of Developmental Biology 45: 1–11.
Fässler, P. E. 1996. Hans Spemann (1869–1941) and the Freiburg School of Embryology. International Journal of Developmental Biology 40: 49–57.
Dr. Hans Spemann: Nobel Prize in Physiology or Medicine 1935
Nature: Milestone 1 (1924): Organizing principles
Nature: Milestone 19 (1989): Chasing the elusive inducer
NCBI: Developmental Biology: Axis Formation in Amphibians: The Phenomenon of the Organizer
DevBio: A Companion to Developmental Biology: A Selective History of Induction II
Kimball’s Biology Pages: Organizing the Embryo: The Central Nervous System
R&D Systems: ADMP: A Ventralizing BMP in the Dorsal Embryo