Abstract
Germ layer specification and axis formation are crucial events in embryonic development. The Spemann organizer regulates the early developmental processes by multiple regulatory mechanisms. This review focuses on the responsive signaling in organizer formation and how the organizer orchestrates the germ layer specification in vertebrates. Accumulated evidence indicates that the organizer influences embryonic development by dual signaling. Two parallel processes, the migration of the organizer’s cells, followed by the transcriptional activation/deactivation of target genes, and the diffusion of secreting molecules, collectively direct the early development. Finally, we take an in-depth look at active signaling that originates from the organizer and involves germ layer specification and patterning.
Highlights
In 1924, to understand the processes involved in developmental biology, Spemann and Mangold transplanted a blastopore lip between different ectodermal regions of amphibian embryos [1]
This species-specific organizer (s) secrete molecules are most common across the vertebrates, including bone morphogenetic proteins (BMPs), Wnt, and Nodal inhibitors [6], and forms prechordal plate and notochord [12,32]
The ventral center has a high level of signaling by BMP4 and BMP7, which bind to membrane BMP receptors (BMPR), which subsequently phosphorylate the C-terminal of Smad1, activate Smad1, which is translocated to the nucleus, and activate certain target 9genes critical to early development [105,110]
Summary
In 1924, to understand the processes involved in developmental biology, Spemann and Mangold transplanted a blastopore lip between different ectodermal regions of amphibian embryos [1]. Spemann and Mangold discovered the organizing center in the dorsal blastopore lip of amphibians [1] This center consists of a cluster of cells in the developing embryo that have the ability to interact and instruct morphogenesis in the surrounding cells during gastrulation [3]. Spemann and Mangold found the first evidence of the organizing center, thereafter called the “Spemann organizer”, and its major role in the development of vertebrates This discovery introduced the concept of induction in embryonic development, which refers to the method used by specific cells to affect the fate of other embryonic cells [1,2,3]. Which is a germ criticallayers, step in the development of all Figure 1
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