A key regulator of early body axis formation appears to be the localized expression of the protein Nodal (see Factors- Nodal) at the primitive streak stage of development. Nodal is a TGF-beta related protein and is specifically expressed at the node of the primitive streak (hence its name) during gastrulation. Its role appears to be to differentiate mesoderm as it migrates through the primitive streak and in doing so it also patterns axis formation.
Human embryo (stage 7) Viewed from surface ectoderm, shows primitive streak. Node occurs at the righthand end of dark streak.
(connecting stalk is to the left)
Factors- Nodal, Swiss Protein Entry- Nodal (mouse)
Left/Right
The first page of Developmental and System Notes usually contains some information about mechanisms of development that include molecular mechanisms. In order to keep the introductory page simple, detailed molecular mechanisms have been placed on a separate page (Page 11) of each section of notes. Below is a list of direct links to specific Molecular Development Pages.
| Molecular System Notes |
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| Axis Formation | Early | Limbs |
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Signaling during development, though complex, can also be grouped into a few specific classes. These mechanisms have also been listed and described briefly on Signaling Mechanisms page.
Lecture Notes |
Please note that these notes only relate to an earlier Course and not all Lecture notes and research material have been transferred. |
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Simple pictures illustrating the early events of fertilization. |
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Figures and text relating to early events of spinal cord formation. |
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Text relating to the molecular events of sex determination in the embryo. |
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A short comparison of establishing positional information in embryos. |
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The fly mutation that opened the field of Hox Genes and the conservation of pattern formation control mechanisms between species in embryonic development. |
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Home Page
Embryo stages
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K12 Students
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Molecular Development
Axes Formation
Early Axis
Rostro/Caudal Axis
Anterior/Posterior Axis
Left/Right Axis
Limb Axes
School of Med Sci
UNSW Medicine
University of NSW
UNSW Cell Biology
NCBI Books
Dev Biol (Gilbert)
This section of notes introduces the topic of axes formation which establishes body patterns in multicellular organisms.
While the final animals are significantly different, the mechanisms that regulate axis formation have common molecular pathways and signals.
An excellent example is the patterning of the limb, which has been a model for axis formation.
Molecular mechanisms of development is an exciting area and requires a variety of different skills. This page introduces only a few examples and should give you a feel for the topic.
Please email Dr Mark Hill if you wish to make a comment about this current project.