Cell Division implantation Cell Division implantation Cell Division implantation Cell Division implantation
The Biology

Our internal body organs and tissues, such as muscles, heart, kidneys and backbone, are made from a special cell layer called the mesoderm. This forms in the 2-week-old embryo from a unique structure called the Primitive Streak.   At this time the embryo is made of two layers of cells. To make the mesoderm, cells crawl from the top layer through the primitive streak to form a new, third, layer – which is a bit like the filling in a sandwich.

Film Cedit: Kees Weijer, University of Dundee
Images © Kate Storey

How it works

The inward movement of cells through the primitive streak is called gastrulation.

"It is not birth, marriage, or death, but gastrulation which is truly the important event in your life" - quote from famous Developmental Biologist Lewis Wolpert, spoken while convincing a clinician of the importance of studying early development.
(From his book 'The triumph of the embryo' Oxford University Press, 1993; now Dover 2008 www.doverpublications.com)

A key gene that controls gastrulation is called Snail. This gene ultimately directs the cellular machinery that controls cell movement. It causes cells packed tightly together in an epithelial sheet, to loose contact with each other and crawl through the primitive streak and move away as individual mesodermal cells. Secreted molecules, such as Fibroblast growth factors, also direct the movement of these cells.

Find out more:
Overview of human embryonic development leading up to primitive streak formation

Key labs that work on the Primitive Streak:
Claudio Stern, University College London

Guojun Sheng, Riken Institute, Japan

Kees Weijer, University of Dundee

Selected research papers:
A research paper investigating the mechanisms that control primitive streak formation

Review of the mechanisms underlying formation of the primitive streak

Review of recent research into the role of the primitive streak in embryonic development

Regulation of primitive streak position and twinning

Recapitulating early embryonic structures using human ES cells

When development goes wrong

Malformed backbone and ribs typical of the condition
known as VACTERL
Image © 2011 VACTERL Association Support Group  

If the mesoderm is not produced properly the embryo is unlikely to survive. The embryo will be miscarried so early that it will go unnoticed.

Occasionally, embryos survive with multiple problems in making the body parts that come from the mesoderm. The condition, known as VACTERL, can involve defects in the backbone, anus, heart, digestive and breathing systems, kidneys, arms and legs, some of which can be corrected by surgery.

Find out more:
The VACTERL Association is a support group dedicated to helping families affected by VACTERL/VATER Association based in the UK.

Primitive Streak Dress: details

The Primitive Streak is represented by two sheets of metallic silver cloth which feed into the central black groove at the back of the dress. A sheet of gold metallic fabric then indicates the mesoderm emerging between them. Rounded black plastic represents the top of the Primitive Streak.

Copyright Helen Storey


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