Primitive Streak

So I’ve been thinking a lot about the early stages of development (amazing what happens when you start teaching developmental biology instead of just focusing on the tiny aspect of development you’re interested in), and I’ve become rather fascinating with gastrulation and the ways in which the symmetry of a ball of cells is broken.

While preparing to teach axis formation, germ layers, and gastrulation, I was reminded of a line of clothing called “the primitive streak” that I’d learned about a few years ago while still a post-doc in London.

Several years ago two sisters, one a fashion designer in London and the other a biologist, teamed up to create a primitive streak inspired line of clothes. You can view the entire collection and learn a bit about the science that inspired the art at: http://www.primitive-streak.org/

For those more interested in the science, the primitive streak is a structure that establishes the embryonic axes and prospective midline in reptiles, birds, and mammals. It is the site of ingression for mesodermal and endodermal progenitors, which migrate to specific positions and differentiate into distinct germ layers and organs depending on when and where they enter the streak. The cells entering the streak appear to dance around the edge of the blastoderm and then move towards the center and down, very similar to speedy version of the Polonaise.

A network of signaling pathways work together to establish and then maintain the primitive streak. In the posterior marginal zone, Vg-1 (a member of the TGF-beta/BMP pathway) with Wnt/beta-catenin signaling activates Nodal expression. Nodal pathway activity, along with Fgf activity, is required for specification and migration of the streak and node. Nodal inhibitors are secreted by the streak, node, and hypoblast, ensuring that only a single embryonic axis forms.

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