All life features a complexity and harmony of purpose that can be difficult for us as mere humans to truly grasp. However, researchers have now been able to capture this complexity in 3D of an embryo turning itself inside out.
Using fluorescence microscopy, scientists from the University of Cambridge recently observed the first ever 3D images of an embryo conducting a vital process of gastrulation, which includes the organism turning itself inside out.
The British researchers observations were described in the journal Physical Review Letters and they reported how they were able to then test a mathematical model of morphogenesis, the process an embryo goes through to define the shape that it will become.
Gastrulation occurs during morphogenesis and is marked by when an embryo turns itself inside out from a sphere to a mushroom shape and back again. When the embryo folds inwards, it forms the primary germ layers, which then give rise to all of the body's organs.
In animals, gastrulation is a highly complex process that scientists have had difficulty understanding. Because of this, the team of researchers used embryos of a green alga called Volvox, because they undergo a similar process. However, Volvox embryos go through an additional process that animal embryos don't, they turn themselves right side out during the process.
According to the researchers, studying the Volvox embryos were ideal because they accomplish their transformation only by shifting cell shapes and the connections between the cells, which is simplistic when compared to the more complicated animal embryo gastrulation.
In the study, scientists described how the Volvox embryos start the process of inversion by folding inward around their middle, creating two hemispheres. Then, one hemisphere goes inside the other, forming an opening at the top that grows wider. Finally, the outer hemisphere slides over the inner hemisphere until the embryo reestablishes it's original spherical form.
"Until now there was no quantitative mechanical understanding of whether those changes were sufficient to account for the observed embryo shapes, and existing studies by conventional microscopy were limited to two-dimensional sections and analyses of chemically fixed embryos, rendering comparisons with theory on the dynamics difficult," said study author Raymond E. Goldstein, a biological physicist at Cambridge.
"It's exciting to be able to finally visualize this intriguing process in 3D," added co-author Stephanie Höhn, a cellular biologist. "This simple organism may provide ground-breaking information to help us understand similar processes in many different types of animals."
