Words and pictures can illustrate a lot about the world around us, but there’s nothing quite like video for putting reality in stark detail. And in the last few years, science fans have had an embarrassment of riches: new technology let scientists take video of bacteria harpooning DNA, cells moving through a living body, and a man talking … from the inside. Now, even newer visual tech is letting us see the development of an embryo at the cellular level, for the very first time. It’s not just cool — it’s also a breakthrough in our knowledge of biological development.
Let There Be Life
Lately, we’ve been getting really close to being able to grow organs in the lab or fix issues in developing fetuses. The problem is that we don’t exactly know what we’re doing — not entirely, anyway. Scientists have yet to figure out precisely how organs form in nature. If they knew where growing cells went and which genes turned on in the development of a liver, a brain, or a whole animal, they might be able to recreate it in a lab.
Kate McDole, a developmental biologist at Howard Hughes Medical Institute and first author on the new study, compared growing organs to constructing a building in an interview with ScienceNews. “If you took all the building materials for a house and threw them in a pile, you don’t magically get a house,” she said. “Contractors use plans to build the house.”
To uncover those plans, McDole and her colleagues used a technique called light-sheet microscopy, which uses sheets of light to illuminate the subject — in this case, a developing mouse embryo — and cameras to record the microscopic images. The research team equipped the cutting-edge microscope with a suite of algorithms that can track individual cells and determine how to get the best-looking images of their subject. That’s no small task for a complex embryo that’s growing rapidly. You can see the results below.
This is a clip from the first 48 hours of embryonic development when rudimentary organs start to form. The long horizontal structure forming at the center is called the neural tube, which forms the brain (at the left) and the spinal cord (at the right). Each blob you see is an individual cell.
Here’s the development of the spinal cord from another angle. In the leftmost image, it’s green; in the center and right images, it’s pink.
Plan Your Work, Work Your Plan
For the study, the team first collected a million images of each mouse embryo, following every cell over its first 48 hours. They then used that data to work backward, tracking where the cells in an 8.5-day old embryo had each originated. Without the cell-tracking and statistical programs they had developed, a task like that might have taken years. They used other programs to study an early stage in embryonic development called gastrulation, and others still to create a virtual mouse embryo that let them make comparisons between any two real embryos.
The breakthrough, which co-author Philipp Keller says is “literally a cellular-resolution building plan of the entire mouse,” builds on previous work the team had done with embryos of fruit flies and zebrafish. Now, it’s available to everyone: the microscope, computational tools, and imaging data are free for use by any researcher who wants it. If the body is a building, we’re this close to having the blueprints.