Cell division breakthrough
Image: Drosophila synaptonemal complex forms as two distinct layers that mirror each other [Ryan Kramer]
US-based researchers have combined super-resolution and expansion microscopy to solve the 3D structure of a complex, essential for sorting chromosomes into eggs and sperm during reproductive cell division or meiosis.
When this synaptonemal complex doesn't assemble properly in the cell, it can lead to chromosomal abnormalities, miscarriages, and birth defects.
Since the complex was first discovered in 1956, researchers have been trying to identify its many moving parts and how they fit together, but the structure has been too small to visualise with most microscopes.
However, Professor Scott Hawley from the Stowers Institute for Medical Research, and colleagues, combined super-resolution and expansion microscopy to render the likeness of this enigmatic structure in Drosophila.
"The structure was so much more complicated and beautiful than we ever imagined," says Hawley. "We thought it just looked like a railroad track, but we discovered that it is actually more like two railroad tracks, one stacked on top of the other."
"This changes the way we think about this structure and what it does," he adds.
Hawley and colleagues first gathered samples of the synaptonemal complex from dissected fruit fly ovaries, and embedded these in a gel, added liquid, and watched the samples expand fourfold.
They then used structured illumination microscope to study the enlarged samples.
They discovered that the structure was divided into two identical but distinct layers, which had been indistinguishable at lower resolution.
"This was a really incredible insight, a technical leap using this new methodology of expansion microscopy and merging it with structured illumination to create a way to look at a structure that hasn't been resolved before," says Hawley.
"There is a lot more we can learn. The deeper we dive into structure, the more complexity we see, the more amazing the structure becomes," he concludes. "Structure provides so much insight into function."
Research is published in PNAS.