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Analytical Chemistry

Revealing 3-D organization of meiosis complex

Combining two kinds of microscopy reveals a layered structure in the synaptonemal complex

by Celia Henry Arnaud
August 7, 2017 | A version of this story appeared in Volume 95, Issue 32

An artist’s model showing the arrangement of four kinds of proteins in the synaptonemal complex, which has two layers that connect strands of DNA.
Credit: Proc. Natl. Acad. Sci. USA
A proposed 3-D model shows how multiple proteins (pink, brown, blue, and green) in the fruit fly synaptonemal complex are arranged relative to one another. The gray sheets represent proteins that weren’t included in this study. The gray loops represent the DNA strands.

A multiprotein structure called the synaptonemal complex helps chromosomes segregate properly during the cell division process known as meiosis. Although much is already known about the proteins in the complex and their two-dimensional arrangement, the 3-D organization of the complex is less well understood. Now, a team led by R. Scott Hawley, Brian D. Slaughter, and Jay R. Unruh of Stowers Institute for Medical Research has combined two microscopy techniques to get a better 3-D picture of the fruit fly version of the complex (Proc. Natl. Acad. Sci. USA 2017, DOI: 10.1073/pnas.1705623114). The researchers modified a technique called expansion microscopy to make it compatible with superresolution microscopy. In expansion microscopy, a gel matrix with an embedded sample is uniformly inflated, which separates the components in the sample while keeping them correctly oriented relative to one another. To use the method with superresolution microscopy, the researchers modified the method so they could thinly slice the samples after embedding them in the matrix but before expanding the matrix. They expanded the samples to about four times their normal size. Then they acquired images using a superresolution microscopy method called structured illumination microscopy. The images revealed that the complex has two layers that mirror each other. The researchers propose that the layers possibly connect a sister chromatid (one of two identical copies of a replicated chromosome) from one homologous chromosome to a sister chromatid of the other homolog.


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