Using light microscopy to study developmental processes in situ is a bit tricky if your samples are not transparent. In that aspect, early zebrafish development is a walk in the park compared to studying non-transparent fly embryos, or even fish in a later stage of development.
But research published in Nature Methods this week comes with a solution. Thanks to Philipp Keller and his colleagues, it’s now possible to take very clear images of non-transparent samples, such as Drosophila embryos, or to monitor zebrafish development much longer – up to three days. This has produced a database of detailed images and movies of Drosophila embryo development.
A few years ago, the group developed a technique called digital scanned laser light sheet fluorescence microscopy (DSLM), in which a laser beam illuminates a slice of the sample, and a detector records fluorescence of just that slice. But that produced a very noisy signal in the presence of many refractive cell membranes – in other words, with non-transparent samples. To solve this problem, they changed the laser beam properties: Instead of a continuous beam of light, the signal was pulsed. By combining multiple pulsed images of the same section, the signal and noise were easier to distinguish, which led to a much clearer image.
How clear exactly? To test the new system (DSLM-SI), Keller monitored zebrafish development up to three days. Compared to studies done with traditional methods, he could see far more detail, including eye and midbrain development. When using DSLM-SI, they were also able to collect very detailed information of cell positions over time in a Drosophila embryo, and combined this information into a dataset with 1.5 nucleus data entries. You can see the resulting dataset, images, and movies on the digital embryo website.
(image via EMBL, courtesy of Philipp Keller and EMBL.)
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