After starting life with a single nucleus, the fruit fly (Drosophila melanogaster) embryo divides into many cells through the process of mitotic division and the formation of cell membranes. In normal embryos, the cells move in a very stereotypical way to deform tissue and form functional organs robustly. We have observed an abnormality of these movements within mutated embryos, causing them to produce an excess of essential metabolites, divide faster, and ultimately die. This observation opens an unexplored connection between metabolism and mechanics in developing Drosophila embryos. To describe these aberrant movements, we tracked cells in the nearly oval-shaped embryos to calculate the velocity field. By processing movies from live microscopy and using mathematical tools of dimensionality reduction, we found the major components of the dynamic velocity fields.
In our cover image for the May 19 issue of Biophysical Journal, we show the top five components of the velocity field (left to right) in five mutated embryos. To create the image, we put particles uniformly on the surface of the embryo and traced where they went and where they came from, integrating their position forward and backward in each velocity field. We illustrated the velocity fields by flattening the surface of the oval-shaped embryos in a similar way to how the Earth is flattened on a map. Together, they demonstrate the embryo-scale spirals observed in the mutated embryos. The locations of the spirals are not conserved from embryo to embryo, suggesting their self-organized nature. We colored the traces based on the direction of rotation of the spirals —counterclockwise (green) to irrotational (blue) to clockwise (red). The presence of both clockwise and counterclockwise spirals suggest the rotations are not directionally biased.
To find more works from our lab using experimental and computational tools to understand developmental processes, especially in the oogenesis and embryogenesis of Drosophila, please visit http://shvartsmanlab.com.
- Sayantan Dutta, Nareg J.-V. Djabarayan, Celia M. Smits, Clarence W. Rowley, Stanislav Y. Shvartsman