Embryonic development: How do limbs develop from cells?
New microscopy software enables precise monitoring of cells
During the development of a multicell organism, a single cell produces a range of different cell types which in turn form various tissues and organs. For over a century, biologists have been attempting to understand the biogenesis (also known as cell fate) of the different structures in developing organisms. For instance, which cells produce eyes or limbs? How does the behaviour of these developing cells change in order to realise the form and function of the respective organ?
Until now, it has been exceedingly difficult to answer these kinds of questions since directly observing developing embryos at the cellular level poses a considerable challenge. Following a new approach, a multinational and interdisciplinary team of scientists from the Humboldt University of Berlin, the Max-Planck Institute for Molecular Cell Biology and Genetics (Dresden), the HHMI Janelia Research Campus (USA), the Max-Delbrück Centre for Molecular Medicine (Berlin) and the Pasteur Institute (France) is investigating the dynamics and behaviour of cells during limb development.
In this connection, the research team is taking a closer look at the development of the marine crustacean Parhyale hawaiensis. This creature has developed an array of specialised limbs along the length of its body – resembling a living Swiss army knife. Using state-of-the-art light sheet fluorescence microscopy, the researchers were able to record the entire embryonic development of embryos with fluorescent cell nuclei. This procedure involved the embryos being observed from different perspectives in a high spatial and temporal resolution.
Cell monitoring can provide insights into deformities
Having collecting these complex and multidimensional microscopic images, the researchers faced the challenge of extracting the relevant biological information from these huge data sets. To this end, they developed a special software program called Massive Multi-View Tracker (MaMuT), which is freely available as a FIJI plug-in. This combination of microscopy and software allowed the scientists to examine all the cells of a leg during development over the course of several days.
They were thus able to discover morphogenetic behavioural patterns of the cells which contribute to the cellular organisation and growth of a leg. In the future, this new method of examining the development of multicell organisms will help to identify the cellular and molecular mechanisms that determine the fate of cells during the development of an organism. It will also undoubtedly prove useful in explaining the causes of deformities during development.
The developmental sequence of Parhyale hawaiensis captured
using alight screen fluorescence microscope. This concerns 3D
reconstructions of an embryo from a lateral view and the head
on the left side. The areas highlighted in colourshow how legs differ
on the basis of just a small number of cells.
Dr Carsten Wolff
Institute for Biology
Tel.: 030 2093-6284