Unique membrane morphology of cellular organelles
Organelles, a crucial cellular compartment in eukaryotic cells, have a complex morphology, which is important for versatile functionality. Most organelles are made of distinct sub-compartments exhibiting specific shapes that are difficult to visualise using currently available imaging modes. The goal of the EU-funded FLUOMORPH (Fluorescent biosensors of organelle morphology to study the nuclear envelope dynamics during cell division) proposal was to develop a method to distinguish organelle sub-structures in live cells using a simple bi-dimensional confocal imaging setup. Fluorescent probes for organelle morphology were designed based on the striking membrane-sensing properties of a family of amphipathic helices called ALPS motifs. To establish the usefulness of these tools, researchers studied the dynamics of the nuclear envelope (NE) and the endoplasmic reticulum (ER) during mitosis. Features of the sequence of ALPS motifs that are critical for their specificity were investigated. Scientists found that while the sequence of the backbone surrounding the ALPS motif can be changed, their structural context is important for the sensitivity to curvature. The changes occurring in ER morphology during cell division have been studied using the probe that stains ER tubules specifically. Based on this study, researchers designed a green fluorescent probe specific for ER tubules. They also created ER- and NE- specific constructs, available as red or green fluorescent proteins. The designed probes enabled the visualisation of ER tubules and ER cisternae at the decondensing chromatin surface during post-mitotic NE assembly. Visualisation of the fine structure of organelles is essential for understanding their associated functions. Applications of this new technology extend beyond biomedicine to many areas including agriculture and animal husbandry.
