Supplemental information PreMosa : Extracting 2 D surfaces from 3 D microscopy mosaics

In epithelial tissues, some subcellular structures that localizes along a 2D manifold do not yield equally distributed and relatively dense signals. In the case of a sparse distribution, the extraction of the correct signal becomes very challenging. Nevertheless, to still enable an analysis of the signals, one typically labels a second structure, which is spatially close to the signal of interest and yields the required signal density. Using the introduced projection method, it is now possible to automatically extract and project the sparse structures of interest given the estimated surface of the second structure. To do this, the height map presenting the estimated surface is included as initial height map and optimized using only the second selection step, which fits each z-section to the location of the sparse, but sharp signals of interest. If an offset in z-direction between the two channels is priorly known, it can be also taken into consideration. The extension for multi-channel images allows one to project challenging 2D surfaces if a more significant surface can be identified nearby.