In a first segmentation, we detect the nuclei, while in the second pass we will segment the holes (nucleoli). can be informative to study the nucleoli.Īvoid the detection of wrong spots. The intensity, size, shape, number of nucleoli per nucleus, etc. Since we are interested in segmenting the nucleoli, you may wonder why we need to segment nuclei first. These matches are relevant for a meaningful interpretation of the features. It is important to keep in mind that, for CellProfiler, our plateName will be called field1, imageID will be field2, cropX will be field3, etc. The pattern to extract our metadata from the file name properly is, therefore: field1_field2_field3_field4_field5_field6. We have a total of 6 metadata values encoded in the name of the file, separated by _. In our case, the upper-left corner (X, Y) and the width and height from there. These fields indicate to which plate the image belongs, what is the identifier of the image in the IDR, and the 4 cropping parameters selected. The images downloaded from the IDR are named following the pattern: plateName_imageID_cropX_cropY_cropWidth_cropHeight. You will also learn how to extract and export features at three different levels: image, nucleus, nucleolus. In this tutorial, you will learn how to create a workflow that downloads a selection of images from the IDR, and uses CellProfiler to segment the nuclei and nucleoli. Figure 2: High-level view of the workflow 2): identification of the nuclei, nucleoli and background, together with the feature extraction,ģ) CellProfiler tool to actually run the pipeline. To fully emulate the behaviour of the standalone CellProfiler in Galaxy, each image analysis workflow needs to have three parts:ġ) StartingModules tool to initialise the pipeline,Ģ) tools performing the analysis ( Fig. Many of these modules are now also available as tools in Galaxy. CellProfiler normally comes as a desktop application in which users can compose image analysis workflows from a series of modules. To process and analyse the images, we will use CellProfiler ( “ CellProfiler 3.0: Next-generation image processing for biology” 2018), a popular image analysis software. The images and associated metadata will be retrieved from the Image Data Resource (IDR), a repository that collects image datasets of tissues and cells. In this tutorial, we will analyse DNA channel images of publicly available RNAi screens to extract numerical descriptors (i.e. Figure 1: DNA channel from the screen described in “ Integration of biological data by kernels on graph nodes allows prediction of new genes involved in mitotic chromosome condensation” 2014. In particular, regardless of the targeted biological process, many screens include a DNA label and therefore can also reveal the effect of gene knock-downs on nucleoli. Re-using published screens image data can then be a cost-effective alternative to performing new experiments. While screens typically focus on one biological process of interest, the molecular markers used can also inform on other processes. Phenotypes caused by reduced gene function are widely used to elucidate gene function and image-based RNA interference (RNAi) screens are routinely used to find and characterize genes involved in a particular biological process. In DNA staining of cells, nucleoli can be identified as the absence of DNA in nuclei ( Fig. The nucleolus is a prominent structure of the nucleus of eukaryotic cells and is involved in ribosome biogenesis and cell cycle regulation.
0 Comments
Leave a Reply. |