Abstract
BackgroundThe ability to detect nuclei in embryos is essential for studying the development of multicellular organisms. A system of automated nuclear detection has already been tested on a set of four-dimensional (4D) Nomarski differential interference contrast (DIC) microscope images of Caenorhabditis elegans embryos. However, the system needed laborious hand-tuning of its parameters every time a new image set was used. It could not detect nuclei in the process of cell division, and could detect nuclei only from the two- to eight-cell stages.ResultsWe developed a system that automates the detection of nuclei in a set of 4D DIC microscope images of C. elegans embryos. Local image entropy is used to produce regions of the images that have the image texture of the nucleus. From these regions, those that actually detect nuclei are manually selected at the first and last time points of the image set, and an object-tracking algorithm then selects regions that detect nuclei in between the first and last time points. The use of local image entropy makes the system applicable to multiple image sets without the need to change its parameter values. The use of an object-tracking algorithm enables the system to detect nuclei in the process of cell division. The system detected nuclei with high sensitivity and specificity from the one- to 24-cell stages.ConclusionA combination of local image entropy and an object-tracking algorithm enabled highly objective and productive detection of nuclei in a set of 4D DIC microscope images of C. elegans embryos. The system will facilitate genomic and computational analyses of C. elegans embryos.
Highlights
The ability to detect nuclei in embryos is essential for studying the development of multicellular organisms
Appearance of nuclei in images obtained by the 4D differential interference contrast (DIC) microscope system The appearance of the nuclei of C. elegans embryos in 4D DIC microscope images (Figure 1A, B) varies among different focus levels and different developmental stages
Digital images of a developing embryo were recorded in multiple focal planes and a set of multifocal images was recorded with a fixed time interval, α. (B) Example of 4D DIC microscope images of a C. elegans embryo
Summary
The ability to detect nuclei in embryos is essential for studying the development of multicellular organisms. A fertilized egg – a single cell – develops into a multicellular organism through many spatially and temporally dynamic cellular activities, including cell division, cell migration, cell differentiation, cell fusion, and cell death. Often, these dynamic cellular activities are described in terms of the positions of the nuclei, and the roles and mechanisms of those cellular activities are studied using these descriptions of cellular activities because the nucleus is generally positioned at the center of a cell (page number not for citation purposes). Detection of the nucleus in microscope images is essential for studying the development of multicellular organisms. High objectivity of measurements is strongly expected in bioinformatics and computational biology. Organisms have thousands of genes [4,5], and systematic study of the functions of all of these genes – a typical strategy in genomics – needs thousands of measurements [6]
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