Immunofluorescent images of formaldehyde-fixed cell lines are shown. Three different organelle markers are displayed as different channels in the multicolor images - nucleus stained in blue, microtubules in red and ER in yellow. The various cell structures that are demonstrated are always shown in the green channel using an antibody found in the Human Protein Atlas. The antibody id is linked to the corresponding Cell Atlas protein page. By using the "toggle channels"-buttons, the different channels can be turned on and off. Most cell structures can be highlighted in the cell illustration by hovering over them with the exception of the aggresome. Cytoplasmic bodies are highlighted as cytosol; cytokinetic bridge, midbody, midbody ring and mitotic spindle are highlighted as microtubules, cell junctions are highlighted as plasma membrane and nucleus is highlighted as nucleoplasm.
Staining of microtubule-organizing center in human cell line A-431 (HPA034964)
Scale bar represents 10µm
Microtubule organizing center
The microtubule-organizing center (MTOC) is located close to the nucleus and consists of the two centrioles together with the pericentriolar matrix around it. This matrix is responsible for the minus end formation of the microtubule filaments
The centrosome is the starting point of microtubule growth. It consists of a centrosome matrix enclosing two centrioles. The major role of the centrosome is to regulate the intracellular organization of the microtubules, which is essential for cell division. After replication of the DNA, the (duplicated) centrosomes move to opposite sides of the nucleus to form the two poles of the mitotic spindle that separates the chromosomes. In motile cells, one of the centrioles serves as the basal body of cilia and flagella during all cell cycle stages except mitosis.
The MTOC always overlaps with the center of the microtubules, making it easy to find. Antibodies that very specifically stain the two centrioles as well as a single spot staining at the origin of microtubules are annotated as centrosome.
If the staining is larger and less distinct but still overlapping with the center of the microtubules, it is annotated as MTOC. MTOC stainings can show both vesicle-like and granular characteristics. Unlike the centrosome the staining of MTOC varies more between different cell lines making them more difficult to identify than centrosomes.