• Question: During Mitosis/Meiosis what keeps the centrioles at opposite sides of the cell?

    Asked by beccabas to Anouk, Chris, Judith, Leisha, Seyyed on 19 Jun 2012.
    • Photo: Judith Sleeman

      Judith Sleeman answered on 19 Jun 2012:

      That is a really excellent question (again!)

      When a cell is not in mitosis (so I’m answering your question backwards, sorry!), the two centrioles are held together by a number of linker proteins: they bind to both and keep them tightly together. As the cell goes into mitosis and needs to form a mitotic spindle, another set of proteins are activated and they alter the proteins that are holding the centrioles together (a type of protein modification called phosphorylation is involved, as with many other regulated events in cell biology!). This allows the centrioles to separate. Then, each centriole moves along the microtubules in the cell (the fibres that make up the spindle) using motor proteins that sort of ‘walk’ them along the fibres. So one ends up at each end of the cell.

      What keeps them there, I couldn’t find out. This is the closest I could get from a review in the Journal of Cell Biology published this April: “Complete spatial separation of the two disengaged centrioles may depend on MT (microtubule)-mediated forces to physically and mechanically push centrioles apart”. So, I think no-one knows for sure. Yet…

    • Photo: Chris Kettle

      Chris Kettle answered on 21 Jun 2012:

      Hi beccabas. Chromosomes attach themselves to the spindle via their centromeres and structures called kinetochores (roughly translates means centres of movement). Chromosomes allign along the equator of a cell at a point in mitosis/meiosis called metaphase. By this point all of the cellular machinery required to move the chromosomes has been assembled, centrioles, spindle etc. the centrioles are at opposite poles of the cell and pull the half of the chromosomes to each pole so that the number of chromosomes in each daughter cell identical.

      The spindle fibres are made of microtubulin which is gradually shortened and that’s how the chromosomes are pulled. As Judith mentioned, not much is known about what actually keeps the centrioles in their place but it is very important that they do stay in place- if they didn’t cell division would break down and we would never be a blue to grow or repair ourselves!

      My best guess would be a group of anchoring proteins that restrict the movement of the centrioles but this is a guess and not fact 🙂 hope thtbhelps

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