Centrosomes and Spindle Pole Bodies

From The Mitotic Spindle

The conference we went to last week took place in Heidelberg. We arrived on Friday, at 2:55, and the first talk was at 3! Typically we would go for breakfast around 7:30 AM, start talks at 9 that continued until 1:00 ( with one half hour break). Eat lunch for an hour. Then there was a poster session that went until 5:30 -6:00. We then had another session of talks until 8:00, when we had dinner. We were usually back in the room by 10:00. I should say that while eating and during the breaks, one never stops talking about science, on the talks that were just presented, or sharing our science. So these things can be a bit tiring. The meeting lasted until Tuesday lunch.

I must say that of all the meetings I have ever gone to, I, and for that matter everyone I talked to, had never seen a group of participants that stayed until the very last talk. People almost always leave early, for one reason or another. Not here, there was a palatable enthusiasm for the research.

So centrosomes, what are they, and what are they used for. There most well studied role is in cell division. We all know that when a cell divides it makes a copy of its DNA, or genome. The DNA is in pieces, or chromosomes. One copy of a chromosome goes to one daughter cell, the other copy to the other.

So imagine the chromosomes are like fish. When the cell divides it makes a copy of each fish, and these copies hold fins. They are like sisters who can not be separated. Now here come the centrosomes into play. Centrosomes are like two fishing piers at either end of the cell. Indeed, one might say, at two opposite poles of the cell. The piers are platforms that help organize all the fishermen trying to catch one of the fish. But of course,the fishing would not be any fun if they snagged one and there was no struggle. The cell is designed to make sure that for each pair of sister fish, one fisherman from one pier gets one of them, and another fisherman on the other pier gets the sister duplicated fish. This sets up a certain amount of tension between the two fisherman, as they each try to reel in one of the two fish that are holding each other's fins. The key moment is when all the fish are on hook, and all the fisherman are stressed. Again, they are stressed because the fish comes in pairs, and the pairs are headed to opposite piers. Well, when they are hooked and every fisherman is feeling the stress, a signal goes out, and all the fish let go. The fisherman then reel their catch in to the pier. And the cell divides down the middle between the two piers.

Well, like I said, the piers are my analogy for the centrosome. The fishing lines, well in the cell those would be microtubules. The hook, or the connection between the microtubule and the DNA, that is called the kinetochore. Now all these pieces have to work together, otherwise the daughter cells do not get all the DNA they need, or one gets too much.

So we do not know how cells make the lines. The lines start at the pier, ie. the microtubules start at the centrosome, but how they create themselves is a bit of a mystery. We also do not understand how the hook, or kinetochore works. Like any good mystery, the first step is to identify all the suspects. By now we pretty much know most of the components of these structures. But we do not know how these components fit together and work.

If you are a fan of the game Clue, at some point in the game you might know that the murderer is Mr. Mustard, and the murder took place in the Library, but you do not know the weapon. We are missing the weapon, but we feel close to solving one of the big mysteries of life. So kinetochores and centrosomes are what Trish and I work on.

Enough for tonight. Maybe tomorrow we will discuss centrioles, basal bodies, and our ancient motile ancestor. Because centrosomes probably started out as a structure that organized the microtubules in flagella, or cilia. And there was a lot of research presented on this fast growing field of research.