Tuesday, September 29, 2009

What I see in the microscope

Here's something I do a lot of at work: injecting sea urchin eggs. Someone in the lab set up a video camera through the microscope to take this video of injections. You can see some eggs in sea water that have been stuck to the petri dish in a neat row. The eggs are about forty microns across, just barely large enough to see them with the naked eye as tiny specks in the plate. When an egg is fertilized with a sperm, it very quickly (within one minute) raises a membrane that prevents any other sperm from getting near. (A human egg doesn't do that, but it has other mechanisms to ensure that it's fertilized by only one sperm.) You can see in the video that all these eggs are fertilized except one at the very top of the frame. In about an hour and a half the fertilized eggs will all divide into two cells, and then there'll be no stopping them. In twenty-four hours they'll be cute little embryos, hatched from their membranes and swimming around the dish.

But first the little suckers get injected! In this video a microscopic needle lowers into focus. The person doing in the injecting has various fine controls that move the needle around. He rests the needle against an egg and then hits a foot pedal that forces a tiny amount of air into the needle, forcing an equally tiny amount of injection solution into the egg. You can see the light gray puff inside the egg where dense egg cytoplasm is suddenly displaced by less dense injection solution. There's no sound in the video, but in real life each injection makes a satisfying click-whoosh sound, and the whole thing is vaguely like playing a video game. I enjoy it. :)

What do we inject? Lots of stuff, but the most popular is a big piece of DNA called a BAC. The BAC usually contains a sea urchin gene of interest, and it also contains a gene from a jellyfish for green fluorescent protein (GFP). If all goes well, the injected DNA will use the sea urchin egg's cellular machinery to make a hybrid protein-- the protein from the gene of interest, and GFP that glows green under UV light. Then when the embryo's developed a bit, I can slap it on a microscope slide, turn off the lights in the room, shine a UV light through the slide, and see where the embryo is glowing. That tells me where the gene of interest is expressed.

That's the simplest experiment; there are also more complicated ways to use injections, but this post is plenty long already. Here's the video. :)


video

9 comments:

JimAroo said...

The Heavens proclaim the Glory of God and so do the fertilized sea urchin eggs.

Warren said...

That is cool. I take it there is some genetic or evolutionary research going on here?

That interesting genetic material... Does it have any similarity to whatever they stuck in to make the new "Glo-Fish" genetically modified aquarium fish they're selling all around the USA these days?

W

Rachel Gray said...

Jim-- whether you use a telescope or a microscope, there's awesome stuff to be found.

Warren, quite right. In our lab we mostly study development (many major discoveries in developmental biology were made first in the sea urchin), and that has plenty of implications for evolution and genetics. GFP is the same stuff that makes the green Glo-Fish glow. There are other similar proteins-- all found naturally in various ocean creatures-- that glow red or yellow or blue, and some of them are used for the other Glo-Fish colors. And I'm pretty sure they produced the original Glo-Fish by injecting them with BACs just like I do, which gets me thinking... selling Glo-Fish as pets is illegal here in California, but if I could just grab some zebrafish eggs and sperm I might be able to get a black market business going. :)

Rachel Ann said...

FASCINATING!!! But you missed one...

Rachel Gray said...

I wasn't actually doing the injecting in this vid; it was somebody else sixteen years ago... *I* never miss. :)

*cough*

Heather said...

Wow, very cool! :-D It's great to see some video to go with the stories I've heard of your job.

Hey, if I bring Chase over one of these days, can you inject him and make him into one of those glowing beagles I saw in the news a while back? ;-)

Rachel Gray said...

I forgot about the glowing beagles! Well, the problem is that with an already-grown animal I'd have to inject each individual cell in his body. But Chase wouldn't mind, right?

Ashley R. said...

ohh wow.. you are so good at injecting them..

We did this technique with drosophila eggs.. needless to say, i wasn't that good at all. I burst about half of the eggs. Def. a technique that requires a fine touch

Rachel Gray said...

Wow, I've never injected drosophila eggs. I think it must be harder than urchin eggs, because you can't burst an urchin egg unless you're really trying hard. The membranes are quite stretchy. It's a pretty forgiving procedure, fortunately. :)