Today, I spent my afternoon making transgenic worms.
On a very basic level, here’s what that means…
I start out with a bunch of plain old C. elegans, which look like this:
I pick worms that are young adults, and I shoot up their gonads with DNA that encodes a glowing protein like GFP. The end result, if it all works out, is little baby glowing worms in a few days. They’ll grow up to look something like this:
If everything works really well, THOSE worms will have glowing babies, and then I can do experiments.
This is really, really cool. Transgenic organisms are nifty in a “mwha-ha-ha-ha, I’m playing god,” kind of way, and they also are incredibly useful research tools.
But that’s not what I want to tell you about at the moment. Instead, let’s talk for a minute about the mechanics of actually making this happen.
For starters… these things are tiny. As in, an adult worm is roughly 1mm long. So manipulating them without killing them is hard enough in general, but sticking holes in them, squirting in DNA, and then having them live… it’s quite the feat. Here is roughly how it goes:
- Make microinjection needles by precisely heating and pulling apart glass capillary tubes (thankfully, there is a machine that I use to help me do this).
- Fill microinjection needles with ‘microinjection mix’… aka, DNA in water.
- Load needle onto microinjector and precisely break end of needle under the microscope so that the hole is the ‘right size’ for injecting.
- Take worm off agar plate where it is happily roaming around, eating bacteria, and place it in a tiny drop of microinjection oil on a glass slide.
- Put slide on microscope, find worm and line up needle. Get everything in focus, stab + squirt.
- Take slide off microscope, squirt worm with buffer, suck up worm and deposit back on fresh agar plate.
- Repeat from step 4 until you screw something up. Then fix what you broke, and start again.
Now, that sounds relatively straightforward, but literally every step is delicate and fiddly and arrrrrrgh. The microinjection needles are tiny and delicate, and easy to break just in handling/transport. When you fill them, you are filling them with less than a microliter of liquid (a tiny, tiny fraction of what you would usually think of as a ‘drop’), and you end up with microscopic air bubbles that MUST be gotten rid of before injecting. Loading the needle is another chance to drop/break it, and breaking the perfect size hole is an art. When you put the worm on the slide, you have to smush them down a bit so they stop moving, but not actually smash them. When injecting, you have to get precisely in the gonad of the worm (where the eggs are formed), and messing this up leaves you at best with an unsuccessful injection, and at worst with a dead worm skewered on your needle. And even if you succeed in everything up to that point, and have a perfectly injected, healthy wiggly worm… it’s still possible to lose or kill it just trying to get it off of the slide and back onto a plate. And even after that, sometimes worms that appear to have survived the procedure never recover, and others that recover never produce transgenic progeny.
As fiddly as this whole mess is, all of it can be learned. I now know the precise amount of force with which to flick a glass capillary needle in order to move air bubbles without breaking the needle or flinging it across the room. About nine times out of ten, I can poke the tip of the needle into a broken piece of glass just right so that I get a workable hole through which to inject. I rarely outright smash or skewer my worms, although I always kill a few, as does everyone else who does this–which is why we try to end up with at least ten “wigglers” for each set of injections, in hope that at least one of them will give us glowy babies.
And actually, once I’m all set up and get “in the zone”, so to speak, I actually enjoy injecting. I’m in a quiet microscope room by myself, and can work for hours without being interrupted. I work while listening to music or podcasts, and after awhile I reach this place of a kind of… intense calm. I’m incredibly focused, but relaxed. At its best, it’s kind of meditative and lovely.
But to get to this point, it took me hours and hours of practice. Many of those hours were endlessly frustrating, leaving me cursing worms and science and microscopes and my stupid clumsy fingers. And when I finally got my first transgenic lines, I was so goddamn proud.
And I should be proud. Microinjection is a hard-won skill. Hard-won… but completely useless outside my field.
This is common in science. We spend hours upon hours–sometimes years–perfecting skills that many of us will never use after our current project ends, or after our PhD. When I’m out on the job market some day, the odds that I’ll encounter anyone who gives a damn about the precision with which I can break a microinjection needle are pretty slim.
I’m not really bitching. This is the nature of the beast. And one could argue that while no one will give a fuck about my worm-injecting skills unless I spend the rest of my career in worm labs, the process of learning to inject has taught me more general, transferrable skills… like absurd determination and patience.
But man, sometimes as I sit there, gently flicking a needle, waiting for the air bubbles to rise out of the tip, I think…god, how many hours of my life have gone to learning this, when in the grand scheme of things, no one is going to care.
So yea… this is what happens when I spend a whole afternoon shut in a room with our microinjection setup and my own thoughts. Anyhow, do you have any hard-won but useless-outside-a-very-narrow-field skills? If so, tell me about them in the comments!