Today was my last day doing at-the-bench experiments at Harvard. On Saturday I will drive away from Boston. Wow!! I am ready for the next step of my transition journey, but I have been thinking about what I have appreciated about the experiments I have done over the past years. The experiment that I did twice this week, and that I have done many times over the last four years, is injecting frog embryos with tiny droplets. These droplets contain reagents that specifically disrupt embryonic development. I am not sure what my future holds, and I am trying to learn to never say never, but I think it is quite likely that I will never do this type of experiment again. Here is my goodbye reflection on what I will miss.
The beauty of dividing embryos.
When I arrived at graduate school, I had only ever worked with bacteria and yeast, both single-cell organisms. I had never taken a Developmental Biology or Anatomy/Physiology class, or thought at all about research using animals. For my first research experience at Harvard, I worked with the roundworm C. elegans, and though I didn’t end up joining that lab, I quickly realized that I wanted to use an animal model system for my PhD research. That system ended up being the Xenopus laevis embryo.
To inject embryos, I look at them through a dissecting microscope. I inject the embryos right after the first cleavage has occurred. Thirty minutes later there will be a second orthogonal cleavage resulting in four cells. The embryos are beautiful. I can’t begin to count how many times I have watched these cleavages happen, and every time I think to myself: “Wow! I am so lucky!” And in addition to the aesthetic beauty, there is the robustness - when healthy eggs have been correctly fertilized, close to 95% of hundreds of embryos and will cleave with this pattern. Regardless of whatever else was happening in my life, the embryos divided, and their beauty was accessible to me.
The performance thrill of injecting embryos.
Injecting embryos (1.3 mm in diameter) is not intellectually challenging, but it requires skill, experience, and performance. The skill is to correctly break finely pulled glass needles to the correct tip width. Then, by adjusting the air pressure and injection time the size of injected droplets can be calibrated. With decent fine motor skills and experience, this is quite doable, but the fun part is the performance. There is a 25-minute window when the two-cell embryos can be injected before the next division occurs. A new needle has to be calibrated and filled every time something different is injected. And this needs to be done such that there is time to inject lots of embryos, but it can’t be done more than ten minutes before the first cleavage event. For a typical experiment, there will be four to six different solutions that are injected. Every time I correctly calibrate a needle with the right timing and inject embryos, I get the thrill of a win.
Working with Christine.
I spent A LOT of my PhD working alone - not just doing experiments by myself or sitting at my computer analyzing data by myself - but also being the only person actively thinking about a project. However, over the last two years the experimental project I have been working on has been a close collaboration with Christine. And we don’t just think about the project together, we actually do the experiments together. We have done these embryo injection experiments many many times, and we have our routine of exactly who does what. In addition, we get to spend the down moments between the action talking to each other about science (or not science). In the past, it was always a big relief to see her when showing up in lab early on a weekend morning, and more recently, while we have been housemates, it’s much more fun walking into lab when it’s the two of us. We will still be friends, and we have writing work to do together on our manuscript revisions, but the physical teamwork and abundant casual quiet moments are ending.