Talk for the 65th reunion of the Grass Fellowship Program


Dan Johnston, Grass Fellow in 1976



I want to thank the organizers for giving me the honor of speaking to such an august group of scientists. I’m not sure what Felix had in mind for these talks, but I thought I would use my time to relate my experience before, during and following my time as a Grass Fellow in 1976,

So what was my project?

1975PublicationThe idea for my project came from the first paper I ever published. (I naturally assumed that with my first paper being in Science that all my subsequent papers would be in Science—needless to say it didn’t quite work out that way!) I was doing a postdoc in the lab of Giovanni Ayala, who at the time was quite famous for his work on focal epilepsy in cats. I was a staunch invertebrate guy, having done my PhD on Limulus retina and also working on Aplysia as a grad student, so I thought that I could solve the problem of epilepsy by working on Aplysia bursting neurons as a model for bursting in epilepsy—more on that later. I had built my first two electrode voltage clamp and tested the effects of a common anticonvulsant on bursting cells, but I felt I needed to look more directly at calcium currents, the presumed mediator of bursts. I thought that the best way to do this would be to study calcium currents at the presynaptic terminal of the squid giant synapse. Ayala was well connected to the field of epilepsy, as were Albert and Ellen Grass (Albert was the inventor of the first EEG machine), so he knew about the Grass Fellowship program at the MBL and suggested I apply. I had never heard of the Grass Fellowships nor much about the MBL other than as a grad student at Duke I saw two professors, John Moore and Toshio Narahashi move their labs every summer to MBL to work on the squid giant axon.


Grass Fellowship

SquidSGSSo, I applied for a Grass Fellowship to test the effects of Dilantin on calcium currents at the presynaptic terminal of the squid giant synapse. Fortunately for me, the Grass committee accepted my application, so I took off for Woods Hole with my home-built 2-electrode voltage clamp in hand. I barely knew where Woods Hole was, and I certainly knew very little about squid other than the calamari I ate at Italian restaurants

It seemed easy enough, all I had to do was put two electrodes in the large presynaptic terminal, isolate calcium currents, and test the effects of Dilantin (Phenytoin). Oh, to be so young and naive!
When I arrived in Woods Hole I immediately sought out help with the squid experiments. Little did I know that at the time there were two competing groups, fiercely competitive, who were both rushing to be the first to voltage clamp the squid giant terminal and measure presynaptic calcium currents. I guess my idea was a good one, just several years behind everyone else.
When I heard about these two competing groups at the MBL, I was definitely a little worried that no one was going to be willing to teach me the squid synapse prep. This was one of my first important lessons on the competitive nature of science.


The Scoop

The first paper on presynaptic calcium currents was published by the Llinas group at the end of that summer of 1976. The second paper by the Charlton group, which was later joined by George Augustine, another Grass Fellow, was published a few years later.


Milton Charlton

MiltFortunately, Milt Charlton took me under his wing and showed me everything. For example, what size squid to use, how to dissect the synapse, how to choose synapses positioned correctly for proper electrode access, etc, etc. Milt was very generous with his time, and this experience led to a long-term friendship. If it hadn’t been for the expertise of the summer scientists at the MBL, in my case from Milt Charlton, I would have accomplished nothing during my summer fellowship.
Well, by the end of the summer, I did successfully voltage clamp the squid synapse and measure presynaptic calcium currents. I even got a chance to test the effects of Dilantin (which had no effect—we and others showed later that it affects sodium channels).
Overall, the summer was an incredible experience for me. First, I had to put together a rig for doing squid experiments on my own. Second, I learned how to navigate through a rich environment of outstanding scientists at the MBL to find the help I needed. Third, I learned how to interact with an outstanding group of Grass Fellows, which was somewhat intimidating for me. They all seemed so smart and well trained, but in the end I did somehow manage to fit in and form some lasting friendships. Finally, the overall environment at the MBL was simply amazing. We interacted with top scientists who gave special talks to the Grass Fellows every week. There were outstanding seminars, in particular, the Monday neurobiology seminars, which at the time were called the “monday night fights”. And we talked science endlessly among ourselves and among all the other scientists during meals at Swope.
The experience was completely transformative for me. It literally changed my life and career. At the end of the summer, I knew I wanted to come back to Woods Hole and the MBL again to do summer research projects. But my career took a turn away from marine organisms, making it infeasible to work at the MBL. I transitioned from Aplysia to brain slices. This change was motivated by my first NIH grant application, in which I proposed to use Aplysia as a model for epilepsy—it was rejected. One of the reviewers said that until I could show that an Aplysia had a seizure, I would never get funded. I took this criticism to heart and switched to brain slices for studying epilepsy and many other things.

MurineBiologicalLaboratoryMurine Biological Laboratory

Fortunately, around 1988 the MBL opened it’s first vivarium for housing small mammals (rats, mice and rabbits) and became the “Murine Biological Laboratory”. It was a small room above an old building near the current Marine Resources Center. This now provided the opportunity for me to do research at the MBL on rat brain slices.

Another stroke of luck for me was to hook up with John Lisman and Bill Ross in 1989 for a summer of research at the MBL—the first for me since my Grass Fellowship in 1976. I had met John while I was a Grass Fellow. He was transitioning from his work on Limulus photoreceptors to brain slices. Bill Ross, an expert in real time imaging of changes in intracellular Ca with activity, was working with Ann Stuart on barnacle photoreceptors. That summer in 1989 started a more than 10 year collaboration with Bill, John and many others working together each summer at the MBL.


Nechama Ross was also a critical member of the group as was Jay Callaway and David Jaffe.

Also, Hiro Miyazawa. Over the years there were many other important collaborators, including students, postdocs, and other faculty.

This was the fiNaSpikesrst publication from our collaboration. It was a seminal paper at the time and actually preceded the important paper by Stuart and Sakmann that demonstrated back-propagating action potentials into dendrites using patch clamp techniques. For our paper we used calcium and sodium imaging to show that action potentials in the soma propagated into the dendrites and elicited increases in intracellular calcium. All of this work was done during a couple of summers at the MBL. This first paper was followed by many others reporting on experiments done, either entirely or partially, during more than a dozen summers at the MBL. Some of the many collaborators involved in this work, largely reflecting our continuing interest in dendrites, included Jeff Magee, Dax Hoffman, Andreas Frick, Sonia Gasparini, Lise Eliot, Brian Christie, Amiel Rosenkranz, Angel Alonso, Rishi Narayanan, Helmut Koester, Ken Ito, and many others. None of this would have happened without my first experience at the MBL as a Grass Fellow and the many excellent scientists and students I had met there over the years.

Looking back over my career, it is hard for me to imagine where I would be or what I would be doing now if it hadn’t been for that first summer at the MBL as a Grass Fellow. It was clearly a transformative experience for me, and I will be forever grateful for the vision of Ellen and Albert Grass for initiating this fellowship program and for all the many people who have maintained it at the same level of excellence for over 65 years. In looking at the list of former Grass Fellows, Directors, and Associate Directors, it is a veritable list of Who’s Who in neuroscience.

The Grass Foundation through the fellowship program as well as their strong support for the neuroscience-related courses at the MBL, has had an enormous and probably immeasurable impact on the field of neuroscience. My hope is that the Fellowship program as well as the rich environment of summer neuroscientists doing research at the MBL will continue unabated for another 65 years and beyond. Thank you!


(Note: I have no written documentation for some of the specifics in this talk as everything comes from what I remember. I apologize if I am inaccurate on some dates and other particulars in this presentation.)

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