A month ago, Adrian Lee, Carina Dennis and Philip Campbell published their guide for mentors in Nature. This guide was written following last year Nature awards for creative mentoring in science which had a focus on Australasia. Although this material could be interesting for would-be and already established mentors, it could also be very interesting for would-be PhD students. Very often, the choice of would-be PhD students is made only on the future PhD topic. Although it has to be an important part of the decision process, my advice would be to get some information on the way the future mentor behaves with his/her students. This guide shows it’s also very important for your future career …

Since my Ph.D. is related to memory consolidation, I was interested in a strange idea from Francis Crick. He asked the question of long-term storage of the memory trace ¹. How is this memory trace stored in our brain? And, more importantly, how is it protected against molecular turnover? In his view, Crick suggested three hypothesis:

1. Memory could be encoded in alterations of some part of the cell DNA. This will imply that each neuron synapse would be represented by a part of the neuron DNA since the actual paradigm states that memory is encoded in the strength of individual synapse. This first hypothesis seems unlikely.
2. Memory could otherwise be stored in a local piece of DNA or RNA, at the synapse (a bit like the mitochondrion has its own DNA). This piece would be immune to the molecular turnover. Although more logical, this hypothesis seems unlikely too.
3. Finally, Crick’s last hypothesis states that molecules at the synapse level would interact in such a way they could be replaced by new ones, one at a time, without altering the general status (strength). The figure below shows a working example of this hypothesis …

In this figure, two monomers (squares) forms a hypothetical protein
highly involved in a memory process at the synapse level. Each monomer can be in two states: active (plus sign) or inactive (minus sign). Activation of the monomer could be done by phosphorylation (in this example ; any other modification could be applied here). The hypothetical protein can either be active (plus plus) or inactive. The key point in Crick’s hypothesis is an enzyme which will phosphorylate a monomer if the protein is in state (plus minus), giving an active (plus plus) protein, but not if it is in state (minus minus). This will counteract the molecular turnover which transform an active (plus plus) protein into an inactive (plus minus) one.

Of course, Crick’s hypothesis can be extended to proteins that are trimers, tetramers, … other process than phosphorylation could be used (methylation, glycosylation, …) and more conditions could also be added (anchoring, maturity, …).

What do you think of this hypothesis?

¹ Crick F. “Neurobiology: Memory and molecular turnover” in Nature 312:101 (1984) – read the PDF

Hi!

Since it’s my first post on the Nature Network blog (thanks Matt ) I’ll introduce myself and what I’ll do with this blog …

I’m a Ph.D. student at the University of Liege (Belgium). I was working at the Cyclotron Research Center and the Center for Cellular and Molecular Neurobiology . Now, I’m writing my thesis while waiting for some last results from the mass spectrometry facility.

During my Ph.D. I developed a lot of techniques in my lab in order to look for proteins involved in memory consolidation. We didn’t get exactly the expected results but we still got nice results.

With this blog, I’m planning to share with you some interesting readings I had in the field of neurosciences. I hope you’ll enjoy it and maybe we’ll have interesting discussions about some topics. So, feel free to add your comments! :-)