Cyclic nucleotide cycling

I had this idea in my head for a long time before actually committing it to paper. Maybe deep down I was ashamed at such an awful pun. I also couldn’t decide how to draw the molecule on a bike, it didn’t look right freehand. In the end I did it entirely as vector art to match the lefthand panel. On top of this, being bit of a pedant, I wanted to get the structure correct and it took ages to stretch it into shape on the bike whilst retaining the correct relative positions of the atoms and bonds. And having done all that I do find myself wondering who actually cares.

A stinking piece of science cheese

Cyclic nucleotides are responsible for the action of many important drugs from asthma inhalers to Viagra. They are important signalling molecules used to by cells to transform signals from outside the cell into behavioural changes such as making a muscle cell contract or relax. One stunning example is the use of cyclic AMP (cAMP) by slime mould. These ameoba spend most of their time living as single cells. When food is scarce they aggregate into slugs which congregate into a communal fruiting body. This grows up like an antenna and throws out spores over a wide area in an attempt to find a more favourable location. The spores become new single-celled amoeba which happily go about their independent lives until the food runs out again. cAMP is the hunger signal used by slime mould cells to cause them to come together. This has been known for decades and is a classic model of collective cell behaviour relevant to many systems, including the spread of cancer cells. cAMP is colourless and until recently there was no way to directly visualise it. This changed dramatically when scientists genetically engineered the slime mould to contain a protein that makes them glow green when cAMP is not present. When the cells get hungry and start making cAMP it turns off the green fluorescent creating a black dot instead.

Film taken from Hashimura, H., Morimoto, Y.V., Yasui, M. et al. Collective cell migration of Dictyostelium without cAMP oscillations at multicellular stages. Commun Biol 2, 34 (2019). Used under a Creative Commons Attribution 4.0 International License

In the film on the left, the individual amoeba form a lawn of green dots as they have enough food and no cAMP is made. Over time (shown in hr:min:sec in the top left), food becomes scarce and they start to signal to each other with cAMP which turns off their fluorescence as the wave of cAMP sweeps through the colony. The resulting patterns are astounding. There is no CGI trickery here! This is the outcome of millions of individual amoeba talking to each other by producing cAMP!

It seems trivial after such an amazing film but this design is available on a range of cool products from my RedBubble store.

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