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CRG researchers confirm that a mathematical theory first proposed by Alan Turing in 1952 can explain the formation of fingers

25 Sep 2014

In a paper published recently in Science, researchers from  Multicellular Systems Biology lab at the Centre for Genomic Regulation (CRG) in Barcelona led by ICREA Research Professor James Sharpe, show that BMP and WNT proteins are the so-called “Turing molecules” for creating embryonic fingers. This confirms a fundamental theory first proposed by the founding father of computer science, Alan Turing, back in 1952. BMPs and WNTs interact in a self-organising process, producing a repetitive pattern of gene expression that determines which cells should become fingers. This explains why polydactyly – the development of extra fingers or toes – is relatively common in humans, affecting up to 1 in 500 births.

The approach taken was that of systems biology – combining experimental work with computational modelling. In this way, the two equal-first authors of the paper were able to iterate between the empirical and the theoretical: the lab-work experimental data for the model, and the computer simulations making predictions to be tested back in the lab. 

This result answers a long-standing question in the field, but it has consequences that go beyond the development of fingers. It addresses a more general debate about how the millions of cells in our bodies are able to dynamically arrange themselves into the correct 3D structures, for example in our kidneys, hearts and other organs. It challenges the dominance of an important traditional idea called positional information, proposed by Lewis Wolpert which states that cells know what to do because they all receive information about their “coordinates” in space (a bit like longitude and latitude on a world map). This publication highlights instead that local self-organising mechanisms may be much more important in organogenesis than previously thought.

Arriving at the correct understanding of multicellular organization is essential if we are to develop effective strategies for regenerative medicine, and one day to possibly engineer replacement tissues for various organs. In the shorter term, these results also explain why polydactyly – the development of extra fingers or toes – is such a common birth defect in humans: Turing systems are mathematically known to have slightly lower precision in regulating the number of “stripes” than alternative models.