This letter appeared in Nature in 1970:
Diffusion in Embryogenesis
SIR,—As an embryologist who started work during the heyday of "fields" and "gradients", I suppose I ought to be grateful to Dr Francis Crick for allowing me a nostalgic look back at these long-discredited concepts which he has now resurrected—or should I say, canonized—with the double halo of his own reputation and some elegant mathematics (Nature, 225, 420; 1970). There is, however, one point that he appears to overlook: the extreme rarity with which sheer diffusion processes occur in living systems. Twenty years ago my better-informed colleagues told me about active transport and permeases. Ever since then, if materials have diffused in and out of my experimental embryos, I have regarded it as a sign that they are dying or dead. A sheet of frozen-dried tissue, extended between source and sink, might fit Dr Crick's formulae, but-alas-it would not differentiate!
Yours faithfully
ELIZABETH M. DEUCHAR
The Medical School, University of Bristol
Well, Francis Crick couldn’t fail to get that message. Leave it to the real embryologists is the bit between the lines. And indeed Elizabeth Marion Deuchar was a real embryologist in the days before embryology morphed into developmental biology. She was born on 13 February 1927 in Biggleswade, Bedfordshire. After graduating in zoology from Oxford in 1948 she moved to Edinburgh where as a member of staff of the Agricultural Research Council (now BBSRC) at the Animal Breeding Research Organisation she worked with Conrad Hal Waddington FRS (1905-1975) for a PhD. From 1953 to 1966 she was Lecturer and then Reader in Embryology at University College London. She then appears to have taken what turned out to be a very different path. She resigned in order to attend theological college. However, in 1968 she returned to embryology, in the Department of Anatomy at Bristol. She married in 1972 at the then late age of 45 and moved to the University of Exeter. Elizabeth Deuchar died of cancer on 26 January 1979 near Axminster in Devon, aged 52.
The question now is: was she right in challenging Crick? The answer must be no because she seems to have confused movement of substances across cell membranes, where simple diffusion is indeed rare, with movement between cells in the extracellular space or, as shown later, from cell to cell through ‘gap’ junctions. The arguments of whether a simple diffusion gradient, to which cells respond depending on the concentration of a signalling chemical to which they are exposed, is modified by, for example, binding of the substance by cells, continue.
Ruth Bellairs (1926-2021), her former colleague at University College London, who wrote an obituary for the Journal of Embryology and Experimental Morphology thought highly of her:
Elizabeth Deuchar published over 60 scientific papers and three books, but her influence on the subject went far beyond that. Apart from the fact that she was an inspiring teacher to several generations of undergraduates and Ph.D. students, she was one of those dedicated scientists who quietly organise meetings and seminars, sit on committees and give their time unselfishly to help others.
More recently, John Wallingford of the University of Texas at Austin, in his 2022 chapter on the history of Xenopus in research which he kindly sent to me, discussed the spat with Crick and reached the same conclusion as I did. However, he also includes another Deuchar gem:
When a developmental biologist says “in mammals” he probably means “in the mouse”; by “in birds” he almost certainly means “in the chick”. When he generalizes more widely than this about mechanisms of differentiation in “all developing cells” there is a danger that he is referring to work carried out exclusively on Xenopus.
—Elizabeth Deuchar (1972)
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| Elizabeth Marion Deuchar 1927-1979 |
Bellairs R. 1980. Dr Elizabeth Marion Deuchar (1927–1979). Journal of Embryology and Experimental Morphology. 57,1–2.
Deuchar EM. 1970. Diffusion in embryogenesis. Nature 225, 671. 10.1038/225671b0
Kuhn T, Landge AN, Mörsdorf D, Coßmann J, Gerstenecker J, Čapek D, Müller P, Gebhardt JCM. 2022. Single-molecule tracking of Nodal and Lefty in live zebrafish embryos supports hindered diffusion model. Nat Commun 13, 6101 doi 10.1038/s41467-022-33704-z
Wallingford JB. 2022. A quick history of Xenopus. “The humble batrachian”. In, Xenopus. From Basic Biology to Disease Models in the Genomic Era. edited by Abraham Fainsod and Sally A Moody. p1-12. Boca Baton, Florida and Abingdon, Oxford: CRC Press. doi: 10.1201/9781003050230-2
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