Mary Lyon: a celebration of one of the great female British researchers

Today we say goodbye to one of the great female British researchers: Mary Lyon, who proposed X inactivation, dies aged 89

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Mary Lyon

Today we say goodbye to Mary Lyon, who proposed X inactivation, as she dies aged 89

Mary Lyon, mother of X-inactivation, died on Christmas Day and will be cremated near her home in Oxfordshire today, 16 January 2015.

Mary Lyon proposed the theory of X-inactivation, which is also called Lyonisation after her.  She was an early influential, British female scientist.  Born in 1925, she completed her studies at Cambridge University, at a time when they did not award women degrees. 

Her research has had a fundamental impact on research into human genetics and her accomplishments have been widely recognised by many international honours and prizes, including:  the Royal Medal from the Royal Society, the Wolf Prize for Medicine and the Pearl Meister Greengard Prize (an international award to recognise the accomplishments of outstanding women scientists). She was elected a Foreign Member of the US National Academy of Sciences and in 2014 the UK Genetics Society created the Mary Lyon Medal in her honour. She was a long-term researcher with the Medical Research Council, until (and way beyond!) her retirement, and was commemorated by the MRC, when they named one of their new buildings after her: the Mary Lyon Centre at MRC Harwell, Oxfordshire.

Mary Frances Lyon was born in Norwich, England on May 15 in 1925 to Clifford James Lyon and Louise Frances Lyon (nee Kirby). Mary received a Grammar school education and recalled a set of books on wild flowers, birds and trees that she won in an essay writing competition, which sparked her interest in Biology at a young age.

She went on to read Zoology, Physiology and Biochemistry at Girton College, Cambridge in 1943. At Girton, Mary was named the Sophia Adelaide Turle Scholar (1944) and received the Gertrude Gwendolen Crewdson Prize (1945). During her time at Girton, the fascinating advances in experimental embryology of the 1930s caught Mary’s attention; she was also much influenced by the writings of C. H. Waddington which included his books on Genetics. It seemed to her that genes must underlie all embryological development. This was a relatively new idea at the time, Genetics not even being taught as a degree subject. Mary consequently took a course in genetics by the eminent statistician and theoretical geneticist R.A. Fisher, with who she later started a PhD. For her PhD, Mary decided to study a balance defect in one of the mutants in Fisher’s lab. She however later moved to Douglas Falconer’s lab in Edinburgh for better facilities to complete her PhD.

After obtaining a PhD, Mary was employed to study the genetic hazards of radiation by means of mutagenesis experiments with mice in a group led by T. C. Carter in Edinburgh. The work was funded by an MRC funded grant obtained by Waddington, the head of Genetics department. Carter’s group eventually moved to MRC Radiobiology unit at Harwell, in Oxfordshire where Mary remained for the rest of her career.

Many discoveries coming from Mary’s career were offshoots of the study of these radiation induced mutations in mice; often being investigated in her spare time. X-linked mutant genes, for example, gave mottled or dappled coats in heterozygous animals. Mary worked out that the colour patches could be produced by the action of one of the other X-chromosome in different cells, and proposed the idea of inactivation of one of the two X-chromosomes, which she later extended to all mammals. Mary’s extensive work on the t-complex, a genetic peculiarity found in wildtype mice, also came out of work on radiation.

Mary also had major contributions to understanding environmental mutagenesis. Her work on effects of low dose radiation on female germ-cells mutation in mammals indicated that only a fraction of mutation is due to low dose environmental radiation.

In 1962, Mary took over as head of the Genetics section of the Radiobiology unit at Harwell. Here she broadened the expertise of the unit by introducing Cytogenetics, work on Biochemical genetic markers and early pre-and post-implantation mouse embryo manipulation. Mouse embryo banking started at MRC Harwell under Mary’s leadership, following collaboration with David Whittingham’s laboratory in Cambridge. Today this has taken the form of FESA (Frozen Embryo and Sperm Archive) the sole public UK archiving and distribution centre for mouse strains.

In 1986, Mary officially retired as the head of the Genetics Division, but continued to play an active role in the science of the unit for a very long time after.


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