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Department of Mathematical Sciences

Seminar Archives

On this page you can find information about seminars in this and previous academic years, where available on the database.

Biomathematics Seminar: Dissecting quantitative epigenetic silencing through mathematical modelling and experiments

Presented by Martin Howard, John Innes Centre, UK

29 November 2011 14:00 in CM105 (Mathematical Sciences)

Vernalization, the perception and memory of winter in plants,
is a classic epigenetic process that involves epigenetic silencing of
the floral repressor gene FLC. The slow dynamics of vernalization,
taking place over weeks in the cold, generate a level of stable
silencing of FLC in the subsequent warm that depends quantitatively on
the length of the prior cold. The silencing is mediated by the addition
of covalent modifications to histones around which DNA is wrapped, in
this case trimethylation of histone 3 lysine 27 (H3K27me3). Using
mathematical modelling, chromatin immunoprecipitation and an FLC:GUS
reporter assay, we have shown [1] that the quantitative nature of
vernalization is generated by H3K27me3-mediated FLC silencing in the
warm in a subpopulation of cells whose number depends on the length of
the prior cold. During the cold, H3K27me3 levels progressively increase
at a tightly localized nucleation region within FLC. At the end of the
cold, numerical simulations predict that such a nucleation region is
capable of switching the bistable epigenetic state of an individual
locus, with the probability of overall FLC coverage by silencing
H3K27me3 marks depending on the length of cold exposure. Thus, the model
predicts a bistable pattern of FLC gene expression in individual cells,
a prediction we verified using the FLC:GUS reporter system.

[1] Angel, Song, Dean, Howard: A Polycomb-based switch underlying
quantitative epigenetic memory
Nature 476 105-108 (2011)

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