Defining an epigenetic code

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The nucleosome surface is decorated with an array of enzyme-catalysed modifications on histone tails. These modifications have well-defined roles in a variety of ongoing chromatin functions, often by acting as receptors for non-histone proteins, but their longer-term effects are less clear. Here, an attempt is made to define how histone modifications operate as part of a predictive and heritable epigenetic code that specifies patterns of gene expression through differentiation and development.

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Figure 1: Histone modifications can generate both short-term and long-term outcomes.
Figure 2: A hypothetical illustration of how an epigenetic code may work in the pre-implantation embryo.

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Acknowledgements

I am grateful to M. Barbieri for drawing my attention to the world of semiotics, and to A. Ferguson-Smith and colleagues in the Chromatin and Gene Expression Group for their thoughts, criticisms and insights.

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