标题：Mélanges gaussiens bidimensionnels pour la comparaison de deux échantillons de chromatine immunoprécipitée. Caroline Bérard, Marie-Laure Martin-Magniette, Alexandra To, François Roudier, Vincent Colot, Stéphane Robin.
摘要：Chromatin immunoprecipitation (ChIP) enables to investigate interactions
between proteins and DNA and also various chromatin states. ChIP-chip is
a well-established procedure combining chromatin immunoprecipitation with DNA
microarrays, which allows a study of the whole genome. We are interested in the
analyze of the differences between two immunoprecipitated DNA samples. From a
biological point of view, we expect to distinguish four different groups : a group of
non-immunoprecipited DNA, a group of immunoprecipited DNA in both samples,
and then two groups in which DNA is differently immunoprecipited. We propose to
model these data with a mixture of two-dimensional Gaussians with four components.
Biological knowledges are included as constraints on the variance matrices.
The parameters are estimated by the EM algorithm. This method is applied to NimbleGen
data in order to study the histone methylation difference between the wild
ecotype of the model plant Arabidopsis thaliana and a mutant.
关键词：Gaussian mixture, eigenvalue decomposition, EM algorithm,
ChIP-chip.
