Correcting the loss of cell-cycle synchrony in clustering analysis of microarray data using weights.

MOTIVATION

Due to the existence of the loss of synchrony in cell-cycle data sets, standard clustering methods (e.g. k-means), which group open reading frames (ORFs) based on similar expression levels, are deficient unless the temporal pattern of the expression levels of the ORFs is taken into account.

METHODS

We propose to improve the performance of the k-means method by assigning a decreasing weight on its variable level and evaluating the 'weighted k-means' on a yeast cell-cycle data set. Protein complexes from a public website are used as biological benchmarks. To compare the k-means clusters with the structures of the protein complexes, we measure the agreement between these two ways of clustering via the adjusted Rand index.

RESULTS

Our results show the time-decreasing weight function--exp[-(1/2)(t(2)/C(2))]--which we assign to the variable level of k-means, generally increases the agreement between protein complexes and k-means clusters when C is near the length of two cell cycles.