title: Using GeneReg to construct time delay gene regulatory networks.
abstract: BACKGROUND
  Understanding gene expression and regulation is essential for understanding biological mechanisms. Because gene expression profiling has been widely used in basic biological research, especially in transcription regulation studies, we have developed GeneReg, an easy-to-use R package, to construct gene regulatory networks from time course gene expression profiling data; More importantly, this package can provide information about time delays between expression change in a regulator and that of its target genes.
  
  
  RESULTS
  The R package GeneReg is based on time delay linear regression, which can generate a model of the expression levels of regulators at a given time point against the expression levels of their target genes at a later time point. There are two parameters in the model, time delay and regulation coefficient. Time delay is the time lag during which expression change of the regulator is transmitted to change in target gene expression. Regulation coefficient expresses the regulation effect: a positive regulation coefficient indicates activation and negative indicates repression. GeneReg was implemented on a real Saccharomyces cerevisiae cell cycle dataset; more than thirty percent of the modeled regulations, based entirely on gene expression files, were found to be consistent with previous discoveries from known databases.
  
  
  CONCLUSIONS
  GeneReg is an easy-to-use, simple, fast R package for gene regulatory network construction from short time course gene expression data. It may be applied to study time-related biological processes such as cell cycle, cell differentiation, or causal inference.
authors.affiliation: Key Laboratory of Systems Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, PR China. yxli@sibs.ac.cn.
authors.forename: Tao
authors.initials: T
authors.lastname: Huang
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.forename: Ziliang
authors.initials: Z
authors.lastname: Qian
authors.forename: Kang
authors.initials: K
authors.lastname: Tu
authors.forename: Yixue
authors.initials: Y
authors.lastname: Li
authors.forename: Lu
authors.initials: L
authors.lastname: Xie