title: Inferring gene expression dynamics via functional regression analysis.
abstract: BACKGROUND
  Temporal gene expression profiles characterize the time-dynamics of expression of specific genes and are increasingly collected in current gene expression experiments. In the analysis of experiments where gene expression is obtained over the life cycle, it is of interest to relate temporal patterns of gene expression associated with different developmental stages to each other to study patterns of long-term developmental gene regulation. We use tools from functional data analysis to study dynamic changes by relating temporal gene expression profiles of different developmental stages to each other.
  
  
  RESULTS
  We demonstrate that functional regression methodology can pinpoint relationships that exist between temporary gene expression profiles for different life cycle phases and incorporates dimension reduction as needed for these high-dimensional data. By applying these tools, gene expression profiles for pupa and adult phases are found to be strongly related to the profiles of the same genes obtained during the embryo phase. Moreover, one can distinguish between gene groups that exhibit relationships with positive and others with negative associations between later life and embryonal expression profiles. Specifically, we find a positive relationship in expression for muscle development related genes, and a negative relationship for strictly maternal genes for Drosophila, using temporal gene expression profiles.
  
  
  CONCLUSIONS
  Our findings point to specific reactivation patterns of gene expression during the Drosophila life cycle which differ in characteristic ways between various gene groups. Functional regression emerges as a useful tool for relating gene expression patterns from different developmental stages, and avoids the problems with large numbers of parameters and multiple testing that affect alternative approaches.
authors.affiliation: Department of Statistics, University of California, One Shields Avenue, Davis, CA 95616, USA. mueller@wald.ucdavis.edu
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Müller
authors.forename: Jeng-Min
authors.initials: JM
authors.lastname: Chiou
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Leng
mesh_terms: D000375:Aging / Q000502:physiology; D000465:Algorithms; D000818:Animals; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology / Q000502:physiology*; D020869:Gene Expression Profiling / Q000379:methods*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D008954:Models, Biological; D009024:Morphogenesis / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D012044:Regression Analysis; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins