Identification of a Core Set of Signature Cell Cycle Genes Whose Relative Order of Time-to-Peak Expression Is Conserved Across Species

• Activity Number: 320
• Type: Topic Contributed
• Date/Time: Tuesday, July 31, 2012 : 10:30 AM to 12:20 PM
• Sponsor: Biometrics Section
• Author(s): Shyamal Peddada*+ and Miguel Fernandez and Cristina Rueda
• Companies: National Institute of Environmental Health Sciences and University of Valladolid and University of Valladolid
• Keywords: Circular order ; Constrained inference ; Conditional test ; Cell cycle genes ; Phase angles

Abstract

Cell cycle in eukaryotes is a well-coordinated process with cells going through four distinct phases before dividing. Genes with periodic expression are known as cell-cycle genes. To discover evolutionarily conserved cell-cycle genes, biologists are often interested in identifying genes that are periodic in multiple organisms. Since cell cycle is a carefully orchestrated process, one may hypothesize that the relative order of time to peak expression among the core set of cell-cycle genes is conserved evolutionarily. In this talk we introduce a novel statistical methodology by formulating the problem of interest as an order restricted inference problem on a unit circle. Standard order restricted inference methods do not directly apply here due to the geometry of the circle. We introduce a simple conditional test, whose null distribution can be approximated by central chi-square distribution, to test the hypothesis of interest. Using the proposed statistical methodology, we discover seven cell-cycle genes whose relative order is potentially conserved evolutionarily. Methodology described in this talk could help biologists formulate and test other similar hypotheses.