title: The role of cell location and spatial gradients in the evolutionary dynamics of colon and intestinal crypts.
abstract: Colon and intestinal crypts serve as an important model system for adult stem cell proliferation and differentiation. We develop a spatial stochastic model to study the rate of somatic evolution in a normal crypt, focusing on the production of two-hit mutants that inactivate a tumor suppressor gene. We investigate the effect of cell division pattern along the crypt on mutant production, assuming that the division rate of each cell depends on its location.
  
  
  
  We find that higher probability of division at the bottom of the crypt, where the stem cells are located, leads to a higher rate of double-hit mutant production. The optimal case for delaying mutations occurs when most of the cell divisions happen at the top of the crypt. We further consider an optimization problem where the "evolutionary" penalty for double-hit mutant generation is complemented with a "functional" penalty that assures that fully differentiated cells at the top of the crypt cannot divide.
  
  
  
  The trade-off between the two types of objectives leads to the selection of an intermediate division pattern, where the cells in the middle of the crypt divide with the highest rate. This matches the pattern of cell divisions obtained experimentally in murine crypts.
  
  
  
  This article was reviewed by David Axelrod (nominated by an Editorial Board member, Marek Kimmel), Yang Kuang and Anna Marciniak-Czochra. For the full reviews, please go to the Reviewers' comments section.
authors.affiliation: Mathematical Biosciences Institute, The Ohio State University, 1735 Neil Ave, Columbus, 43210, USA.
authors.forename: Leili
authors.initials: L
authors.lastname: Shahriyari
authors.affiliation: Department of Mathematics, University of California Irvine, 340 Rowland Hall, Irvine, 92697, USA. komarova@uci.edu.
authors.forename: Natalia L
authors.initials: NL
authors.lastname: Komarova
authors.affiliation: Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, 153 Hurley Hall, Notre Dame, 46556, USA. ajilkine@nd.edu.
authors.forename: Alexandra
authors.identifier: 0000-0001-5896-5962
authors.initials: A
authors.lastname: Jilkine
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002454:Cell Differentiation; D049109:Cell Proliferation; D003106:Colon / Q000166:cytology / Q000254:growth & development*; D007422:Intestines / Q000166:cytology / Q000254:growth & development*; D051379:Mice; D008957:Models, Genetic; D009154:Mutation; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D013269:Stochastic Processes
keywords: BrdU labeling; Carcinogenesis; Intestinal crypt; Mutation accumulation; Optimization; Stochastic model; Symmetric division; Two hit mutant