title: Robust patterns in the stochastic organization of filopodia.
abstract: BACKGROUND
  Filopodia are actin-based cellular projections that have a critical role in initiating and sustaining directional migration in vertebrate cells. Filopodia are highly dynamic structures that show a rich diversity in appearance and behavior. While there are several mathematical models of filopodia initiation and growth, testing the capacity of these theoretical models in predicting empirical behavior has been hampered by a surprising shortage of quantitative data related to filopodia. Neither is it clear how quantitatively robust the cellular filopodial network is and how perturbations alter it.
  
  
  RESULTS
  We have measured the length and interfilopodial separation distances of several thousand filopodia in the rodent cell line Rat2 and measured these parameters in response to genetic, chemical and physical perturbation. Our work shows that length and separation distance have a lognormal pattern distribution over their entire detection range (0.4 μm to 50 μm).
  
  
  CONCLUSIONS
  We find that the lognormal distribution of length and separation is robust and highly resistant to perturbation. We also find that length and separation are independent variables. Most importantly, our empirical data is not entirely in agreement with predictions made based on existing theoretical models and that filopodial size and separation are an order of magnitude larger than what existing models suggest.
authors.affiliation: Department of Biochemistry, Microbiology & Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Asma N
authors.initials: AN
authors.lastname: Husainy
authors.forename: Anne A
authors.initials: AA
authors.lastname: Morrow
authors.forename: Theodore J
authors.initials: TJ
authors.lastname: Perkins
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Lee
mesh_terms: D008841:Actin Cytoskeleton / Q000648:ultrastructure; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002460:Cell Line; D015778:Minor Histocompatibility Antigens; D008954:Models, Biological; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011107:Polylysine / Q000494:pharmacology; D011554:Pseudopodia / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats
chemical_list: D015778:Minor Histocompatibility Antigens; D011107:Polylysine; D017853:Phosphotransferases (Alcohol Group Acceptor); C402182:phosphatidylinositol phosphate 4-kinase; D001920:Bradykinin