title: Probing the limits to positional information.
abstract: The reproducibility and precision of biological patterning is limited by the accuracy with which concentration profiles of morphogen molecules can be established and read out by their targets. We consider four measures of precision for the Bicoid morphogen in the Drosophila embryo: the concentration differences that distinguish neighboring cells, the limits set by the random arrival of Bicoid molecules at their targets (which depends on absolute concentration), the noise in readout of Bicoid by the activation of Hunchback, and the reproducibility of Bicoid concentration at corresponding positions in multiple embryos. We show, through a combination of different experiments, that all of these quantities are approximately 10%. This agreement among different measures of accuracy indicates that the embryo is not faced with noisy input signals and readout mechanisms; rather, the system exerts precise control over absolute concentrations and responds reliably to small concentration differences, approaching the limits set by basic physical principles.
authors.affiliation: Joseph Henry Laboratories of Physics, Princeton University, Princeton, NJ 08544, USA. tg2@princeton.edu
authors.forename: Thomas
authors.initials: T
authors.lastname: Gregor
authors.forename: David W
authors.initials: DW
authors.lastname: Tank
authors.forename: Eric F
authors.initials: EF
authors.lastname: Wieschaus
authors.forename: William
authors.initials: W
authors.lastname: Bialek
mesh_terms: D000818:Animals; D019521:Body Patterning; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000196:embryology* / Q000235:genetics; D006454:Hemoglobins / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008433:Mathematics; D008954:Models, Biological; D009024:Morphogenesis / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D006454:Hemoglobins; D018398:Homeodomain Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C056478:bcd protein, Drosophila; C061245:hb protein, Drosophila