title: Pre-steady-state decoding of the Bicoid morphogen gradient.
abstract: Morphogen gradients are established by the localized production and subsequent diffusion of signaling molecules. It is generally assumed that cell fates are induced only after morphogen profiles have reached their steady state. Yet, patterning processes during early development occur rapidly, and tissue patterning may precede the convergence of the gradient to its steady state. Here we consider the implications of pre-steady-state decoding of the Bicoid morphogen gradient for patterning of the anterior-posterior axis of the Drosophila embryo. Quantitative analysis of the shift in the expression domains of several Bicoid targets (gap genes) upon alteration of bcd dosage, as well as a temporal analysis of a reporter for Bicoid activity, suggest that a transient decoding mechanism is employed in this setting. We show that decoding the pre-steady-state morphogen profile can reduce patterning errors caused by fluctuations in the rate of morphogen production. This can explain the surprisingly small shifts in gap and pair-rule gene expression domains observed in response to alterations in bcd dosage.
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Sven
authors.initials: S
authors.lastname: Bergmann
authors.forename: Oded
authors.initials: O
authors.lastname: Sandler
authors.forename: Hila
authors.initials: H
authors.lastname: Sberro
authors.forename: Sara
authors.initials: S
authors.lastname: Shnider
authors.forename: Eyal
authors.initials: E
authors.lastname: Schejter
authors.forename: Ben-Zion
authors.initials: BZ
authors.lastname: Shilo
authors.forename: Naama
authors.initials: N
authors.lastname: Barkai
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000502:physiology*; D002454:Cell Differentiation / Q000235:genetics; D004330:Drosophila / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D047108:Embryonic Development; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism* / Q000502:physiology
chemical_list: D029721:Drosophila Proteins; D020690:GTPase-Activating Proteins; D018398:Homeodomain Proteins; D015534:Trans-Activators; C056478:bcd protein, Drosophila