A gradient of Bicoid protein in

Max-Planck-Institut für Entwicklungsbiologie, Abteilung III Genetik, Tübingen, Federal Republic of Germany.
Cell (Impact Factor: 32.24). 08/1988; 54(1):83-93. DOI: 10.1016/0092-8674(88)90182-1
Source: PubMed

ABSTRACT The maternal gene bicoid (bcd) organizes anterior development in Drosophila. Its mRNA is localized at the anterior tip of the oocyte and early embryo. Antibodies raised against bcd fusion proteins recognize a 55-57 kd doublet band in Western blots of extracts of 0-4 hr old embryos. This protein is absent or reduced in embryonic extracts of nine of the 11 bcd alleles. The protein is concentrated in the nuclei of cleavage stage embryos. It cannot be detected in oocytes, indicating temporal control of bcd mRNA translation. The bcd protein is distributed in an exponential concentration gradient with a maximum at the anterior tip, reaching background levels in the posterior third of the embryo. The gradient is probably generated by diffusion from the local mRNA source and dispersed degradation.

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    • "Similar patterns of broad subdivision followed by shortrange refinement are found during the specification of the vertebrate neural crest by reiterated rounds of extracellular signaling [22]; in the formation of segmented muscle precursors (somites) by FGF and Notch followed by short range Ephrin activity [23] [24]; the dorsal-ventral patterning of the Drosophila body axis, first by a gradient of NFκB activity (also called Dorsal) and then by members of the BMP family of secreted signaling molecules [25] [26]; and also in the fruit fly, the patterning of the anteriorposterior (AP) axis by gradients of diffusible transcription factors within the shared cytoplasm of the nuclear syncytium [15] [27] [28]. These examples and others illustrate a common theme where long range signaling gradients subdivide a large field into smaller domains, within which the patterned expression of secondary factors establishes elaborated patterns (Fig. 1B). "
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    ABSTRACT: In pattern-forming developmental systems, cells commonly interpret graded input signals, known as morphogens. Morphogens often pattern tissues through cascades of sequential gene expression steps. Such a multi-tiered structure appears to constitute suboptimal use of the positional information provided by the input morphogen because noise is added at each tier. However, the conventional theory neglects the role of the format in which information is encoded. We argue that the relevant performance measure is not solely the amount of information carried by the morphogen, but the amount of information that can be accessed by the downstream network. We demonstrate that quantifying the information that is accessible to the system naturally explains the prevalence of multi-tiered network architectures as a consequence of the noise inherent to the control of gene expression. We support our argument with empirical observations from patterning along the major body axis of the fruit fly embryo.
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    • "The concentration of Bicoid protein is higher near the anterior pole of the embryo and its local concentration decreases as the distance to the anterior pole increases. This is called the Bicoid protein gradient [2] [4]. Recently, bicoid mRNA gradients along the anteroposterior axis of the embryo of Drosophila have been observed [15], clarifying our current views about Drosophila early development. "
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    ABSTRACT: We show that mRNA diffusion is the main morphogenesis mechanism that consistently explains the establishment of Bicoid protein gradients in the embryo of Drosophila, contradicting the current view of protein diffusion. Moreover, we show that if diffusion for both bicoid mRNA and Bicoid protein were assumed, a steady distribution of Bicoid protein with a constant concentration along the embryo would result, contradicting observations. © 2014 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
    Comptes Rendus Biologies 10/2014; 337(12). DOI:10.1016/j.crvi.2014.09.004 · 0.98 Impact Factor
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    • "tually specify unique fates for each of the ∼ 80 rows of cells along the AP axis [11]. Specifically, one of the first patterns is the Bicoid (Bcd) protein gradient whose diffusiondriven exponentially decaying concentration profile along the AP axis [12] [13] is reproducible to within 10% from embryo to embryo [14] [15]. This reproducibility is sufficient for the Bcd gradient to encode position with 1.6% embryo length (EL) precision. "
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    ABSTRACT: Cell fate decisions during multicellular development are precisely coordinated, leading to highly reproducible macroscopic structural outcomes [1-3]. The origins of this reproducibility are found at the molecular level during the earliest stages of development when patterns of morphogen molecules emerge reproducibly [4, 5]. However, although the initial conditions for these early stages are determined by the female during oogenesis, it is unknown whether reproducibility is perpetuated from oogenesis or reacquired by the zygote. To address this issue in the early Drosophila embryo, we sought to count individual maternally deposited bicoid mRNA molecules and compare variability between embryos with previously observed fluctuations in the Bicoid protein gradient [6, 7]. Here, we develop independent methods to quantify total amounts of mRNA in individual embryos and show that mRNA counts are highly reproducible between embryos to within ∼9%, matching the reproducibility of the protein gradient. Reproducibility emerges from perfectly linear feedforward processes: changing the genetic dosage in the female leads to proportional changes in both mRNA and protein numbers in the embryo. Our results indicate that the reproducibility of the morphological structures of embryos originates during oogenesis, which is when the expression of maternally provided patterning factors is precisely controlled.
    Current biology: CB 05/2014; 24(11):1283-1288. DOI:10.1016/j.cub.2014.04.028 · 9.57 Impact Factor
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