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Noise modulation in retinoic acid signaling sharpens segmental boundaries of gene expression in the embryonic zebrafish hindbrain.

Sosnik J, Zheng L, Rackauckas CV, Digman M, Gratton E, Nie Q, Schilling TF - Elife (2016)

Bottom Line: We demonstrate that RA forms a noisy gradient during critical stages of hindbrain patterning and that cells use distinct intracellular binding proteins to attenuate noise in RA levels.Increasing noise disrupts sharpening of rhombomere boundaries and proper patterning of the hindbrain.These findings reveal novel cellular mechanisms of noise regulation, which are likely to play important roles in other aspects of physiology and disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental and Cell Biology, University of California, Irvine, Irvine, United States.

ABSTRACT
Morphogen gradients induce sharply defined domains of gene expression in a concentration-dependent manner, yet how cells interpret these signals in the face of spatial and temporal noise remains unclear. Using fluorescence lifetime imaging microscopy (FLIM) and phasor analysis to measure endogenous retinoic acid (RA) directly in vivo, we have investigated the amplitude of noise in RA signaling, and how modulation of this noise affects patterning of hindbrain segments (rhombomeres) in the zebrafish embryo. We demonstrate that RA forms a noisy gradient during critical stages of hindbrain patterning and that cells use distinct intracellular binding proteins to attenuate noise in RA levels. Increasing noise disrupts sharpening of rhombomere boundaries and proper patterning of the hindbrain. These findings reveal novel cellular mechanisms of noise regulation, which are likely to play important roles in other aspects of physiology and disease.

No MeSH data available.


Related in: MedlinePlus

Crabp2a actively modulates RA signal noise.Results of three realizations of our stochastic mathematical model analyzing the temporal distribution of RA’s relative abundance in wildtype (WT), Crabp2a morpholino (MO)-injected, Crabp2a mRNA (gain-of-function - GOF) injected, Cyp26a1 MO-injected and Cyp26a1 mRNA-injected zebrafish embryos. Each column shows the signal obtained for a single realization for a single cell. Each point corresponds to a single time point. Lines represent the mean and standard deviation. Embryos with altered Crabp2a expression show changes in the variability in free intracellular RA, while embryos with altered Cyp26a1 expression show changes in the mean levels of RA as in the experimental case shown in Figure 3.DOI:http://dx.doi.org/10.7554/eLife.14034.009
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fig3s1: Crabp2a actively modulates RA signal noise.Results of three realizations of our stochastic mathematical model analyzing the temporal distribution of RA’s relative abundance in wildtype (WT), Crabp2a morpholino (MO)-injected, Crabp2a mRNA (gain-of-function - GOF) injected, Cyp26a1 MO-injected and Cyp26a1 mRNA-injected zebrafish embryos. Each column shows the signal obtained for a single realization for a single cell. Each point corresponds to a single time point. Lines represent the mean and standard deviation. Embryos with altered Crabp2a expression show changes in the variability in free intracellular RA, while embryos with altered Cyp26a1 expression show changes in the mean levels of RA as in the experimental case shown in Figure 3.DOI:http://dx.doi.org/10.7554/eLife.14034.009

Mentions: If cells actively control noise in RA signaling, they likely do it through intracellular RA-binding proteins, Crabps, or RA-degrading enzymes, Cyp26s, that can rapidly alter freely available RA (Kleywegt et al., 1994) and both of which have been shown to play critical roles in RA signaling (Sirbu et al., 2005; Hernandez et al., 2007; White et al., 2007; Cai et al., 2012). To test these candidates we reduced the amount (microinjected MOs) or overexpressed (microinjected mRNA) Crabp2a and Cyp26a1 in zebrafish embryos and measured noise in RA at mid-gastrula stages. Strikingly, MO depletion of Crabp2a increased temporal noise in RA without altering the mean RA level at a given A-P position, while overexpression of Crabp2a decreased variability in RA, again without altering the mean levels of RA (Figure 3). In contrast depletion or overexpression of Cyp26a1 increased or decreased mean RA levels, respectively, without altering noise. These results agree with simulations using our stochastic mathematical model in which we altered the levels of Crabp2a or Cyp26a1 (Figure 3—figure supplement 1). These results reveal a novel, active role for Crabps in modulating noise in RA.10.7554/eLife.14034.008Figure 3.Crabp2a but not Cyp26a1 attenuates level of noise in RA.


Noise modulation in retinoic acid signaling sharpens segmental boundaries of gene expression in the embryonic zebrafish hindbrain.

Sosnik J, Zheng L, Rackauckas CV, Digman M, Gratton E, Nie Q, Schilling TF - Elife (2016)

Crabp2a actively modulates RA signal noise.Results of three realizations of our stochastic mathematical model analyzing the temporal distribution of RA’s relative abundance in wildtype (WT), Crabp2a morpholino (MO)-injected, Crabp2a mRNA (gain-of-function - GOF) injected, Cyp26a1 MO-injected and Cyp26a1 mRNA-injected zebrafish embryos. Each column shows the signal obtained for a single realization for a single cell. Each point corresponds to a single time point. Lines represent the mean and standard deviation. Embryos with altered Crabp2a expression show changes in the variability in free intracellular RA, while embryos with altered Cyp26a1 expression show changes in the mean levels of RA as in the experimental case shown in Figure 3.DOI:http://dx.doi.org/10.7554/eLife.14034.009
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4829421&req=5

fig3s1: Crabp2a actively modulates RA signal noise.Results of three realizations of our stochastic mathematical model analyzing the temporal distribution of RA’s relative abundance in wildtype (WT), Crabp2a morpholino (MO)-injected, Crabp2a mRNA (gain-of-function - GOF) injected, Cyp26a1 MO-injected and Cyp26a1 mRNA-injected zebrafish embryos. Each column shows the signal obtained for a single realization for a single cell. Each point corresponds to a single time point. Lines represent the mean and standard deviation. Embryos with altered Crabp2a expression show changes in the variability in free intracellular RA, while embryos with altered Cyp26a1 expression show changes in the mean levels of RA as in the experimental case shown in Figure 3.DOI:http://dx.doi.org/10.7554/eLife.14034.009
Mentions: If cells actively control noise in RA signaling, they likely do it through intracellular RA-binding proteins, Crabps, or RA-degrading enzymes, Cyp26s, that can rapidly alter freely available RA (Kleywegt et al., 1994) and both of which have been shown to play critical roles in RA signaling (Sirbu et al., 2005; Hernandez et al., 2007; White et al., 2007; Cai et al., 2012). To test these candidates we reduced the amount (microinjected MOs) or overexpressed (microinjected mRNA) Crabp2a and Cyp26a1 in zebrafish embryos and measured noise in RA at mid-gastrula stages. Strikingly, MO depletion of Crabp2a increased temporal noise in RA without altering the mean RA level at a given A-P position, while overexpression of Crabp2a decreased variability in RA, again without altering the mean levels of RA (Figure 3). In contrast depletion or overexpression of Cyp26a1 increased or decreased mean RA levels, respectively, without altering noise. These results agree with simulations using our stochastic mathematical model in which we altered the levels of Crabp2a or Cyp26a1 (Figure 3—figure supplement 1). These results reveal a novel, active role for Crabps in modulating noise in RA.10.7554/eLife.14034.008Figure 3.Crabp2a but not Cyp26a1 attenuates level of noise in RA.

Bottom Line: We demonstrate that RA forms a noisy gradient during critical stages of hindbrain patterning and that cells use distinct intracellular binding proteins to attenuate noise in RA levels.Increasing noise disrupts sharpening of rhombomere boundaries and proper patterning of the hindbrain.These findings reveal novel cellular mechanisms of noise regulation, which are likely to play important roles in other aspects of physiology and disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental and Cell Biology, University of California, Irvine, Irvine, United States.

ABSTRACT
Morphogen gradients induce sharply defined domains of gene expression in a concentration-dependent manner, yet how cells interpret these signals in the face of spatial and temporal noise remains unclear. Using fluorescence lifetime imaging microscopy (FLIM) and phasor analysis to measure endogenous retinoic acid (RA) directly in vivo, we have investigated the amplitude of noise in RA signaling, and how modulation of this noise affects patterning of hindbrain segments (rhombomeres) in the zebrafish embryo. We demonstrate that RA forms a noisy gradient during critical stages of hindbrain patterning and that cells use distinct intracellular binding proteins to attenuate noise in RA levels. Increasing noise disrupts sharpening of rhombomere boundaries and proper patterning of the hindbrain. These findings reveal novel cellular mechanisms of noise regulation, which are likely to play important roles in other aspects of physiology and disease.

No MeSH data available.


Related in: MedlinePlus