A Reaction-Diffusion Network model predicts a dual role of Cactus/IκB to regulate Dorsal/NFκB nuclear translocation in<i>Drosophila</i>

Barros, Claudio D. T.; Cardoso, Maira Arruda; Bisch, Paulo Mascarello; Araujo, Helena; Lopes, Francisco J. P.

doi:10.1101/2020.01.18.909416

Cited by 1 publication

(1 citation statement)

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“…For example, Cact degradation on the ventral side of the embryo creates a driving force for a ventrally-directed net flux of Dl/Cact complex, which has the overall effect of shuttling Dl to the ventral side (Carrell et al, 2017). Furthermore, recent experimental and modeling work has suggested that Cact potentiates nuclear translocation on the ventral side of the embryo (Barros et al, 2021;Cardoso et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

Dorsal/NF-κB exhibits a dorsal-to-ventral mobility gradient in the Drosophila embryo

Asafen

Yousef

2018

Preprint

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Morphogen-mediated patterning is a highly dynamic developmental process. To obtain an accurate understanding of morphogen gradients, biophysical parameters such as protein diffusivities must be quantified in vivo. The dorsal-ventral (DV) patterning of early Drosophila embryos by the NF-κB homolog Dorsal (Dl) is an excellent system for understanding morphogen gradient formation. Dl gradient formation is controlled by the inhibitor Cactus/IκB (Cact), which regulates the nuclear import and diffusion of Dl protein. However, quantitative measurements of spatiotemporal Dl movement are currently lacking. Here, we use scanning fluorescence correlation spectroscopy to quantify the mobility of Dl. We find that the diffusivity of Dl varies along the DV axis, with lowest diffusivities on the ventral side, and the DV asymmetry in diffusivity is exclusive to the nuclei. Moreover, we also observe that nuclear export rates are lower in the ventral and lateral regions of the embryo. Both cross correlation spectroscopy measurements and a computational model of Dl/DNA binding suggest that DNA binding of Dl, which is more prevalent on the ventral side of the embryo, is correlated to a lower diffusivity and nuclear export rate. We propose that the variation in Dl/DNA binding along the DV axis is dependent on Cact binding Dl, which prevents Dl from binding DNA in dorsal and lateral regions of the embryo. Thus, our results highlight the complexity of morphogen gradient dynamics and the need for quantitative measurements of biophysical interactions in such systems. Significance StatementTissues in developing organisms are patterned through signaling mechanisms that utilize morphogen concentration gradients. To better understand how these gradients form and are maintained, biophysical parameters such as protein diffusivities must be quantified in vivo. Here, we use scanning fluorescence correlation spectroscopy to quantify the mobility of the morphogen Dorsal (Dl) in the Drosophila embryo. We find that both the diffusivity and nuclear export rate of Dl varies along the dorsal-to-ventral axis, with the lowest values on the ventral side. Moreover, incorporating these experimentally determined diffusion coefficients into a mathematical model suggests that DNA binding of Dl correlates with lower Dl movement. Thus, our results highlight how quantitative measurements of biophysical parameters can improve our understanding of morphogen gradient dynamics.

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Section: Discussionmentioning

confidence: 99%