Biology subjects

Sokol, S.

Publications and source records attributed to Sokol, S..

4 recordsLinked to original sources

bioRxiv2021

Frizzled3 inhibits Vangl2-Prickle3 association to establish planar cell polarity in the vertebrate neural plate

The orientation of epithelial cells in the plane of the tissue, known as planar cell polarity (PCP), is regulated by interactions of asymmetrically localized PCP protein complexes. In the Xenopus neural plate, Van Gogh-like2 (Vangl2) and Prickle3 (Pk3) proteins form a complex at the anterior cell boundaries, but how this complex is regulated in vivo remains largely unknown. Here we show that Vangl2-Pk3 association is inhibited by Frizzled3 (Fz3), a core PCP protein that is specifically expressed in the neuroectoderm and is essential for the establishment of PCP in this tissue. Proximity biotinylation and crosslinking studies revealed that the Vangl2-Pk3 interaction is suppressed by overexpressed Fz3, but enhanced in Fz3 morphants. In addition, Fz3 induced Vangl2 phosphorylation on T76 and T78, and this phosphorylation was required for Fz3-mediated inhibition of Vangl2-Pk3 complex formation. Consistent with this observation, the complex of Pk3 with nonphosphorylatable Vangl2 was not polarized in the neural plate. These findings provide evidence for in vivo regulation of the Vangl2-Pk3 complex formation and localization by a Frizzled receptor.

developmental biology↗

bioRxiv2021

The dorsal blastopore lip is a source of signals inducing PCP in the Xenopus neural plate

Coordinated polarization of cells in the tissue plane, known as planar cell polarity (PCP), is associated with a signaling pathway critical for the control of morphogenetic processes. Although the segregation of PCP components to opposite cell borders is believed to play a critical role in this pathway, whether PCP derives from egg polarity or preexistent long-range gradient, or forms in response to a localized cue remains a challenging question. Here we investigate the Xenopus neural plate, a tissue that has been previously shown to exhibit PCP. By imaging Vangl2 and Prickle3, we show that PCP is progressively acquired in the neural plate and requires a signal from the posterior region of the embryo. Tissue transplantations indicated that PCP is triggered in the neural plate by a planar cue from the dorsal blastopore lip. The PCP cue did not depend on the orientation of the graft and was distinct from neural inducers. These observations suggest that neuroectodermal PCP is not instructed by a preexisting molecular gradient, but induced by a signal from the dorsal blastopore lip. HighlightsO_LIThe Xenopus neural plate progressively acquires PCP in a posterior-to-anterior direction. C_LIO_LIThe dorsal blastopore lip is likely the source of the PCP-instructing signal for the Xenopus neural plate. C_LIO_LIThe PCP cue is distinct from neural inducers and has a planar mode of transmission. C_LI

developmental biology↗

bioRxiv2021

Pinhead antagonizes Admp to promote notochord formation

Dorsoventral patterning of a vertebrate embryo critically depends on the activity of Smad1 that mediates signaling by several BMP proteins, anti-dorsalizing morphogenetic protein (Admp), and their antagonists. Pinhead (Pnhd), a cystine-knot-containing secreted protein, is expressed in the ventrolateral marginal zone during Xenopus gastrulation, however, its molecular targets and signaling mechanisms have not been fully elucidated. An unbiased mass spectrometry-based screen of the gastrula secretome identified Admp as a primary Pnhd-associated protein. We show that Pnhd binds Admp and inhibits its ventralizing activity by reducing Smad1 phosphorylation and suppressing its transcriptional targets. By contrast, Pnhd did not affect the signaling activity of BMP4. Importantly, the Admp gain-of-function phenotype and phospho-Smad1 levels have been enhanced after Pnhd depletion. Furthermore, Pnhd strongly synergized with Chordin and a truncated BMP4 receptor in the induction of notochord markers in ectoderm cells, and Pnhd-depleted embryos displayed notochord defects. Our findings suggest that Pnhd binds and inactivates Admp to promote notochord development. We propose that the interaction between Admp and Pnhd refines Smad1 activity gradients during vertebrate gastrulation.

developmental biology↗

bioRxiv2021

IsoSolve: an integrative framework to improve isotopic coverage and consolidate isotopic measurements by MS and/or NMR

Stable-isotope labeling experiments are widely used to investigate the topology and functioning of metabolic networks. Label incorporation into metabolites can be quantified using a broad range of mass spectrometry (MS)and nuclear magnetic resonance (NMR)spectroscopy methods, but in general, no single approach can completely cover isotopic space, even for small metabolites. The number of quantifiable isotopic species could be increased, and the coverage of isotopic space improved, by integrating measurements obtained by different methods; however, this approach has remained largely unexplored because no framework able to deal with partial, heterogeneous isotopic measurements has yet been developed. Here, we present a generic computational framework based on symbolic calculus that can integrate any isotopic dataset by connecting measurements to the chemical structure of the molecules. As a test case, we apply this framework to isotopic analyses of amino acids, which are ubiquitous to life, central to many biological questions, and can be analyzed by a broad range of MS and NMR methods. We demonstrate how this integrative framework helps to i) clarify and improve the coverage of isotopic space, ii) evaluate the complementarity and redundancy of different techniques, iii) consolidate isotopic datasets, iv) design experiments, and v) guide future analytical developments. This framework, which can be applied to any labeled element, isotopic tracer, metabolite, and analytical platform, has been implemented in IsoSolve (available at https://github.com/MetaSysLISBP/IsoSolve and https://pypi.org/project/IsoSolve), an open source software that can be readily integrated into data analysis pipelines.

systems biology↗