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Ossipova, O.

Publications and source records attributed to Ossipova, O..

2 recordsLinked to original sources
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↗