Spdeadringer, a sea urchin embryo gene required separately in skeletogenic and oral ectoderm gene regulatory networks.
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Spdri encodes an ARID-class transcription factor and is a key node in two separate GRNs (skeletogenic micromere lineage and oral ectoderm).
"The Spdeadringer (Spdri) gene encodes an ARID-class transcription factor not previously known in sea urchin embryos. We show that Spdri is a key player in two separate developmental gene regulatory networks (GRNs)."
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Expression is biphasic, in the skeletogenic large-micromere descendants from 12 h to ingression and then in the oral ectoderm from about 20 h, and in both territories follows prior specification events.
"Spdri is expressed in a biphasic manner, first, after 12 h and until ingression in the skeletogenic descendants of the large micromeres; second, after about 20 h in the oral ectoderm, where its transcripts remain present at 30-50 mRNA molecules/cell far into development. In both territories, the periods of Spdri expression follow prior territorial specification events."
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In the micromere descendants Dri acts in the pathways leading to expression of the terminal skeletogenic gene batteries; morpholino knockdown causes failure of spiculogenesis and of PMC patterning.
"Spdri is shown to act in the micromere descendants in the pathways that result in the expression of batteries of terminal skeletogenic genes."
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Dri is required cell-autonomously in the micromere lineage for skeletogenic gene expression before ingression (micromere transplant chimeras).
"while Spdri expression is required autonomously for expression of skeletogenic genes prior to ingression, complete skeletogenesis also requires the expression of oral ectoderm patterning information."
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In the oral ectoderm Dri participates in the central GRN controlling oral ectoderm identity; knockdown abolishes oral features and the aboral marker spec1 spreads over the whole ectoderm.
"If its expression is blocked by treatment with alphaSpdri MASO, oral-specific features disappear and expression of the aboral ectoderm marker spec1 encompasses the whole of the ectoderm."
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The gastrulation failure after knockdown is indirect and not due to a defect in endomesoderm specification.
"Failure of gastrulation is not due to indirect interference with endomesodermal specification per se, since all endomesodermal genes tested function normally in alphaSpdri MASO embryos."