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Published March 1, 2015 | public
Journal Article Open

Geometric control of ciliated band regulatory states in the sea urchin embryo


The trapezoidal ciliated band (CB) of the postgastrular sea urchin embryo surrounds the oral ectoderm, separating it from adjacent embryonic territories. Once differentiated, the CB is composed of densely arranged cells bearing long cilia that endow the larva with locomotion and feeding capability. The spatial pattern from which the CB will arise is first evidenced during pregastrular stages by expression of the pioneer gene onecut. Immediately after gastrulation, the CB consists of four separate regulatory state domains, each of which expresses a unique set of transcription factors: (1) the oral apical CB, located within the apical neurogenic field; (2) the animal lateral CB, which bilaterally separates the oral from aboral ectoderm; (3) the vegetal lateral CB, which bilaterally serves as signaling centers; and (4) the vegetal oral CB, which delineates the boundary with the underlying endoderm. Remarkably, almost all of the regulatory genes specifically expressed within these domains are downregulated by interference with SoxB1 expression, implying their common activation by this factor. Here, we show how the boundaries of the CB subdomains are established, and thus ascertain the design principle by which the geometry of this unique and complex regulatory state pattern is genomically controlled. Each of these boundaries, on either side of the CB, is defined by spatially confined transcriptional repressors, the products of regulatory genes operating across the border of each subdomain. In total this requires deployment of about ten different repressors, which we identify in this work, thus exemplifying the complexity of information required for spatial regulatory organization during embryogenesis.

Additional Information

© 2015 Published by The Company of Biologists Ltd. Received 18 September 2014; Accepted 28 December 2014; Posted online before print February 5, 2015. We thank Eric Erkenbrack for the microphotograph shown in Fig. 1A and Klara Stefflova for assistance throughout figure preparation. Funding: This research was supported by the National Institutes of Health [HD067454 to E.H.D.]. Deposited in PMC for release after 12 months. Author contributions: J.C.B. and E.H.D. designed the research; J.C.B. and E.L. performed the research; J.C.B., E.L. and E.H.D. analyzed the data; and J.C.B. and E.H.D. wrote the paper.

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August 20, 2023
August 20, 2023