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Activation of pmar1 controls specification of micromeres in the sea urchin embryo

Oliveri, Paola and Davidson, Eric H. and McClay, David R. (2003) Activation of pmar1 controls specification of micromeres in the sea urchin embryo. Developmental Biology, 258 (1). pp. 32-43. ISSN 0012-1606. doi:10.1016/S0012-1606(03)00108-8.

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pmar1 is a transcription factor in the paired class homeodomain family that was identified and found to be transcribed in micromeres beginning at the fourth cleavage of sea urchin development [Dev. Biol. 246 (2002), 209]. Based on in situ data, molecular perturbation studies, and QPCR data, the recently published gene regulatory network (GRN) model for endomesoderm specification [Science 295 (2002) 1669; Dev. Biol. 246 (2002), 162] places pmar1 early in the micromere specification pathway, and upstream of two important micromere induction signals. The goal of this study was to test these three predictions of the network model. A series of embryo chimeras were produced in which pmar1 activity was perturbed in one cell that was transplanted to control hosts. At the fourth cleavage, micromeres bearing altered pmar1 activity were combined with a normal micromereless host embryo. If β-catenin signaling is blocked, the micromeres remain unspecified and are unable to signal to the host cells. When such β-catenin-blocked micromeres also express Pmar1, all observed micromere functions are rescued. The rescue includes expression of the primary mesenchyme cell (PMC) differentiation program, expression and execution of the Delta signal to induce secondary mesoderm cell (SMC) specification in macromere progeny, and expression of the early endomesoderm induction signal necessary for full specification of the endoderm. Additionally, Pmar1 expressed mosaically from inserted DNA constructs causes induction of ectopic Endo 16 in adjacent cells, demonstrating further that Pmar1 controls expression of the early endomesoderm induction signal. Based on these experiments, Pmar1 is an important transcription factor necessary for initiating the micromere specification program and for the expression of two inductive signals produced by micromeres. Each of the tests we describe supports the placement and function of Pmar1 in the endomesoderm GRN model.

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Additional Information:© 2003 Elsevier Science. Received for publication 25 October 2002, revised 5 February 2003, accepted 6 February 2003. Available online 18 April 2003. We thank A. Ransick, C. Bradham, and J. Gross for critical comments on this manuscript, and we thank Lynne Angerer for the SoxB1 antibody. Support for this paper is provided by NIH HD-37105 (to E.H.D.) and GM 61464 (to D.R.M.).
Funding AgencyGrant Number
NIHGM 61464
Subject Keywords:Gene regulatory network; Sox; Delta; β-Catenin; Paired homeodomain
Issue or Number:1
Record Number:CaltechAUTHORS:20160121-075840091
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Official Citation:Paola Oliveri, Eric H Davidson, David R McClay, Activation of pmar1 controls specification of micromeres in the sea urchin embryo, Developmental Biology, Volume 258, Issue 1, 1 June 2003, Pages 32-43, ISSN 0012-1606, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63825
Deposited By: Ruth Sustaita
Deposited On:21 Jan 2016 18:57
Last Modified:10 Nov 2021 23:21

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