Gene regulatory networks, axis specification and morphogenesis of the sea urchin embryo
- Understanding how morphogenesis of the embryo is encoded in the sequence of DNA.
- Understanding how morphogens of the TGF beta family work to pattern the embryo.
- Dissecting out the role of maternal determinants and zygotic genes in axis formation.
- Understanding the logic and the evolution of complex gene regulatory networks driving early development
Our goal is to answer fundamental questions such as how an embryo with multiple differentiated cell types can develop from the egg and how is the linear information encoded in the DNA used to shape the embryo during gastrulation and morphogenesis. We try to understand how the main axes of polarity (dorsal-ventral and left-right) are specified and what are the respective roles of the maternal information stored in the egg and of intercellular communication in these processes.
We are also interested in the mechanisms regulating morphogenesis of the larval skeleton, a process that requires epithelial-mesenchymal transition (EMT) and oriented migration of skeletogenic precursors cells located at the vegetal pole of the embryo. We try to understand how beta catenin and MAPK signaling act together with transcription factors to control delamination of these cells and how signals emitted by the ectoderm regulate migration of these mesenchymal cells and control patterning of the skeleton.
We exploit the power of functional analysis and molecular genetics in the developing sea urchin embryo to dissect the processes of axis formation and morphogenesis. Echinoderms are phylogenetically close to vertebrates and their embryos offer many advantages for the functional analysis of developmental genes. In particular, sea urchin embryos are abundant, fully transparent, develop rapidly and synchronously and are amenable to various experimental perturbations such as mRNA overexpression, microinjection of antisense morpholino oligonucleotides or of CRISPER-Cas9 RNAs, or cell transplantation.
Our strategy is based on the analysis of key signaling molecules and transcription factors. In particular, we analyze the roles of morphogens such as Nodal, BMPs and FGFs that play crucial roles in formation of the dorsal-ventral and left-right axes and of kinases and transcription factors of the homeobox and ETS families that are critical regulators of EMT and morphogenesis of skeleton. We use a combination of biochemistry, molecular genetics and imaging to dissect the function of individual genes in these process as well as large scale approaches and genome wide screens such as RNA-seq to reconstruct the Gene Regulatory Networks that orchestrate these processes.
As a broad approach to sea urchin development, we are also doing a large-scale in situ screen which has already generated a number of useful markers for studying specification of cell fates and patterning of the embryo.
Dissect and model the D/V gene regulatory network activated by Nodal and BMP2/4
One objective is to characterize the maternal factors that shape the Nodal and BMP gradients.To reach this goal, we analyze the function of several maternal factors that we recently identified and that appear to be critical regulators of nodal expression. A second objective is to use RNA-seq screens to extend the gene regulatory network activated by Nodal and BMP2/4 and to construct a logical model of this GRN.
Identify the signals that activate MAP kinase signaling and that regulate EMT and morphogenesis of the skeleton.
One objective is to identify the signals activated by beta catenin signaling that trigger MAPK signaling in the skeletogenic mesoderm. Another objective is to identify the key targets phosphorylated by ERK and the transcription factors that orchestrate the EMT genetic program and morphogenesis of the skeleton.
Dissect the early steps leading to establishment of left right asymmetry.
The main objective is to identify the signals that control establishment of the left-right mesendodermal organizer and to understand how the activity of the H+/K+ proton pump, of the Notch/Delta, BMP and FGF signaling pathways act in concert to establish the asymmetrical expression of nodal.
- Molina, MD, Quirin, M, Haillot, E, De Crozé, N, Range, R, Rouel, M et al.. MAPK and GSK3/ß-TRCP-mediated degradation of the maternal Ets domain transcriptional repressor Yan/Tel controls the spatial expression of nodal in the sea urchin embryo. PLoS Genet. 2018;14 (9):e1007621. doi: 10.1371/journal.pgen.1007621. PubMed PMID:30222786 .
- Molina, MD, Quirin, M, Haillot, E, Jimenez, F, Chessel, A, Lepage, T et al.. p38 MAPK as an essential regulator of dorsal-ventral axis specification and skeletogenesis during sea urchin development: a re-evaluation. Development. 2017;144 (12):2270-2281. doi: 10.1242/dev.152330. PubMed PMID:28507001 .
- Karakostis, K, Zanella-Cléon, I, Immel, F, Guichard, N, Dru, P, Lepage, T et al.. A minimal molecular toolkit for mineral deposition? Biochemistry and proteomics of the test matrix of adult specimens of the sea urchin Paracentrotus lividus. J Proteomics. 2016;136 :133-44. doi: 10.1016/j.jprot.2016.01.001. PubMed PMID:26778142 .
- Lapraz, F, Haillot, E, Lepage, T. A deuterostome origin of the Spemann organiser suggested by Nodal and ADMPs functions in Echinoderms. Nat Commun. 2015;6 :8927. doi: 10.1038/ncomms9927. PubMed PMID:26582589 .
- Lapraz, F, Haillot, E, Lepage, T. A deuterostome origin of the Spemann organiser suggested by Nodal and ADMPs functions in Echinoderms. Nat Commun. 2015;6 :8434. doi: 10.1038/ncomms9434. PubMed PMID:26423516 PubMed Central PMC4600745.
- Haillot, E, Molina, MD, Lapraz, F, Lepage, T. The Maternal Maverick/GDF15-like TGF-β Ligand Panda Directs Dorsal-Ventral Axis Formation by Restricting Nodal Expression in the Sea Urchin Embryo. PLoS Biol. 2015;13 (9):e1002247. doi: 10.1371/journal.pbio.1002247. PubMed PMID:26352141 PubMed Central PMC4564238.
- Molina, MD, de Crozé, N, Haillot, E, Lepage, T. Nodal: master and commander of the dorsal-ventral and left-right axes in the sea urchin embryo. Curr. Opin. Genet. Dev. 2013;23 (4):445-53. doi: 10.1016/j.gde.2013.04.010. PubMed PMID:23769944 .
- Bessodes, N, Haillot, E, Duboc, V, Röttinger, E, Lahaye, F, Lepage, T et al.. Reciprocal signaling between the ectoderm and a mesendodermal left-right organizer directs left-right determination in the sea urchin embryo. PLoS Genet. 2012;8 (12):e1003121. doi: 10.1371/journal.pgen.1003121. PubMed PMID:23271979 PubMed Central PMC3521660.
- Range, R, Lepage, T. Maternal Oct1/2 is required for Nodal and Vg1/Univin expression during dorsal-ventral axis specification in the sea urchin embryo. Dev. Biol. 2011;357 (2):440-9. doi: 10.1016/j.ydbio.2011.07.005. PubMed PMID:21782809 .
- Croce, J, Range, R, Wu, SY, Miranda, E, Lhomond, G, Peng, JC et al.. Wnt6 activates endoderm in the sea urchin gene regulatory network. Development. 2011;138 (15):3297-306. doi: 10.1242/dev.058792. PubMed PMID:21750039 PubMed Central PMC3133919.
- Saudemont, A, Haillot, E, Mekpoh, F, Bessodes, N, Quirin, M, Lapraz, F et al.. Ancestral regulatory circuits governing ectoderm patterning downstream of Nodal and BMP2/4 revealed by gene regulatory network analysis in an echinoderm. PLoS Genet. 2010;6 (12):e1001259. doi: 10.1371/journal.pgen.1001259. PubMed PMID:21203442 PubMed Central PMC3009687.
- Duboc, V, Lapraz, F, Saudemont, A, Bessodes, N, Mekpoh, F, Haillot, E et al.. Nodal and BMP2/4 pattern the mesoderm and endoderm during development of the sea urchin embryo. Development. 2010;137 (2):223-35. doi: 10.1242/dev.042531. PubMed PMID:20040489 .
- Lapraz, F, Besnardeau, L, Lepage, T. Patterning of the dorsal-ventral axis in echinoderms: insights into the evolution of the BMP-chordin signaling network. PLoS Biol. 2009;7 (11):e1000248. doi: 10.1371/journal.pbio.1000248. PubMed PMID:19956794 PubMed Central PMC2772021.
- Duboc, V, Lapraz, F, Besnardeau, L, Lepage, T. Lefty acts as an essential modulator of Nodal activity during sea urchin oral-aboral axis formation. Dev. Biol. 2008;320 (1):49-59. doi: 10.1016/j.ydbio.2008.04.012. PubMed PMID:18582858 .
- Röttinger, E, Saudemont, A, Duboc, V, Besnardeau, L, McClay, D, Lepage, T et al.. FGF signals guide migration of mesenchymal cells, control skeletal morphogenesis [corrected] and regulate gastrulation during sea urchin development. Development. 2008;135 (2):353-65. doi: 10.1242/dev.014282. PubMed PMID:18077587 .
- Range, R, Lapraz, F, Quirin, M, Marro, S, Besnardeau, L, Lepage, T et al.. Cis-regulatory analysis of nodal and maternal control of dorsal-ventral axis formation by Univin, a TGF-beta related to Vg1. Development. 2007;134 (20):3649-64. doi: 10.1242/dev.007799. PubMed PMID:17855430 .
- Sea Urchin Genome Sequencing Consortium, Sodergren, E, Weinstock, GM, Davidson, EH, Cameron, RA, Gibbs, RA et al.. The genome of the sea urchin Strongylocentrotus purpuratus. Science. 2006;314 (5801):941-52. doi: 10.1126/science.1133609. PubMed PMID:17095691 PubMed Central PMC3159423.
- Lapraz, F, Röttinger, E, Duboc, V, Range, R, Duloquin, L, Walton, K et al.. RTK and TGF-beta signaling pathways genes in the sea urchin genome. Dev. Biol. 2006;300 (1):132-52. doi: 10.1016/j.ydbio.2006.08.048. PubMed PMID:17084834 .
- Röttinger, E, Besnardeau, L, Lepage, T. Expression pattern of three putative RNA-binding proteins during early development of the sea urchin Paracentrotus lividus. Gene Expr. Patterns. 2006;6 (8):864-72. . PubMed PMID:17061352 .
- Röttinger, E, Croce, J, Lhomond, G, Besnardeau, L, Gache, C, Lepage, T et al.. Nemo-like kinase (NLK) acts downstream of Notch/Delta signalling to downregulate TCF during mesoderm induction in the sea urchin embryo. Development. 2006;133 (21):4341-53. doi: 10.1242/dev.02603. PubMed PMID:17038519 .
2009 - Prix Tregouboff in Marine Biology, French Academy of Sciences
2007 - Prize "Coup d'élan pour la recherche", Bettencourt-Schueller Foundation
1995 - Fellowship Human Frontiers, HFSP
Postdoctoral Fellowship in Developmental Biology
Analysis of the regulatory landscapes associated with Nodal and BMP2/4 signalling by Assays for Tansposase Accessible Chromatin using sequencing (ATAC-Seq)
A two-year postdoctoral position supported by the French Foundation for Medical Research (FRM) is available starting September 1st 2018 to work in the group Gene regulatory networks, axis specification and morphogenesis of the sea urchin embryo at the Institute of Biology Valrose.
The area of research will concern the analysis of transcriptional regulation downstream of Nodal and BMP2/4 signalling in the sea urchin embryo (see Lapraz F, Haillot E, and Lepage,T – 2015 – A deuterostome origin of the Spemann organiser suggested by Nodal and ADMPs functions in Echinoderms; Nature communications and Haillot E, Molina MD, Lapraz F, and Lepage,T (2015) The Maternal Maverick/GDF15-like TGF-β Ligand Panda Directs Dorsal-Ventral Axis Formation by Restricting Nodal Expression in the Sea Urchin Embryo. – 2015 – PLoS Biology.
Our laboratory has recently performed large-scale analyses of chromatin accessibility in wild type embryos and following over-activation of the Nodal and BMP2/4 pathways by ATAC-seq. In addition, we have recently obtained high-quality developmental transcriptomes and a high-quality genome assembly
for the Mediterranean sea urchin Paracentrotus lividus.
The postdoctoral project will aim at integrating the results of these “omics” screens in the analysis of the dorsal ventral gene regulatory network. In particular, the project will focus on the identification of the transcription factors regulating nodal expression identified by ATAC-seq. It will also aim at identifying the cis-regulatory regions of the Nodal and BMP2/4 target genes and explore the regulatory landscapes associated with Nodal and BMP signaling.
Candidates should have obtained recently a PhD degree. Both national and international candidates are encouraged to apply. Interested candidates should send a Curriculum Vitae, a summary of research interests and goals and contact information for two or three referees to:
Institut de Biologie Valrose
CNRS UMR7277 – Inserm U1091
Université Nice Sophia Antipolis 06108 Cedex 2 France
iBV - Institut de Biologie Valrose
Université Nice Sophia Antipolis
Faculté des Sciences
06108 Nice cedex 2