Sea Urchin Development

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Sea Urchin- 2 cell stage

The sea urchin embryo initially undergoes ten cycles of cell division forming a single epithelial layer enveloping a blastocoel, followed by gastrulation producing the three germ layers. Historically, one of the earliest systems used in developmental biology (H. Driesch, 1892; J. Loeb, 1893; Lillie, 1912[1] Spermatozoa Chemotaxis; S. Horstadius, 1928), this embryo system has been used recently to study early molecular controls of patterning and axis formation.

Sea urchin left-right asymmetry.jpg

Links: Category:Sea Urchin

Some Recent Findings

  • An optogenetic approach to control protein localization during embryogenesis of the sea urchin[2] "Light inducible protein-protein interactions have been used to manipulate protein localization and function in the cell with utmost spatial and temporal precision. In this technical report, we use a recently developed optogenetic approach to manipulate protein localization in the developing sea urchin embryo. A photosensitive LOV domain from Avena sativa phototropin1 cages a small peptide that binds the engineered PDZ domain (ePDZ) upon blue light irradiation. Using this system, mCherry tagged proteins fused with the LOV domain were recruited to ectopic sub-cellular regions such as the membrane, microtubules, or actin by GFP tagged proteins fused with the ePDZ domain upon blue light irradiation within 1-3 min in the sea urchin embryo....Continuous blue light activation with a regular blue aquarium light over two days of culture successfully induced LOV-ePDZ binding in the developing embryos, resulting in continued ectopic recruitment of Vasa and failure in gastrulation at Day 2. Although some cytotoxicity was observed with prolonged blue light irradiation, this optogenetic system provides a promising approach to test the sub-cellular activities of developmental factors, as well as to alter protein localization and development during embryogenesis."
  • Single nucleotide editing without DNA cleavage using CRISPR/Cas9-deaminase in the sea urchin embryo[3] "In this study, we demonstrate a modified CRISPR/Cas9 system fused to cytosine deaminase (Cas9-DA), which induces a single nucleotide conversion in the genome. Cas9-DA was introduced into sea urchin eggs with sgRNAs targeted for SpAlx1, SpDsh, or SpPks, each of which is critical for skeletogenesis, embryonic axis formation, or pigment formation, respectively. We found that both Cas9 and Cas9-DA edit the genome, and cause predicted phenotypic changes at a similar efficiency. Cas9, however, resulted in significant deletions in the genome centered on the gRNA target sequence, whereas Cas9-DA resulted in single or double nucleotide editing of C to T conversions within the gRNA target sequence. These results suggest that the Cas9-DA approach may be useful for manipulating gene activity with decreased risks of genomic aberrations."
  • Implication of HpEts in gene regulatory networks responsible for specification of sea urchin skeletogenic primary mesenchyme cells[4] "The large micromeres of the 32-cell stage of sea urchin embryos are autonomously specified and differentiate into primary mesenchyme cells (PMCs), giving rise to the skeletogenic cells. We previously demonstrated that HpEts, an ets-related transcription factor, plays an essential role in the specification of PMCs in sea urchin embryos."
More recent papers  
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Search term: Sea Urchin Embryology

Older papers  
These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.

See also the Discussion Page for other references listed by year and References on this current page.

  • Dynamics of Delta/Notch signaling on endomesoderm segregation in the sea urchin embryo.[5] "Endomesoderm is the common progenitor of endoderm and mesoderm early in the development of many animals. In the sea urchin embryo, the Delta/Notch pathway is necessary for the diversification of this tissue, as are two early transcription factors, Gcm and FoxA, which are expressed in mesoderm and endoderm, respectively. Here, we provide a detailed lineage analysis of the cleavages leading to endomesoderm segregation, and examine the expression patterns and the regulatory relationships of three known regulators of this cell fate dichotomy in the context of the lineages."
  • The expression and distribution of Wnt and Wnt receptor mRNAs during early sea urchin development.[6] "In this study, we identified all Wnt and Wnt receptor mRNAs that are present in unfertilized sea urchin eggs and early embryos and analyzed their distributions along the primary (AV) axis. Our findings indicate that the asymmetric distribution of a maternal Wnt or Wnt receptor mRNA is unlikely to be a primary determinant of the polarized stabilization of beta-catenin along the AV axis. This contrasts sharply with findings in other organisms and points to remarkable evolutionary flexibility in the molecular mechanisms that underlie this otherwise very highly conserved patterning process."


<html5media height="300" width="280">File:Spermatozoa chemotaxis PMID23183693.mp4</html5media> Spermatozoa Chemotaxis

Sea urchin spermatozoa chemotaxis towards resact.[7] Resact causes stimulation of spermatozoa respiration and motility through intracellular alkalinization, transient elevations of cAMP, cGMP and calcium levels in sperm cells, and transient activation and subsequent inactivation of the membrane form of guanylate cyclase.

Spermatozoa chemotaxis icon.jpg
Sperm Chemotaxis
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Links: Hans Driesch | Movies


Sea Urchin-activinB.png

Sea Urchin- activin B expression

Sea Urchin- early embryo cleavage pattern.jpg

Sea Urchin- early embryo cleavage pattern

Sea urchin ectoderm patterning model 01.jpg

Sea urchin ectoderm patterning model

Early Development

Sea urchin SEM01.jpg

Sea urchin SEM02.jpg

Sea urchin SEM03.jpg

Endomesoderm Induction

Sea Urchin-endomesoderm induction.png

Sea Urchin-endomesoderm induction[8] Figure illustrates gene regulatory networks required for the early developmental process of endomesoderm induction.

Ectoderm Development

Sea urchin ectoderm patterning model.jpg

Changes in identity of ectodermal territories following perturbations of Nodal or BMP signaling and novel model of ectoderm patterning[9]

Schemes describing the morphology of control embryos and perturbed embryos.

(A) control embryo. The thick ciliated epithelium of the ciliary band is restricted to a belt of cells at the interface between the ventral and dorsal ectoderm.

(B) Nodal morphant. Most of the ectoderm differentiates into an expanded large ciliary band. An animal pole domain is nevertheless present in these embryos as shown by the presence of the apical tuft and at the molecular level by the expression of apical domain marker genes. In these embryos, the ectoderm surrounding the blastopore differentiates into dorsal ectoderm.

(C) embryo overexpressing Nodal. Most of the ectoderm differentiates into ventral ectoderm. A ciliary band-like ectoderm forms at the animal pole and in the ectoderm surrounding the blastopore.

(D) BMP2/4 morphants. An ectopic ciliary band forms in the dorsal ectoderm in addition to the normal ciliary band.

(E) bmp2/4 overexpressing embryo. All the ectoderm has a dorsal identity. The animal pole domain is largely absent. The triradiated stars represent the spicule rudiments.

(F) Proposed model for regionalization of the ectoderm of the sea urchin embryo through restriction of the ciliary band fate by Nodal and BMP signaling. Maternal factors such as SoxB1 promote the early expression of ciliary band genes within the ectoderm. Nodal signaling on the ventral side promotes differentiation of the ventral ectoderm and stomodeum and represses the ciliary band fate probably through the activity of Goosecoid as well as of additional repressors. Nodal induces its antagonist Lefty, which diffuses away from the ventral ectoderm up to the presumptive ciliary band territory. Within the ventral ectoderm, Nodal induces expression of bmp2/4 and of its antagonist chordin. Chordin prevents BMP signaling within the ventral ectoderm and probably within the presumptive ciliary band region. At blastula stages, protein complexes containing BMP2/4 and Chordin can diffuse towards the dorsal side to specify dorsal fates. In the dorsal ectoderm, BMP signaling strongly repress the ciliary band fate partly by inducing the expression of the irxA repressor. A high level of MAP kinase activity resulting from FGFA signaling in the lateral ectoderm likely contributes to maintain a low level of Nodal and BMP signaling within the presumptive ciliary band region by phosphorylating Smad1/5/8 and Smad2/3 in the linker region, which inhibits their activity. The presence of Chordin and Lefty in the prospective ciliary band allows expression of ciliary band genes to be maintained in this region. The ectoderm surrounding the blastopore differentiates into dorsal ectoderm likely because it receives Wnt signals that antagonize GSK3 and promote BMP signaling.

(G) In the absence of Nodal signaling, both the ventral and the dorsal inducing signals are not produced, ciliary band genes are not repressed and unrestricted MAP kinase signaling promotes differentiation of the ventral and dorsal ectoderm into neural ectoderm and ciliary band. The genes or proteins that are inactive are represented in light grey.

Wnt patterning

Sea urchin Wnt patterning model.jpg

Sea urchin Wnt patterning model[10]


Embryology History - Hans Driesch (1867 – 1941) was a German experimental embryology. From 1891 to 1901 he worked in Naples at the Marine Biological Station. His experimental work was designed to establish a formulation for development and ended by adopting an Aristotlean teleological theory of entelechy. Hans Driesch

Hans Driesch (1867 – 1941)

Embryology History - Hans Driesch manipulating blastomeres of sea urchin eggs. Hilfer1990 Fig05.jpg

Historic Images

Historic Disclaimer - information about historic embryology pages 
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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Bailey FR. and Miller AM. Text-Book of Embryology (1921) New York: William Wood and Co.


  1. Lillie FR. (1912). THE PRODUCTION OF SPERM ISO-AGGLUTININS BY OVA. Science , 36, 527-30. PMID: 17735765 DOI.
  2. Uchida A & Yajima M. (2018). An optogenetic approach to control protein localization during embryogenesis of the sea urchin. Dev. Biol. , 441, 19-30. PMID: 29958898 DOI.
  3. Shevidi S, Uchida A, Schudrowitz N, Wessel GM & Yajima M. (2017). Single nucleotide editing without DNA cleavage using CRISPR/Cas9-deaminase in the sea urchin embryo. Dev. Dyn. , 246, 1036-1046. PMID: 28857338 DOI.
  4. Yajima M, Umeda R, Fuchikami T, Kataoka M, Sakamoto N, Yamamoto T & Akasaka K. (2010). Implication of HpEts in gene regulatory networks responsible for specification of sea urchin skeletogenic primary mesenchyme cells. Zool. Sci. , 27, 638-46. PMID: 20695779 DOI.
  5. Croce JC & McClay DR. (2010). Dynamics of Delta/Notch signaling on endomesoderm segregation in the sea urchin embryo. Development , 137, 83-91. PMID: 20023163 DOI.
  6. Stamateris RE, Rafiq K & Ettensohn CA. (2010). The expression and distribution of Wnt and Wnt receptor mRNAs during early sea urchin development. Gene Expr. Patterns , 10, 60-4. PMID: 19853669 DOI.
  7. Kaupp UB. (2012). 100 years of sperm chemotaxis. J. Gen. Physiol. , 140, 583-6. PMID: 23183693 DOI.
  8. Sethi AJ, Angerer RC & Angerer LM. (2009). Gene regulatory network interactions in sea urchin endomesoderm induction. PLoS Biol. , 7, e1000029. PMID: 19192949 DOI.
  9. Saudemont A, Haillot E, Mekpoh F, Bessodes N, Quirin M, Lapraz F, Duboc V, Röttinger E, Range R, Oisel A, Besnardeau L, Wincker P & Lepage T. (2010). Ancestral regulatory circuits governing ectoderm patterning downstream of Nodal and BMP2/4 revealed by gene regulatory network analysis in an echinoderm. PLoS Genet. , 6, e1001259. PMID: 21203442 DOI.
  10. Range RC, Angerer RC & Angerer LM. (2013). Integration of canonical and noncanonical Wnt signaling pathways patterns the neuroectoderm along the anterior-posterior axis of sea urchin embryos. PLoS Biol. , 11, e1001467. PMID: 23335859 DOI.


Kominami T & Takata H. (2004). Gastrulation in the sea urchin embryo: a model system for analyzing the morphogenesis of a monolayered epithelium. Dev. Growth Differ. , 46, 309-26. PMID: 15367199 DOI.


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