GO:0035804 structural constituent of egg coat: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0035804 (structural constituent of egg coat) is a molecular function describing proteins that provide structural integrity to the specialized extracellular matrix surrounding the ovum [1, 3].
• Egg coat proteins, such as zona pellucida (ZP) domain-containing proteins, are essential for oogenesis, fertilization, and early development [2, 3].
• The egg coat is composed of glycoproteins that form a filamentous matrix, and its structural components vary across species, from fish to mammals [1, 6].
• These proteins often evolve rapidly, likely due to positive selection driven by species-specific fertilization.
• Studying egg coat structural constituents is crucial for understanding reproductive biology, infertility, and species evolution [4, 8].
• CRISPR-based models enable precise interrogation of egg coat gene function in oogenesis and fertilization [2, 3].
Description
The molecular function termed structural constituent of egg coat (GO:0035804) refers to the action of molecules that contribute to the structural integrity of the egg coat, a specialized extracellular matrix surrounding the ovum in animals [1, 3]. This function is essential for providing structural support and plays critical roles in oogenesis, fertilization, and early development [2, 3]. Egg coat proteins are characterized by the presence of zona pellucida (ZP) domains, which are conserved across diverse taxa, from cephalochordates to mammals. The egg coat serves as a physical barrier and a mediator of sperm-egg interactions, and its structural components are often species-specific [4, 6]. Understanding the molecular players and mechanisms underlying this function is fundamental for reproductive biology and evolutionary studies [6, 8].
structural constituent of egg coat At A Glance
| GO ID | GO:0035804 |
|---|---|
| GO term | structural constituent of egg coat |
| Ontology | molecular_function |
| Synonym | structural constituent of vitelline envelope; structural constituent of zona pellucida |
| Major function | Provides structural integrity to the egg coat, an extracellular matrix surrounding the ovum |
| Related processes | Oogenesis, fertilization, early development |
| Key protein domains | Zona pellucida (ZP) domain |
| Taxonomic distribution | Animals, from invertebrates to vertebrates |
What Is GO:0035804?
The structural constituent of egg coat is a molecular function where a protein or glycoprotein contributes to the physical integrity and architecture of the egg coat, a specialized extracellular matrix that surrounds the ovum. This function is defined by the Gene Ontology as the action of a molecule that provides structural support to the egg coat, which is essential for oogenesis, fertilization, and early development. Synonyms include structural constituent of vitelline envelope and structural constituent of zona pellucida.
Why Is structural constituent of egg coat Important in Cell Biology?
The structural constituent of egg coat function is fundamental to reproductive success because the egg coat is the first point of contact between sperm and egg and must maintain structural integrity to protect the ovum and mediate fertilization [4, 8]. Disruptions in egg coat proteins can lead to infertility or polyspermy, and because these proteins often evolve rapidly, they are key to understanding speciation and reproductive isolation. Moreover, egg coat components are studied as models for extracellular matrix assembly and as targets for contraceptive development [2, 4].
• Essential for oogenesis and proper egg development.
• Mediates sperm-egg recognition and binding during fertilization [4, 8].
• Provides a physical barrier to prevent polyspermy.
• Rapid evolution of egg coat proteins contributes to reproductive isolation and speciation.
• Mutations in egg coat genes are associated with female infertility.
• Serves as a model for studying extracellular matrix assembly and function.
• Target for non-hormonal contraceptive development.
• Important for aquaculture and conservation biology, as egg coat proteins affect fertilization success [1, 7].
• Involved in species-specific fertilization mechanisms.
• Provides insights into the evolution of sexual reproduction.
What Happens During structural constituent of egg coat?
Synthesis and Secretion of Egg Coat Proteins
In simple terms: Egg coat proteins are made inside the egg cell and then transported out to form a protective layer.
Egg coat proteins, such as those containing the zona pellucida (ZP) domain, are synthesized in the oocyte and secreted to assemble the extracellular matrix. In teleosts, oestradiol-17 beta induces the major vitelline envelope proteins in both sexes, indicating hormonal regulation of their production. These proteins are then transported to the oocyte surface where they assemble into the egg coat.
Assembly and Structural Integrity
In simple terms: The secreted proteins come together to build a tough, organized coat around the egg.
The egg coat is composed of a filamentous matrix of glycoproteins. In the Indian freshwater murrel, structural analysis revealed a complex organization of egg-envelope proteins. In abalone, rapidly evolving ZP domain proteins are a major component of the vitelline envelope, forming the structural framework. The assembly process involves non-covalent interactions and possibly disulfide bonds to create a stable structure.
Role in Fertilization
In simple terms: The egg coat helps sperm recognize and penetrate the egg, and then blocks additional sperm.
During fertilization, the egg coat mediates species-specific sperm binding. In Xenopus laevis, dicalcin, a ZP protein, regulates fertilization competence of the egg coat. The structural integrity of the coat is crucial for the acrosome reaction, as seen in starfish where the main saccharide chain of the acrosome reaction-inducing substance is part of the egg coat. After fertilization, the coat undergoes changes to prevent polyspermy.
Post-fertilization Modifications
In simple terms: After a sperm enters, the coat changes to block other sperm and protect the embryo.
Following fertilization, the egg coat is modified to establish a block to polyspermy. This involves the release of cortical granule contents that alter the coat's structure, making it impenetrable to additional sperm. The structural constituents of the egg coat are thus dynamically involved in early development.
Key Genes Involved in GO:0035804 structural constituent of egg coat
The following genes encode proteins that function as structural constituents of the egg coat, many of which contain zona pellucida (ZP) domains.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ZP1 | Forms the filamentous matrix of the zona pellucida | Mutations linked to female infertility; model for matrix assembly |
| ZP2 | Sperm-binding and structural component | Key for sperm-egg interaction; studied in fertilization |
| ZP3 | Primary sperm receptor and structural protein | Essential for acrosome reaction; target for contraceptives |
| ZP4 | Structural component of the zona pellucida | Involved in species-specific fertilization |
| ZPD | Zona pellucida domain-containing protein | Major component of vitelline envelope in abalone |
| Dicalcin | Zona pellucida protein regulating fertilization competence | Studied in Xenopus laevis for egg coat function |
| Vitelline envelope proteins | Major structural proteins in fish eggs | Induced by oestradiol; important in aquaculture |
| Choriogenin | Precursor of egg envelope proteins in fish | Hormonally regulated; model for estrogenic effects |
| ZP domain proteins in Branchiostoma | Structural components of egg coat in cephalochordates | Evolutionary studies of ZP domain proteins |
| Acrosome reaction-inducing substance | Saccharide chain involved in fertilization | Studied in starfish for acrosome reaction |
| Egg envelope proteins in Channa punctatus | Structural constituents of egg-envelope | Characterized for structural analysis |
| Jelly coat glycoproteins | Structural components of anuran egg jelly | Analyzed for oligosaccharide structure |
| ZP1 in mammals | Structural integrity of zona pellucida | Knockout models show infertility |
| ZP2 in mammals | Sperm binding and structural role | Point mutations affect fertilization |
| ZP3 in mammals | Sperm receptor and structural protein | Key for species-specific binding |
| ZP4 in mammals | Structural component | Evolutionary studies |
| Vitelline envelope proteins in teleosts | Structural components | Hormonal regulation studies |
| Egg coat proteins in abalone | Rapidly evolving structural proteins | Model for positive selection |
How Is structural constituent of egg coat Regulated?
The expression of egg coat structural constituents is regulated by hormones such as oestradiol-17 beta, which induces the major vitelline envelope proteins in teleosts. Additionally, the assembly and function of these proteins can be modulated by post-translational modifications, including glycosylation, as seen in the jelly coats of Bufo arenarum and the acrosome reaction-inducing substance of starfish. In Xenopus laevis, dicalcin regulates fertilization competence, suggesting a regulatory role in egg coat function.
structural constituent of egg coat and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ZP1 | Female infertility due to abnormal zona pellucida | Knockout mouse model |
| ZP2 | Infertility and polyspermy | Point mutation knock-in mouse |
| ZP3 | Infertility and sperm-egg binding defects | Overexpression in cell lines |
| ZP4 | Reproductive isolation | CRISPR knockout in zebrafish |
| Dicalcin | Fertilization competence | Xenopus laevis knockout |
Infertility and Reproductive Disorders
Mutations in genes encoding egg coat structural constituents, such as ZP1, ZP2, and ZP3, have been associated with female infertility in humans. For example, defects in ZP1 can lead to abnormal zona pellucida formation and empty follicle syndrome. Understanding these proteins is crucial for diagnosing and treating infertility.
Cancer and Ectopic Expression
Some egg coat proteins, particularly ZP domain-containing proteins, are ectopically expressed in certain cancers, where they may contribute to tumor cell adhesion and migration. However, direct evidence linking GO:0035804 to cancer is limited, and further research is needed.
Evolutionary and Species-Specific Fertilization
Rapid evolution of egg coat proteins can lead to reproductive isolation and speciation. Studies in abalone have shown that positive selection acts on ZP domain proteins, which may contribute to species-specific fertilization and hybrid incompatibility. This has implications for understanding biodiversity and conservation.
From structural constituent of egg coat-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the role of ZP1 in zona pellucida assembly? | ZP1 knockout mouse |
| How do point mutations in ZP2 affect sperm binding? | ZP2 point mutation knock-in mouse |
| Can overexpression of ZP3 rescue fertility defects? | ZP3 overexpression in transgenic mice |
| What is the function of dicalcin in fertilization? | Dicalcin knockout in Xenopus laevis |
| How do egg coat proteins evolve in teleosts? | CRISPR knockout in zebrafish |
| What is the structural role of ZP domain proteins in abalone? | Knock-in of tagged ZP proteins in abalone |
How to Study the structural constituent of egg coat Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Mass spectrometry | Protein identification and quantification | Proteomic characterization of egg coat |
| Electron microscopy | Ultrastructure of egg coat | Structural analysis |
| Glycan analysis | Carbohydrate structure | Jelly coat oligosaccharides |
| CRISPR knockout | Gene function | Dicalcin in Xenopus |
| Sperm-binding assay | Fertilization competence | ZP2 mutations |
| RNA-seq | Gene expression | Hormonal regulation |
| Western blot | Protein expression | Vitelline envelope proteins |
| Immunofluorescence | Protein localization | Egg coat assembly |
Proteomic Characterization
Proteomic approaches, such as mass spectrometry, are used to identify and quantify egg coat proteins. For example, proteomic characterization of ZP domain-containing proteins in the cephalochordate Branchiostoma belcheri revealed the composition of the egg coat. This method is essential for discovering novel structural constituents.
Structural Analysis
Structural analysis techniques, including electron microscopy and X-ray crystallography, provide insights into the architecture of egg coat proteins. The structural analysis of egg-envelope in Channa punctatus used microscopy to reveal the organization of the egg coat. Such methods help understand how proteins assemble into a functional matrix.
Glycan Analysis
Glycan analysis, such as reductive beta-elimination followed by mass spectrometry, is used to determine the carbohydrate structures of egg coat glycoproteins. This was applied to the jelly coats of Bufo arenarum and the acrosome reaction-inducing substance of starfish. Glycans are critical for fertilization events.
Genetic and Functional Assays
Genetic approaches, including CRISPR-Cas9 knockout and knock-in, are used to study the function of egg coat genes. For instance, knockout of dicalcin in Xenopus laevis revealed its role in fertilization competence. Functional assays, such as sperm-binding assays, measure the impact of mutations on fertilization.
How CRISPR Can Be Used to Study GO:0035804 structural constituent of egg coat
Knockout
CRISPR knockout is used to completely abolish the function of egg coat genes to study their role in oogenesis and fertilization. For example, knockout of dicalcin in Xenopus laevis demonstrated its requirement for fertilization competence. Knockout models help determine if a gene is essential for egg coat structural integrity.
Point Mutation
Point mutations can be introduced to mimic human disease variants or to study specific amino acid residues critical for protein function. For instance, point mutations in ZP2 can affect sperm binding without disrupting overall structure. This approach is valuable for understanding structure-function relationships.
Knock-in
Knock-in of tagged or reporter genes allows visualization and tracking of egg coat proteins in vivo. Tagged knock-in of ZP domain proteins in abalone can reveal their localization and dynamics during egg coat assembly. This method is also used to create disease models.
Overexpression
Overexpression of egg coat proteins can lead to excessive matrix deposition or rescue loss-of-function phenotypes. Overexpression of ZP3 in transgenic mice has been used to study its role in fertilization. This approach helps dissect dosage effects and dominant-negative interactions.
How EDITGENE Supports structural constituent of egg coat Research
Researchers studying structural constituent of egg coat-related genes often need to determine whether a candidate gene is causally involved in egg coat assembly, fertilization, or reproductive disease. EDITGENE provides comprehensive CRISPR-based services to accelerate this research, from gene knockout to precise point mutations and knock-in models.
Contact EDITGENE today to design your custom CRISPR model for structural constituent of egg coat research.
Frequently Asked Questions About structural constituent of egg coat
What is GO:0035804?
GO:0035804 is the Gene Ontology molecular function term for structural constituent of egg coat, describing proteins that provide structural integrity to the egg coat, an extracellular matrix surrounding the ovum [1, 3].
What genes are involved in structural constituent of egg coat?
Genes encoding zona pellucida (ZP) domain-containing proteins, such as ZP1, ZP2, ZP3, ZP4, and dicalcin, are key players in this function [2, 3, 6].
What is the egg coat made of?
The egg coat is primarily composed of glycoproteins, often containing ZP domains, which assemble into a filamentous matrix [1, 6].
How does the egg coat function in fertilization?
The egg coat mediates species-specific sperm binding and undergoes changes after fertilization to block polyspermy [4, 8].
What diseases are associated with egg coat proteins?
Mutations in egg coat genes like ZP1 and ZP2 can cause female infertility due to abnormal zona pellucida formation [2, 4].
Why do egg coat proteins evolve rapidly?
Rapid evolution of egg coat proteins is thought to be driven by positive selection for species-specific fertilization and reproductive isolation.
What model organisms are used to study egg coat function?
Common models include Xenopus laevis, zebrafish, abalone, and mouse, each offering unique advantages for genetic and biochemical studies [2, 6, 7].
How can CRISPR be used to study egg coat genes?
CRISPR can create knockout, point mutation, knock-in, and overexpression models to dissect the function of egg coat genes in vivo and in vitro [2, 4, 6].
What methods are used to analyze egg coat structure?
Proteomics, electron microscopy, glycan analysis, and X-ray crystallography are commonly used to study egg coat structure and composition [1, 3, 5].
Is the egg coat involved in non-mammalian species?
Yes, egg coat structural constituents are found across animals, from fish to amphibians to invertebrates, with variations in composition and function [1, 5, 7].
Conclusion
The molecular function structural constituent of egg coat (GO:0035804) is essential for the structural integrity of the egg coat, a specialized extracellular matrix that plays critical roles in oogenesis, fertilization, and early development. Research across diverse species has revealed a conserved yet rapidly evolving set of proteins, primarily containing ZP domains, that mediate sperm-egg interactions and block polyspermy. Understanding these proteins has implications for reproductive biology, infertility, and evolutionary studies. CRISPR-based models and advanced proteomic and structural methods continue to illuminate the mechanisms and regulation of this important function.
References
- 1. Vijay P et al.. 2020. Structural analysis and characterization of egg-envelope in the Indian freshwater murrel, Channa punctatus.. Fish Physiol Biochem 46(5):1847-1856 PMID: 32535727
- 2. Miwa N. 2015. Dicalcin, a zona pellucida protein that regulates fertilization competence of the egg coat in Xenopus laevis.. J Physiol Sci 65(6):507-14 PMID: 26420688
- 3. Xu Q et al.. 2012. Proteomic characterization and evolutionary analyses of zona pellucida domain-containing proteins in the egg coat of the cephalochordate, Branchiostoma belcheri.. BMC Evol Biol 12:239 PMID: 23216630
- 4. Podolsky RD. 2002. Fertilization ecology of egg coats: physical versus chemical contributions to fertilization success of free-spawned eggs.. J Exp Biol 205(Pt 11):1657-68 PMID: 12000810
- 5. Morelle W et al.. 1998. Structural analysis of oligosaccharide-alditols released by reductive beta-elimination from the jelly coats of the anuran Bufo arenarum.. Eur J Biochem 252(2):253-60 PMID: 9523696
- 6. Aagaard JE et al.. 2006. Rapidly evolving zona pellucida domain proteins are a major component of the vitelline envelope of abalone eggs.. Proc Natl Acad Sci U S A 103(46):17302-7 PMID: 17085584
- 7. Hyllner SJ et al.. 1991. Oestradiol-17 beta induces the major vitelline envelope proteins in both sexes in teleosts.. J Endocrinol 131(2):229-36 PMID: 1744570
- 8. Koyota S et al.. 1997. Structure of the main saccharide chain in the acrosome reaction-inducing substance of the starfish, Asterias amurensis.. J Biol Chem 272(16):10372-6 PMID: 9099675
