Target type: biologicalprocess
The establishment, maintenance and elaboration of a pattern along a line or a point in an embryo. [GOC:dph, GOC:go_curators, GOC:sdb_2009, GOC:tb]
Embryonic axis specification is a fundamental process in development that establishes the anterior-posterior (head-to-tail), dorsal-ventral (back-to-belly), and left-right axes of the embryo. This process ensures proper organization of tissues and organs within the developing organism. Here's a detailed description of the biological process:
**1. Anterior-Posterior Axis Specification:**
* **Maternal Determinants:** The egg cytoplasm contains maternally derived molecules, such as mRNA and proteins, that are asymmetrically distributed. These determinants influence the development of the anterior and posterior poles of the embryo.
* **Bicoid and Nanos:** In Drosophila, the bicoid gene product, a transcription factor, is concentrated at the anterior pole, while the nanos gene product, a translation repressor, is concentrated at the posterior pole. These gradients establish the anterior-posterior axis.
* **Gap Genes:** Gap genes, activated by bicoid and nanos, control the expression of pair-rule genes.
* **Pair-Rule Genes:** These genes define the segmentation pattern of the embryo, dividing it into repeating units.
* **Segment Polarity Genes:** Segment polarity genes further refine the segmentation pattern, ensuring the proper development of each segment.
**2. Dorsal-Ventral Axis Specification:**
* **Dorsal-Ventral Gradient:** A gradient of the signaling molecule, Dorsal, is established across the dorsal-ventral axis.
* **Dorsal-Ventral Gene Regulation:** Dorsal protein concentration influences the expression of genes that specify dorsal and ventral structures. High Dorsal levels specify ventral structures, while low levels specify dorsal structures.
**3. Left-Right Axis Specification:**
* **Nodal Flow:** In many vertebrates, the left-right axis is established by the movement of fluid within the node, a structure in the developing embryo. This fluid flow creates a leftward flow of signaling molecules.
* **Left-Right Asymmetry:** The leftward flow of signaling molecules activates the expression of genes that specify left-sided structures.
**4. Key Signaling Pathways:**
* **Wnt Pathway:** Involved in anterior-posterior axis specification and cell fate determination.
* **Hedgehog Pathway:** Important for segmentation and patterning along the anterior-posterior axis.
* **TGF-beta Superfamily:** Members of this family, such as Nodal and BMP, are involved in dorsal-ventral axis specification and cell fate determination.
**5. Importance of Axis Specification:**
* Proper axis specification is crucial for the correct development of the embryo.
* Defects in axis specification can lead to severe developmental abnormalities, such as missing or misplaced organs.
**6. Evolutionary Conservation:**
* The basic principles of axis specification are conserved across many species, indicating their importance in animal development.
**7. Further Research:**
* Research continues to investigate the molecular mechanisms underlying axis specification, with a focus on identifying new genes, signaling pathways, and regulatory networks.
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| Protein | Definition | Taxonomy |
|---|---|---|
| Catenin beta-1 | A catenin beta-1 that is encoded in the genome of human. [PRO:WCB, UniProtKB:P35222] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| salvin | salvin: a biocyclic diterpenoid; from sage and rosemary (Lamiaceae) | abietane diterpenoid; carbotricyclic compound; catechols; monocarboxylic acid | angiogenesis modulating agent; anti-inflammatory agent; antineoplastic agent; antioxidant; apoptosis inducer; food preservative; HIV protease inhibitor; plant metabolite |
| toxoflavin | toxoflavin : A pyrimidotriazine that is 1,6-dimethyl-1,5,6,7-tetrahydropyrimido[5,4-e][1,2,4]triazine with oxo groups at positions 5 and 7. toxoflavin: azapteridine antibiotic; structure | carbonyl compound; pyrimidotriazine | antibacterial agent; antineoplastic agent; apoptosis inducer; bacterial metabolite; toxin; virulence factor; Wnt signalling inhibitor |
| cercosporin | cercosporin : An organic heterohexacyclic compound that is perylo[1,12-def][1,3]dioxepine-6,11-dione substituted by hydroxy groups at positions 5 and 12, by methoxy groups at positions 7 and 10, and by 2-hydroxypropyl groups at positions 8 and 9 (the R,R-stereoisomer). It is a phytotoxin which was first isolated from the pathogenic soybean fungus, Cercospora kikuchii and later found in multiple members of the genus Cercospora. cercosporin: phyytotoxin from Cercospora beticola Sacc; posses photodynamic action on mice, bacteria & plants | ||
| LSM-42773 | aromatic ketone | ||
| etodolac, (-)-isomer | (R)-etodolac : The R-enantiomer of etodolac. It is inactive, in contrast to the enantiomer, (S)-etodolac, which is a preferential inhibitor of cyclo-oxygenase 2 and a non-steroidal anti-inflammatory. The racemate is commonly used for the treatment of rheumatoid arthritis and osteoarthritis, and for the alleviation of postoperative pain. | etodolac | |
| ucn 1028 c | calphostin C: structure given in first source; isolated from Cladosporium cladosporioides |