FGF 8 Mouse, 194 a.a.
Description
Mechanisms of Action
FGF 8 Mouse binds to fibroblast growth factor receptors (FGFRs), activating mitogen-activated protein kinase (MAPK) pathways to regulate:
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Cell Proliferation: Induces dose-dependent growth in mouse 3T3 fibroblasts (EC₅₀ ≤ 20 ng/ml; specific activity = 50,000 units/mg) .
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Embryonic Development: Essential for limb outgrowth, midbrain patterning, and GnRH neuron emergence .
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Disease Pathways: Promotes angiogenesis and androgen-independent tumor growth in mammary and prostate cancers .
Limb Development
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Conditional inactivation of Fgf8 in mouse forelimbs results in aplasia of the radius, first digit, and humerus due to disrupted apical ectodermal ridge (AER) signaling .
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Compensatory upregulation of Fgf4 occurs in AERs lacking Fgf8, but insufficient to rescue limb defects .
Neuroendocrine Regulation
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FGF8 signaling is required for gonadotropin-releasing hormone (GnRH) neuron development in the embryonic olfactory placode .
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Androgen receptor activation directly upregulates Fgf8 transcription via response elements in its promoter .
Research Applications
Homology and Cross-Species Relevance
Product Specs
Q&A
Q1: How does the recombinant FGF8 Mouse, 194 a.a. differ from endogenous FGF8 isoforms?
Answer:
The recombinant FGF8 Mouse, 194 a.a. is a non-glycosylated polypeptide produced in E. coli, with a molecular mass of 22.5 kDa. It lacks post-translational modifications present in endogenous FGF8 isoforms, which may influence receptor binding or stability. For example, endogenous FGF8 isoforms (e.g., FGF8a, FGF8b) differ in N-terminal sequences, affecting their subcellular localization and signaling efficiency . Researchers should validate whether the recombinant protein mimics the activity of specific endogenous isoforms in their experimental system.
Q2: What experimental approaches have been used to study FGF8's role in limb development?
Answer:
Conditional knockout models using Cre/loxP technology have been critical. For instance, Fgf8 inactivation in the forelimb apical ectodermal ridge (AER) via Prx1-Cre transgenic mice revealed:
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Aplasia of anterior forelimb elements (radius, first digit) due to failed mesenchymal survival .
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Incomplete penetrance of humerus formation, attributed to partial rescue by Fgf4 expression .
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Altered gene expression cascades: Reduced Shh and Bmp2, despite increased Fgf4 .
Key Methodological Insight: RNA in situ hybridization and lineage-tracing studies are essential for mapping FGF8-dependent signaling hierarchies .
Q3: How do researchers address embryonic lethality when studying FGF8 function?
Answer:
Allelic series strategies and conditional knockouts bypass germline lethality:
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Hypomorphic alleles: Insertion of loxP-flanked neo cassettes (e.g., Fgf8 neo.floxed) reduces but does not eliminate FGF8 activity, enabling analysis of dosage-sensitive phenotypes .
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Tissue-specific deletion: Fgf8 exon 2/3 excision in the AER (Prx1-Cre) or first branchial arch (Hoxa2-Cre) isolates its role in specific developmental regions .
Data Contradiction Example: Germline Fgf8 nulls die by E9.5 , while conditional mutants survive, enabling analysis of later developmental stages .
Q4: What intracellular pathways mediate FGF8's effects on cell proliferation and survival?
Answer:
FGF8 activates p38 MAPK and PI3K-Akt pathways to regulate:
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Cell cycle progression: p38 promotes G1/S transition, increasing proliferation in dental mesenchyme .
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Apoptosis inhibition: PI3K-Akt signaling blocks pro-apoptotic factors, enhancing survival in the developing tooth germ .
Dosage Dependency: Paradoxically, both excessive and insufficient FGF8 levels increase apoptosis in forebrain progenitors, suggesting a threshold-dependent survival pathway .
Q5: How does FGF8 interact with transcription factors like Engrailed and Gbx2?
Answer:
FGF8 regulates mid/hindbrain patterning through EN and GBX2:
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EN1/2 dependency: FGF8 induces Pax5 expression in midbrain explants, but this requires EN proteins for maintenance .
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GBX2 function:
Methodological Note: Gain-of-function (misexpression) and loss-of-function (knockout) studies are combined to resolve epistatic relationships .
Q6: How does FGF8 influence tooth growth rate and size?
Answer:
FGF8 in dental mesenchyme acts as a pacing factor:
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Accelerates cell cycle: p38 activation drives G1/S progression, slowing tooth development and increasing size .
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Apoptosis inhibition: PI3K-Akt signaling sustains mesenchymal cell populations, contributing to larger tooth dimensions .
Species Differences: Human FGF8 is more broadly expressed in tooth germs than in mice, suggesting divergent regulatory mechanisms .
Q7: What challenges arise when interpreting FGF8 dosage effects?
Answer:
Non-linear responses complicate interpretation:
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Forebrain apoptosis: Both Fgf8 null and overexpression mutants show increased apoptosis, while intermediate levels reduce it .
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Signaling thresholds: Exceeding or falling below a critical FGF8 concentration disrupts survival pathways, possibly via feedback inhibitors .
Solution: Use allelic series (e.g., hypomorphic vs. null alleles) to map dose-response curves in specific tissues .
Q8: Which FGF8 knockout models are most effective for studying developmental processes?
Advantage of Conditional Models: Enables tissue-specific analysis while avoiding embryonic lethality .
Q9: Why does FGF8 appear to have opposing roles in Shh regulation?
Answer:
Context-dependent effects:
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Forelimb AER: Fgf8 mutants show reduced Shh expression, indicating FGF8 is required for its maintenance .
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Tooth development: FGF8 activation sustains Shh signaling in dental epithelium, promoting tooth growth .
Resolution: FGF8's role in Shh regulation depends on spatiotemporal context and cellular crosstalk .
Q10: How can FGF8 be used to study human developmental syndromes?
Answer:
Mouse models of agnathia: Fgf8 conditional mutants lacking BA1-derived structures resemble human first arch syndromes. Key insights include:
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BA1 primordium specification: Proximal regions require FGF8, while distal regions depend on other signals .
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Therapeutic potential: Rescue experiments could test FGF8 supplementation for craniofacial defects .
Limitation: Human FGF8 expression patterns (e.g., persistent dental epithelial expression) differ from mice, necessitating cross-species validation .
Product Science Overview
FGF8 plays a crucial role in several developmental processes:
- Embryonic Development: It functions as an embryonic epithelial factor and is involved in midbrain and limb development, organogenesis, embryo gastrulation, and left-right axis determination .
- Tumor Growth and Angiogenesis: FGF8 supports androgen and anchorage-independent growth of mammary tumor cells. Overexpression of FGF8 has been linked to increased tumor growth and angiogenesis .
- Adult Expression: In adults, the expression of the FGF8 gene is primarily restricted to the testes and ovaries .
- Formulation: The lyophilized form of FGF8 is typically reconstituted in sterile water to a concentration of at least 100 µg/ml, which can then be further diluted for various applications .
- Stability: While stable at room temperature for up to three weeks, it is recommended to store the lyophilized form below -18°C. Once reconstituted, it should be stored at 4°C for short-term use (2-7 days) and below -18°C for long-term storage . To prevent degradation, it is advisable to add a carrier protein such as 0.1% human serum albumin (HSA) or bovine serum albumin (BSA) and avoid freeze-thaw cycles .
- Purity: The recombinant FGF8 is typically greater than 97% pure, as determined by SDS-PAGE analysis .
