Developmental expression of functional cyclooxygenases in zebrafish

Area of Science:

• Molecular Biology
• Developmental Biology
• Pharmacology

Background:

• Cyclooxygenase (COX) research is limited by COX-2's role in mammalian reproduction and organogenesis.
• Zebrafish (Danio rerio) present a potential model system to overcome these limitations.
• Understanding COX function is vital for developmental and physiological processes.

Purpose of the Study:

• To characterize cyclooxygenase (COX) expression and function in zebrafish.
• To compare zebrafish COX isoforms (zCOX-1 and zCOX-2) with their mammalian orthologs.
• To establish zebrafish as a model for studying COX biology.

Main Methods:

• Cloning of full-length zebrafish COX-1 and COX-2 cDNAs.
• Chromosomal assignment of zCOX genes.
• Mass spectrometry for prostaglandin product identification.
• Pharmacological inhibition studies using selective inhibitors.
• Gene knockdown experiments (morpholino) to assess functional roles.
• Whole-mount in situ hybridization for expression pattern analysis.

Main Results:

• Zebrafish COX-1 and COX-2 proteins show 67% homology to human orthologs.
• Prostaglandin E2 is the primary product of zebrafish COX activity.
• zCOX-1 inhibition affects zebrafish thrombocyte aggregation and hemostasis, while zCOX-2 inhibition does not.
• zCOX-1 and zCOX-2 are widely expressed during zebrafish development.
• zCOX-1 knockdown leads to growth arrest in early embryogenesis.
• zCOX-1 expression is prominent in embryonic vasculature; zCOX-2 has a more restricted pattern.

Conclusions:

• Zebrafish COX-1 and COX-2 isoforms are genetically and functionally homologous to mammalian orthologs.
• Zebrafish provide a tractable and valuable model system for investigating COX biology and its role in development.
• Differential roles of zCOX-1 and zCOX-2 in zebrafish physiology and development are highlighted.