Natural product discovery via chemical genetics in zebrafish

• Published in: Planta Medica
• Main Authors: Crawford, AD, Breyne, A, Oosterlynck, J, Maes, J, Dewaele, M, Ruzzene, M, Kamuhabwa, AR, Nshimo, CM, Mbwambo, ZH, Verbruggen, AM, Pinna, LA, Agostinis, P, Busson, R, Rozenski, J, Esguerra, CV, de Witte, PAM
• Format: Conference Proceeding
• Language: English; German
• Published: 28.08.2007
• ISSN: 0032-0943; 1439-0221
• DOI: 10.1055/s-2007-986711

Natural products represent a significant – and currently underexploited – source of chemical diversity for the discovery and development of novel pharmaceuticals. One of the remaining bottlenecks in natural product discovery is the limited availability of biomedically relevant assays for high-throughput screening and rapid, bioactivity-guided fractionation of extracts. Recently, zebrafish have emerged as an effective system for the systematic in vivo identification and validation of both drug targets and small molecules. We have used the advantages of zebrafish (including small size, optical transparency, rapid development, high fecundity, and high genetic, physiologic, and pharmacologic similarity with humans) to establish a powerful platform for the discovery of bioactive natural products. Using a zebrafish-based, chemical genetic assay for anti-angiogenic activity relying on a sub-effective dose of the VEGF receptor inhibitor SU5416, we screened extracts from a collection of East African medicinal plants. Two extracts were identified that potentiated SU5416 in a dose-dependent manner. Using zebrafish bioassay-guided HPTLC fractionation, we rapidly identified the respective bioactive compounds as emodin (a known inhibitor of the protein kinase CK2) and a rare abietane diterpenoid with no previously described bioactivity. Intruigingly, CK2 has recently been described as an important modulator of the PI3K/AKT/FOXO pathway, one of the two main routes for VEGF signaling. We also determined the abietane diterpenoid to diminish AKT phosphorylation and downstream signaling events. These results substantiate the ability of chemical genetic screening in zebrafish to efficiently identify drug-like, pathway-specific inhibitors, and introduce the zebrafish as a novel platform for microgram-scale, in vivo natural product discovery.