USING RNAi TO STUDY MATERNAL GENE FUNCTION IN "NON-MODEL" NEMATODES

Mary K. Montgomery, Kelly Galey and Jeff Norman, Macalester College, St. Paul, MN 55105

We are interested in comparing the role of maternal factors in early pattern formation between C. elegans and related nematode species, including the closely related C. briggsae and more distantly related Cephalobus sp. We are especially interested in maternal genes involved in cell-cell interactions affecting cell fate, such as apx-1, which encodes the ligand for GLP-1 (a Notch homolog), and mediates signalling from the germline blastomere P2 to a somatic blastomere, ABp, in C. elegans. Whereas the division patterns and blastomere positions in the early C. briggsae embryo closely resemble those of C. elegans (e.g., P2 still contacts ABp in a similar manner), those inCephalobus are significantly different. Thus, we would like to know to what extent the mechanisms governing cell fate in the early embryo have been conserved (or altered) in nematode development. One approach we are using is to clone homologs of C. elegans maternal genes, such as those in the Notch signalling pathway, from C. briggsae and Cephalobus, and use the powerful tool of RNAiÝ to disrupt gene function of the homologs in these genetically less tractable species.

Although first demonstrated in C. elegans, because RNAi has proven effective in such phylogenetically diverse species as Drosophila, trypanosomes, and planaria, we believe RNAi might be useful to study gene function in many "non-model" organisms as well. We are also working on determining what percentage of sequence identity is needed between the exogenous dsRNA and the target endogenous message to achieve effective interference.

ÝRNA interference: introduction of homologous dsRNA to specifically target a gene's product, resulting in null and hypomorphic phenotypes (see Fire et al. 1998 Nature 391:806-11, Montgomery et al. 1998 PNAS 95: 15502-07, and for review Sharp 1999 Genes&Dev 13:139-41)