In nonneuronal cells, these molecular switches control distinct types of actin-based cell motility in response to extracellular cues. It is thought that association of GEF proteins with complexes that bind the cytoplasmic domains of cell surface receptors provides the necessary link between extracellular cues and GTPase activation.
Drosophila trio mediates the development of multiple embryonic axon pathways.
The MB phenotypes are attributed to alteration in the intrinsic nature of neurites, as revealed by clonal analyses. To explore the relationship between trio and Rac in Drosophila, the compound eye was used as an established system to test for genetic interactions in GTPase signaling pathways. Rac overexpression under the control of the eye-specific promoter GMR creates a mispatterened 'rough' eye in which individual ommatidia are misshapen. This is true for additional trio alleles. In contrast, overexpression of Rho also generates a rough eye, but this phenotype is not significantly altered by reduction in trio activity.