Mediator of localized membrane signals. Implicated in the regulation of lamellipodial dynamics. Negatively regulates cell adhesion. Interacts with EVL and VASP and targets them to the leading edge (PubMed:15469845). Interacts (via Ras associating and PH domains) with RAC1 (PubMed:18499456). Recruited to the membrane, via the PH domain, by the phosphoinositide, PI(3,4)P2. Colocalizes with ENAH/VASP at the tips of lamellipodia and filopodia. Also colocalizes with the pathogens, Vaccinia and Enteropathogenic E.coli (EPEC) at the interface between the pathogen and their actin. Isoform RMO1-RAPH1 is ubiquitously expressed with highest levels in brain, heart, ovary and developing embryo. Isoform RMO1 is widely expressed with highest levels in liver. Low expression in B-cells. Reduced expression in metastatic osteosarcomas compared to primary osteosarcoma tumors. Down-regulated in both breast (43% of tissue samples) and ovarian (25% of tissue samples) cancers. Belongs to the MRL family.