Regulator of the Hippo/SWH (Sav/Wts/Hpo) signaling pathway, a signaling pathway that plays a pivotal role in organ size control and tumor suppression by restricting proliferation and promoting apoptosis. The core of this pathway is composed of a kinase cascade wherein Hippo (Hpo), in complex with its regulatory protein Salvador (Sav), phosphorylates and activates Warts (Wts) in complex with its regulatory protein Mats, which in turn phosphorylates and inactivates the Yorkie (Yki) oncoprotein. Mer acts synergistically along with Ex and Kibra to regulate the Hippo signaling pathway. Interacts with Moe and arm at the adherens junction (PubMed:8666669). Forms a complex with Kibra and Ex (PubMed:20159598). Interacts (via FERM domain) with Sav (via FBM motif) (PubMed:20159598). Interacts with Schip1 (PubMed:26954546). Membrane-associated, adherens junctions and endocytic compartments. Cytoplasmic, punctate. Expressed predominantly in the germline. Expressed in the developing oocyte from stage 6 to the end of oogenesis and in the apical ends of follical cells from stage 10. Ubiquitous expression throughout embryogenesis with enhanced expression in mesoderm of early embryos and midgut of late embryos. In embryonic CNS, expression is seen in neuropil and developing brain and is enhanced in neuronal cell bodies. In embryonic PNS, expression is seen within the cell body. In third instar larvae, expression is uniform in the eye imaginal disk and is enhanced at the morphogenetic furrow. In pupal eyes, expression is seen in the cytoplasm of secondary and tertiary pigment cells, bristle precursor cells and rhabdomeres. Expressed maternally and zygotically in embryos.