Fig. 3. Me31B forms a complex with Exu and Yps, and is concentrated in the sponge body. (A-C) A stage 6 egg chamber expressing GFP-Exu (green) was stained for Me31B (red). Me31B colocalizes with Exu. (D-F) A stage 6 egg chamber expressing GFP-Me31B (green) was stained for Exu (red). Exu is colocalized with GFP-Me31B. (G-I) Stage 4 and stage 5 egg chambers expressing GFP-Me31B were stained for Yps (red). Yps is colocalized with GFP-Me31B. Note that Yps is expressed extensively in follicle cells that surround germline cells. Hence, the antibody failed to permeate well into the interior of germline cells. (J) An immunoelectron-microgram of a section for Me31B. The section shown is the cytoplasm of a nurse cell in a stage 9 egg chamber. Me31B signals are enriched in a distinctive cytoplasmic region, which is not surrounded by membrane. We detected 390 signals for Me31B in 356 µm² areas in sections of nurse cell cytoplasm. Among these, 331 signals (84.9%) were in these distinctive regions, which occupied only 57 µm² (16%) in the sections. m, mitochondrion. (K) Interaction between Me31B and Exu-Yps complex. Me31B and Yps were immunoprecipitated from ovary extracts in the absence (left) or presence (right) of RNase. Immunoprecipitates were separated by SDS-PAGE, transferred to membrane, and probed with antibodies against Me31B, Yps and Exu. In the presence of RNase A, Me31B-Yps and Me31B-Exu coimmunoprecipitation is diminished (right). Scale bar: 50 µm in A-I; 200 nm in J.