Fig. 4. TrkB is expressed in germ cells of ovaries both before and after follicle formation in the mouse. In situ hybridisation uses a probe that recognises truncated and full-length forms of TrkB, whereas immunocytochemistry is specific for full length TrkB. (A-D) In situ hybridisation. (A) Using antisense probe (staining is primarily in oogonia, arrowheads) and (B) sense probe on E16.5 ovaries. (C) Antisense probe (staining is primarily in oocytes, arrowheads) and (D) sense probe on P4 ovaries (D). (E-H) Immunocytochemistry. (E) On E16 ovary with primary antibody present and (F) negative control for E16 ovary with no primary antibody. There is little full-length TrkB present at E16, but some expression can be seen in oogonia. (G) P0 ovary with primary antibody present and (H) P0 ovary with no primary antibody (full-length TrkB is strongly expressed in oocytes). Scale bars: 20 µm in A-D; 50 µm in E-H.