(A) Maximum intensity projections from confocal Z-stacks of whole ovary/mesonephros complexes at E14.5, E16.5, E17.5, E18.5, and P5, immunostained for FOXL2 (cyan) and PAX8 (red), and counterstained with Hoechst nuclear dye (grayscale). Samples in the top row were imaged from the dorsal side and samples from the bottom row from the lateral side. Side panels in (A, E17.5) are close-ups of the three regions of the RO outlined at E17.5 (from top to bottom: EOR, CR, and IOR). (B) 3D models generated by isosurface segmentation of lightsheet images taken of whole ovaries at E14.5, E17.5, and P0 immunostained for FOXL2 (cyan) and PAX8 (Müllerian duct, green; and Rete ovarii, red). All samples were counterstained with Hoechst nuclear dye (grayscale). Top panels represent the dorsal view, middle panels represent the medial view, and small bottom panels illustrate ventral and lateral views of the same ovary. Yellow asterisks indicate the location of the infundibulum of the presumptive oviduct for reference. Compasses on the bottom left of each panel indicate the orientation of the ovary: ; D, dorsal; L, lateral; M, medial; V, ventral. (C) Lightsheet images of whole ovaries from 3-month-old mice immunostained for AMH (cyan) and PAX8 (red). The top panel shows the extended slice view of the native image, while the bottom panel illustrates the 3D surfaces of the RO (PAX8, red) and ovarian follicles (AMH, cyan) generated by isosurface segmentation of the same image. Images in the right panel are close-ups of the three regions of the RO in an adult ovary: top—EOR; middle—CR; bottom—IOR. CR, connecting rete; EOR, extraovarian rete; IOR, intraovarian rete; MD, Müllerian duct; Mn, mesonephros; MT, mesonephric tubules; Mv, mesovarium; OC, ovarian capsule; Ov, ovary; RO, rete ovarii; WD, Wolffian duct. Scale bars, 100 μm.