Fig. 1

Identification of SM22α-positive stromal cells in mouse ovary development. a Diagram for mammalian oocyte development within ovarian follicles. Shortly after birth, mouse germ cell cysts undergo programmed breakdown while single oocyte survive to form primordial follicles. As follicles grow, granulosa cells keep proliferating (one-layer to multi-layer) until fluid-filled cavities (the antrum) appear between the layers of somatic cells at later stage of follicle development. At the same time, stromal cells (not shown in the diagram) develop into mature stage to surround the layers of theca/granulosa cells. b, c SM22α stromal cells surround oocytes. DDX4 (DEAD-box helicase 4; also known as VASA) and stromal cell marker SM22α were used co-immunofluorescence in ovaries of newborn (D0; b) and 7-day-old (c; D7) WT mice. In newborn ovaries, stromal cells (green) were arranged in strips within the interval of germ cells (red). Stromal cells become mature and envelope layers of granulosa cells in advanced follicles. Scale bars 60 μm in ×10 images; 15 μm in ×40 images. OV ovary, OC oocyte, GC granulosa cell, SC stromal cell. Asterisks indicate the same oocyte in the merged panel