Figure 1.

Schematic representation of expression of c-kit in mouse germ cells from fetus to 30 days postpartum. PGCs from 8.5–13 dpc express full-length Kit which is located on the membrane. From 13.5 dpc to 3 dpp, the PGCs lose Kit expression and turn into c-kit^- gonocytes which are arrested. At 3 dpp, the gonocytes start to proliferate into A_s and A_al Spg, which are undifferentiated without expressing Kit. Expression of c-kit is re-started at around 7 dpp when the A₁–B stage Spg appear. A truncated isoform of c-kit starts to be expressed (Tr-Kit) in the cytocol of the spermatocytes and is kept expressed in later stage germ cells (spermatocytes, spermatids and spermatozoa). Sertoli cells express Kitl from 8.5 dpc to 13.5 dpc and 6–10 dpp only. Entry of germ cells into meiosis occurs around 10 dpp. Expression of Kit and Kitl in the spermatogenic cells and Sertoli cells respectively is represented by the red color in the membrane, cytosol and nucleus.