Biologically active kit ligand growth factor is produced by mouse Sertoli cells and is defective in SId mutant mice

In order to define the role of Kit ligand (KL) growth factor encoded at the mouse steel (SI) locus in spermatogenesis, we have examined its production in Sertoli cells. As a measure KL growth factor bioactivity, the ability to support proliferation and maintenance of mast cells was used in co-culture with primary mouse Sertoli cells. On the sertoli cells derived from +/+ and Wv/Wv mice, +/+ mast cells proliferated and were supported for more than 2 weeks, but not W/Wv mast cells. In contrast, Sertoli cells from SId/SId mice could not support +/+ mast cell proliferation under similar conditions. The supportive effect required close-range interaction of Sertoli cells with cultured mast cells. These results indicate that Sertoli cells derived from +/+ and Wv/Wv but not SId/SId mutant mice produce biologically active KL growth factor as a membrane-bound form. The biologically active KL of Sertoli cells may also play an important role in germ cell growth and differentiation.