The Rhomboid family of proteins is made up of several widely conserved polytopic membrane serine proteases that play roles in growth and development. RHBDD1 is highly expressed in the testis and is involved in the cleavage of BIK, a proapoptotic member of the Bcl-2 family. Overexpression or suppression by RNAi of RHBDD1 in 293 cells will reduce or enhance BIK-mediated apoptosis, respectively, demonstrating that RHBDD1 modulates BIK-mediated apoptotic activity. In GC-1 cells, a spermatogonia cell line that can differentiate into spermatids within the seminiferous tubules, suppression of RHBDD1 expression by RNAi caused the cells to lose the ability to survive and differentiate in mouse seminiferous tubules, suggesting that RHBDD1 may be associated with mammalian spermatogenesis.