DEFT, a Novel Death Effector Domain-Containing Molecule Predominantly Expressed in Testicular Germ Cells**This work was supported by NIH Grant HD-31566 and by NIH Training Grant HD7493 (to S.Y.H.). Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession number AF043733 and AF053362 for human and rat DEFT, respectively)

Apoptosis is a physiological process by which multicellular organisms eliminate unwanted cells. Death factors such as Fas ligand induce apoptosis by triggering a series of intracellular protein-protein interactions mediated by defined motifs found in the signaling molecules. One of these motifs is the death effector domain (DED), a stretch of about 80 amino acids that is shared by adaptors, regulators, and executors of the death factor pathway. We have identified the human and rat complementary DNAs encoding a novel protein termed DEFT (Death EFfector domain-containing Testicular molecule). The N-terminus of DEFT shows a high degree of homology to the DEDs found in FADD (an adaptor molecule) as well as procaspase-8/FLICE and procaspase-10/Mch4 (executors of the death program). Northern blot hybridization experiments have shown that the DEFT messenger RNA (mRNA) is expressed in a variety of human and rat tissues, with particularly abundant expression in the testis. In situ hybridization analysis further in...