This mutation was identified in a screen of G1 progeny of ENU mutagenized male mice for responses to Toll-like receptor- (TLR-) activating ligands. It is a C-to-A transversion in exon 4 which results in replacement of proline by threonine at amino acid 138 of the protein (P138T). Mutant mice produce no active TNF, either secreted or membrane-bound. (J:124642)