The lps3 phenotype was identified in an ENU mutagenesis screen for mutants with impaired response to Toll-like receptor (TLR) ligands. The mutation is an A-to-T transversion at nucleotide position 2147 of the gene (Genbank Accession NM_021297) that results in replacement of aspartic acid by valine at amino acid position 709 of the receptor protein.