Identification of the rat swh mutation. A, Fine mapping of swh (left) and physical mapping of swh (right). The swh genetically mapped to the most telomeric part of rat Chr17, 0.25-cM distal from D17Rat132 and D17Rat140. In the physical map, the swh locus is localized to a ~0.2-Mb region between D17Rat140 and the telomere. Both Ero1lb and Edaradd have been mapped within the swh locus. B, Sequence analysis of Edaradd gene of wild-type and swh/swh rats. In the genomic DNA of swh/swh rat, a C to T (red) transition is present in exon 6 of rat Edaradd gene. This changes proline to serine at codon 153 of the deduced EDARADD protein. Rat codon 153 corresponds to codon 156 of mouse EDARADD isoform 1 (NP_598398) and codon 153 human EDARADD isoform B (NP_542776). C, Amino-acid sequence alignment of a region of the EDARADD death domain from different species. The 153rd amino acid that is altered in swh/swh rat is highly conserved in the vertebrates.