(A) Organization of the Nlrp1b duplicated exons 1 and 2 on chromosome 11 of CAST/EiJ and C57BL/6J mice and model of alternative splices . Arrangement of the duplicated exon 1 and 2 pairs encoding for different Nlrp1b variants on mouse chromosome 11. We propose the occurrence of two alternative splice variations. Splice event 1 (shown on left) results in a mature transcript encoding for Nlrp1b splice variant (SV) 1 and 2 in C57BL/6J and for SV3 in CAST/EiJ macrophages (in red). Splice event 2 (shown on right) results in a transcript encoding for Nlrp1b C57BL/6J SV3. In the CAST/EiJ genome, the SV3 sequence is present at this genomic location. The exact locations of the variants on chromosome 11 and GenBank accession numbers of described protein variants are given. Polymorphisms present in the variant proteins in comparison to the 129S1/SvlmJ protein sequence as outlined in Figure 3A are indicated by numbers. (B) Presence of Nlrp1b C57BL/6J splice variant (SV) 1 in the genome of diverse mice. The presence of exon 2 of Nlrp1b SV1 in the genome of mice harboring LT resistant (black) or sensitive (red) macrophages was analyzed. The upper panel shows the amplicons generated when specific primers were used to amplify Nlrp1b C57-SV1 or SV2, the middle panel shows genomic presence of sequences for all other variants, or of beta actin (control).