Tumor necrosis factor receptor superfamily, member 11a (TNFRSF11A) gene organization, splice pattern, protein domain architecture and the positions of the primers used (arrowheads). On the top: the structure of the TNFRSF11A gene with the addition of the new exon 9a. Inside numbering represents exon length (nucleotides). Figure shows the exon organization of each alternative spliced isoform with a representative protein structure: (i) the wt TNFRSF11A (receptor activator of NF-kB, RANK), numbering in exon boundaries indicates amino acid residue at the splice junction, (ii) the 263-aa-residue-long RANK-a (TNFRSF11A_Δ9), encompassing SP, four extracellular TNFR repeats, TM, and 20 aa of intracellular tail (from exon 8), (iii) the 337-aa-residue-long RANK-b (TNFRSF11A_Δ8,9) encompassing SP (signal peptide), four extracellular tumor necrosis factor receptor (TNFR) repeats, transmembrane domain (TM) and 94 aa intracellular tail (from exon 10) and (iv) the 299-aa-residue-long RANK-c (TNFRSF11A_Δ7,8,9) encompassing SP, four extracellular TNFR repeats and 94 aa from exon 10. The arrows indicate the translation start site and the black circle represents a stop codon. The putative protein products of exons 8, 9 and 10 are depicted as a doted, vertically and horizontally lined box, respectively.