The Prp-TDP43A315Tinsertion site on MMU9. There are two closely linked transgene insertion sites on MMU9. These are Chr9:38,417,354 (insertion site 2, ‘ins2’) and Chr9:38,405,898 (insertion site 1, ‘ins1’) (MGSCv37, mm9), respectively. Similar to the insertion site for SOD1-G93A, these insertion sites are not within coding sequences, but are instead embedded in low complexity LINE elements. Moreover, these insertions are in close proximity to olfactory receptor genes, which share a high degree of sequence similarity and are known to evolve by tandem duplication (A). The orientation of the last copy of the transgene in the proximally inserted array and the truncated first copy of the transgene in the distally inserted array are shown in (B). Orientation of the chromosome is depicted proximal to distal (left to right) in both panels.