Genomic fragment (coordinates X:9245044..9248369 , release 6 genome) encompassing the amx transcription unit in which the amx coding region has been replaced by the Hsap\TM2D3 variant 1 coding sequence (derived from cDNA clone NM_078474), allowing expression of the human gene under the control of amx regulatory sequences. In addition, the Hsap\TM2D3 coding sequence has been mutated to carry the P155L variant that is associated with increased risk and earlier onset of late-onset Alzheimer's disease.