The transgene contains a patient-derived bacterial artificial chromosome (BAC) containing the human DMPK (dystrophia myotonica-protein kinase) gene including a CTG repeat expansion in the 3' untranslated region. The BAC also contains the neighboring human DNA regions including both DMWD and RSPH6A sequences as well as the distal region (exons 13-27) of SYMPK. The breakpoint between the human sequence of the DMPK gene and the mouse genome is about 530 bp after the end of the repeat: the polyA signal is therefore included in the DMPK transgene. The insertion of the transgene caused a 1.8 kb deletion in the mouse genome removing the Sptbn4 (spectrin beta, non-erythrocytic 4) gene. Founder 24 contains a 77 CTG repeat expansion. (J:101977)