Analysis of post-meiotic expression of a partial Map2k7 knockout in mouse testis

Map2k7 (synonym Mkk7), a member of the JNK signaling cascade, shows different transcript isoforms in Mus musculus. In an earlier study we described the occurrence of different Map2k7 expression patterns in testes of Mus musculus subspecies. We have previously identified a newly evolved testis-specific transcript for the Map2k7 gene in the subspecies M. m. domesticus. Here, we identify a new post-meiotocally active promoter that drives this transcript. The new promoter was gained in the stem lineage of closely related mouse species but was secondarily lost in the subspecies M. m. musculus and M. m. castaneus. A single mutation can be correlated with its transcriptional activity in M. m. domesticus, and cell culture assays demonstrate the capability of this mutation to drive expression. A mouse knockout line in which the promoter region of the new transcript is deleted reveals a functional contribution of the newly evolved promoter to sperm motility and the spermatid transcriptome.