DataSheet1_Evolution of a New Testis-Specific Functional Promoter Within the Highly Conserved Map2k7 Gene of the Mouse.xlsx

Map2k7 (synonym Mkk7) is a conserved regulatory kinase gene and a central component of the JNK signaling cascade with key functions during cellular differentiation. It shows complex transcription patterns, and different transcript isoforms are known in the mouse (Mus musculus). We have previously identified a newly evolved testis-specific transcript for the Map2k7 gene in the subspecies M. m. domesticus. Here, we identify the new promoter that drives this transcript and find that it codes for an open reading frame (ORF) of 50 amino acids. 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. Our data show that a new functional transcript (and possibly protein) can evolve within an otherwise highly conserved gene, supporting the notion of regulatory changes contributing to the emergence of evolutionary novelties.

Map2k7（别名Mkk7）是一类保守的调控激酶基因，同时是c-Jun氨基末端激酶（JNK）信号级联反应的核心组分，在细胞分化过程中发挥关键功能。该基因具有复杂的转录模式，目前已在小家鼠（Mus musculus）中发现多种不同的转录本异构体。我们此前曾在小家鼠domesticus亚种（M. m. domesticus）中鉴定出Map2k7基因的一个新演化得到的睾丸特异性转录本。本研究中，我们鉴定出驱动该转录本表达的全新启动子，并发现其编码一段长度为50个氨基酸的开放阅读框（ORF）。该新型启动子起源于近缘小鼠类群的干群谱系，但随后在小家鼠musculus亚种（M. m. musculus）和小家鼠castaneus亚种（M. m. castaneus）中发生了二次丢失。单个突变与小家鼠domesticus亚种中的该转录本转录活性显著相关，且细胞培养实验证实该突变具备驱动基因表达的能力。我们构建了删除该新型转录本启动子区域的小鼠敲除品系，实验结果显示，该新演化启动子对精子活力及精子细胞转录组具有功能性贡献。本研究数据表明，在原本高度保守的基因内部可演化出具备功能的新型转录本（乃至潜在的功能性蛋白），这一发现支持了“调控变化可推动进化新特征产生”的观点。