Ubiquitous expression of Sry induces embryonic lethality related to suppression of Tie2/Tek expression

Sry (sex-determining region on the Y chromosome) is a mammalian sex-determining gene on the Y chromosome. In mice, the transient expression of Sry in supporting cell precursor cells between 10.5 and 12.5 days post-coitus (dpc) triggers the differentiation of Sertoli cells from granulosa cells. The importance of the strict regulation of Sry expression remains unknown. Thus, we attempted to produce a Sry ubiquitous-expressing transgenic (Tg) mouse in which foreign Sry is driven by the CAG (cytomegalovirus immediate-early enhancer, chicken beta-actin promoter, and the fusion intron of chicken beta-actin and rabbit beta-globin)-Sry gene for ubiquitous expressing Sry. A low rate (2/127) of Tg pups was observed, whereas the rate of early-stage transgenic embryos before birth was 19.2% (5/26). The Sry ubiquitous-expressing embryos showed abnormal development. The results suggest that ubiquitous expression of Sry exerts a negative effect on embryonic development. One of the two adult Tg mice showed low levels of Sry expression. The other Tg mouse showed high Sry transgene expression, but was mosaic for the transgene. Developmental analysis of transgenic F1 embryos produced from the mosaic Tg mouse revealed that ubiquitous expression of Sry had a lethal effect on embryonic development around 12.5 dpc. The histological data indicated that ubiquitous expression of Sry induced abnormal cardiovascular development, resulting in embryonic death. Enhanced expression of Sry suppressed endogenous Tie2/Tek (tyrosine kinase with Ig and EGF homology domains 2/tunica interna endothelial cell kinase) expression in Sry-transfected primary cultured cells from wild type embryonic hearts. The results indicate that the tissue-specific and stage-specific expression of Sry is essential for normal embryogenesis.