Spiny rat SRY lacks a long Q‐rich domain and is not stable in transgenic mice

Abstract

Background: Although Tokudaia muenninki has multiple extra copies of the Sry gene on the Y chromosome, loss of function of these sequences is indicated. To examine the Sry gene function for sex determining in T. muenninki, we screened a BAC library and identified a clone (SRY26) containing complete SRY coding and promoter sequences. Results: SRY26 showed high identity to mouse and rat SRY. In an in vitro reporter gene assay, SRY26 was unable to activate testis-specific enhancer of Sox9. Four lines of BAC transgenic mice carrying SRY26 were generated. Although the embryonic gonads of XX transgenic mice displayed sufficient expression levels of SRY26 mRNA, these mice exhibited normal female phenotypes in the external and internal genitalia, and up-regulation of Sox9 was not observed. Expression of the SRY26 protein was confirmed in primate-derived COS7 cells transfected with a SRY26 expression vector. However, the SRY26 protein was not expressed in the gonads of BAC transgenic mice. Conclusions: Overall, these results support a previous study demonstrated a long Q-rich domain plays essential roles in protein stabilization in mice. Therefore, the original aim of this study, to examine the function of the Sry gene of this species, was not achieved by creating TG mice. K E Y W O R D SBAC, neo-Y, transgenic mouse, Y chromosome

Unusual Mammalian Sex Determination Systems: A Cabinet of Curiosities

“…Similarly, most copies of Sry, found in around 70 copies along the Y chromosome, are non-functional. The most conserved copy, which shows transcriptional activity, was unable to cause testis development in Sry+ transgenic XX mice [122,123], casting doubt on its role as the initial switch for sex determination in this species. If Sry had lost its function, the Y chromosome of T. muenninki could meet the same fate as the Y of T. osimensis and T. tokunoshimensis.…”