Redd1 is a novel marker of testis development but is not required for normal male reproduction

In an effort to identify novel candidate genes involved in testis determination, we previously used suppression subtraction hybridisation PCR on male and female whole embryonic (12.0-12.5 days post coitum) mouse gonads. One gene to emerge from our screen was Redd1. In the current study, we demonstrate by whole-mount in situ hybridisation that Redd1 is differentially expressed in the developing mouse gonad at the time of sex determination, with higher expression in testis than ovary. Furthermore, Redd1 expression was first detected as Sry expression peaks, immediately prior to morphological sex determination, suggesting a potential role for Redd1 during testis development. To determine the functional importance of this gene during testis development, we generated Redd1-deficient mice. Morphologically, Redd1-deficient mice were indistinguishable from control littermates and showed normal fertility. Our results show that Redd1 alone is not required for testis development or fertility in mice. The lack of a male reproductive phenotype in Redd1 mice may be due to functional compensation by the related gene Redd2.