Evaluation of the 5 '-flanking regions of murine glutathione peroxidase five and cysteine-rich secretory protein-1 genes for directing transgene expression in mouse epididymis

Based on strong epididymal expression of the mouse glutathione peroxidase 5 (GPX5) and cysteine-rich secretory protein-1 (CRISP-1) genes, we evaluated whether the 5.0-kilobase (kb)-long GPX5 and 3.8-kb-long CRISP-1 gene 5'-fl anking regions could be used to target expression of genes of interest into the epididymis in transgenic mice. Of the two candidate promoters investig ated, the CRISP-1 promoter-driven enhanced green fluorescent protein (EGFP) reporter gene was highly expressed in the tubular compartment of the testi s in all stages of the seminiferous epithelial cycle between pachytene sper matocytes at stage VII to elongated spermatids at step 16. In contrast to C RISP-1, the 5.0-kb 5' region of the mouse GPX5 gene directed EGFP expressio n to the epididymis. In the various GPX5-EGFP mouse lines, strongest expres sion of EGFP mRNA was found in the epididymis, but low levels of reporter g ene mRNA were detected in several other tissues. Strong EGFP fluorescence w as found in the principal cells of the distal caput region of epididymis, a nd few fluorescent cells were also detected in the cauda region. No EGFP fl uorescence was detected in the corpus region or in the other tissues analyz ed. Hence, it is evident that the 5.0-kb 5' flanking region of GPX5 promote r is suitable for directing the expression of structural genes of interest into the caput epididymidis in transgenic mice.