Expression of Tamoxifen-Inducible CRE Recombinase in Lcn5-CreERT2 Transgenic Mouse Caput Epididymis

The epididymis, which connects the testis to vas deferens, plays a crucial role regulating sperm maturation and fertilization. Here, a tamoxifen-inducible CreER(T2) recombinase transgenic mouse was generated to study the function of genes in the caput epididymis using the Cre/LoxP system, which is driven by the 1.8-kb Lcn5 promoter (Lcn5-CreER(T2)). BothCRErecombinase and ERT2 mRNAwere specifically expressed in the caput epididymis, beginning at postnatal Day 30 and increasing thereafter. Crossing these Lcn5-CreER(T2) transgenic mice with Rosa26; mT/mG reporter mice, which express membrane-boundGFP(mGFP) only afterCREis active at its genetic locus, resulted in the presence of GFP only in the middle/distal caput epididymis after tamoxifen induction. Efficiency of the CRE recombinase production in the caput epididymis was dose-and time-dependent. These tamoxifen-inducible caput epididymis-specific CRE recombinase transgenic mice thus provides a simple approach to modulate epididymal principal cells in vivo, allowing for the genetic investigation of caput epididymis-specific gene functions during sperm maturation.