Repression of reporter genes by the EGFP-neo knock-in sequence. (A) Activity of beta-geo [Gt(ROSA)26Sor] monitored by X-gal staining (blue). Testes were obtained at 5 wk after birth from Gt(ROSA)26Sor mice with either EGFP-neo or EGFP-Δneo, or without these sequences. Tissue sections were counterstained with nuclear fast red (red). Note that beta-geo is repressed only in the presence of neo at the knock-in locus and that the repression is observed in spermatocytes and spermatids, but not in spermatogonia or Sertoli cells (located in the periphery of seminiferous tubules). (B) qRT-PCR of beta-geo and EGFP mRNAs. Germ cells were isolated from Gt(ROSA)26Sor and Cag-EGFP mice with either EGFP-neo or EGFP-Δneo, or without these sequences. The level of beta-actin mRNA was used as a reference. Control (+/+) samples were obtained from the same litters. Error bars indicate the standard deviations (SDs) of five biological replicates.
