May 2006
Volume 47, Issue 13
ARVO Annual Meeting Abstract  |   May 2006
Cryptic Cre Activity During Gametogenesis in Cre–loxP Transgenic Mouse Lines
Author Affiliations & Notes
  • D.Y. Weng
    Ophthalmology, University, Cincinnati, OH
  • Y. Hayashi
    Ophthalmology, University, Cincinnati, OH
  • C.–Y. Liu
    Ophthalmology, University, Cincinnati, OH
  • S. Schwemberger
    Research, Shriners Hospital for Children, Cincinnati, OH
  • G. Babcock
    Research, Shriners Hospital for Children, Cincinnati, OH
  • A. Kuan
    Developmental Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, OH
  • W.W. Y. Kao
    Ophthalmology, University, Cincinnati, OH
  • Footnotes
    Commercial Relationships  D.Y. Weng, None; Y. Hayashi, None; C. Liu, None; S. Schwemberger, None; G. Babcock, None; A. Kuan, None; W.W.Y. Kao, None.
  • Footnotes
    Support  NIH grant EY14207; RPB; OLERF
Investigative Ophthalmology & Visual Science May 2006, Vol.47, 1588. doi:
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      D.Y. Weng, Y. Hayashi, C.–Y. Liu, S. Schwemberger, G. Babcock, A. Kuan, W.W. Y. Kao; Cryptic Cre Activity During Gametogenesis in Cre–loxP Transgenic Mouse Lines . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1588.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : Cre–loxP strategy has been used as a method of conditional ablation of genes in a cell–type and/or tissue–specific manner. We have noticed uncharacteristic excision of floxed genes in offspring from breeding of Cre/floxed bitransgenic and wild type mice. Attempts were made to identify the chronology of this uncharacteristic gene ablation by cryptic Cre expression during maturation of germ cells.

Methods: : The bitransgenic Kera–Cre/ZEG, Krt12–Cre/ZEG and BF1–Cre/ZEG mice were cross bred with C57BL/6 and the pattern of EGFP expression was observed under a ZEISS fluorescent microscope. The expression of LacZ gene in the bitransgenic Kera–Cre/Rosa26R and Krt12–Cre/Rosa26R was also examined in the different tissues including brain, eye, and testis using whole mount X–gal staining. To evaluate whether cryptic Cre activity is general phenomenon, floxed Smad4 and Tbr2 were used to examine recombination using PCR. Isolation of spermatogenic cells of Kera–Cre/Smad4 mice using FACS was performed to further study recombination.

Results: : The first generation of bitransgenic Kera–Cre/ZEG mice showed tissue specific EGFP expression pattern in the corneal stroma and CA1, CA2 regions of the hippocampus. However, Kera–Cre/ZEG and Kera–Cre/Rosa26R were cross bred with C57BL/6, whole body green and blue mice were found in the offspring respectively, even when the Cre transgene was absent in the progeny. Cryptic Cre activity was transmitted 100% by the sperm, and around 30% by the oocytes. Whole mount X–gal staining showed that Cre expression begins at the primary spermatocytes and continues through spermatids. FACS analysis of testicular cells of Kera–Cre/Smad4 mice indicated that recombination occurred in the primary spermatocytes. This cryptic Cre activity not only observes in the Kera–Cre mice but also in the Krt12–Cre, and BF1–Cre.

Conclusions: : This is the first report showing that there is a cryptic Cre activity during gametogenesis in the Cre–loxP bitransgenic mice.

Keywords: transgenics/knock-outs • genetics • cornea: basic science 

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