April 2014
Volume 55, Issue 13
ARVO Annual Meeting Abstract  |   April 2014
Genetic background effect on eye phenotype of Le-Cre transgenic mice
Author Affiliations & Notes
  • Natalie Dora
    Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
  • J. Martin Collinson
    Institute of Medical Sciences, University of Aberdeen, Aberdeen, United Kingdom
  • Robert E Hill
    Medical Research Council Human Genetics Unit, Medical Research Council Institute of Genetics and Moleular Medicine, University of Edinburgh, Edinburgh, United Kingdom
  • John D West
    Centre for Integrative Physiology, School of Clinical Sciences, University of Edinburgh, Edinburgh, United Kingdom
  • Footnotes
    Commercial Relationships Natalie Dora, None; J. Martin Collinson, None; Robert Hill, None; John West, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 6400. doi:
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      Natalie Dora, J. Martin Collinson, Robert E Hill, John D West; Genetic background effect on eye phenotype of Le-Cre transgenic mice. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6400.

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

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Purpose: Le-Cre transgenic mice (Ashery-Padan et al 2000, Genes Dev 14:2701-11) express Cre-recombinase in the developing head surface ectoderm from Pax6-Le tissue-specific regulatory elements. They have been widely used in Cre-loxP experiments to delete floxed genes in the developing surface ectoderm. We planned to use Le-Cre mice to deplete Pax6 only in surface ectoderm derivatives and compare the corneal epithelial phenotype to our previous studies with Pax6+/- mice, where Pax6 is depleted globally. Our first hypothesis was that crossing the Le-Cre transgene to the CBA/Ca inbred strain would not compromise its action and use of the same genetic background would make direct comparisons with our previous studies of CBA/Ca-Pax6+/- mice more meaningful.

Methods: Hemizygous Le-Cre and heterozygous floxed Pax6fl/+ mice were each crossed to inbred CBA/Ca mice for several generations and then intercrossed to produce experimental Le-Cre;Pax6fl/+ mice and three control genotypes. A panel of phenotypic endpoints was investigated to determine the effects of tissue specific depletion of Pax6 on the eye phenotype.

Results: Preliminary results were promising and adult Le-Cre;Pax6fl/+ corneas were abnormal. Eyes were small, the corneal epithelium had fewer cell layers, goblet cells accumulated and Pax6 & K12 immunostaining levels were reduced. As expected, WT;Pax6fl/+, Le-Cre;WT and WT;WT controls were normal. We analysed controls at each generation and, after several CBA/Ca backcross generations, Le-Cre;WT controls also had abnormal eyes, with phenotypes similar to those caused by Pax6-depletion. We started to breed out the CBA/Ca background by crossing Le-Cre mice to the original FVB strain and the Le-Cre;WT phenotype began to normalise.

Conclusions: Eye abnormalities occur in some homozygous Le-Cre mice and genetic background affects penetrance (Robinson et al 2005, IOVS 46, E-abstr. 1885). Our study now shows that genetic background-dependent eye abnormalities can also occur in hemizygous Le-Cre mice. This may have significant implications for other studies. Offspring with deleted floxed alleles are analysed in most Le-Cre experiments but these are also hemizygous for Le-Cre and often on mixed genetic backgrounds. Furthermore, many published Cre-loxP studies give incomplete details about which controls are analysed. Our results highlight the importance of including all the relevant controls in Cre-loxP experiments.

Keywords: 740 transgenics/knock-outs • 539 genetics  

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