This is an important issue for anyone involved in using murine models of retinal degeneration.  It turns out that contamination of Rd8 mutation in the B6 mice is more wide spread than the C57BL/6N mice.  Labs worldwide are going to have to reassess their data due to this mutation and all reviewers will ask about this in the immediate future.  The genotyping analysis of a variety of vendor lines is described in this paper by Mary J. Mattapallil, Eric F. Wawrousek, Chi-Chao Chan, Hui Zhao, Jayeeta Roychoudhury, Thomas A. Ferguson, and Rachel R. Caspi.  The take home message is that the rd8 mutation is in the C57BL/6N strain which is used worldwide to produce transgenic and knockout models.  The implications for non-vision labs are not as clear, but for vision labs, substantial disease can be present unrelated to another specific disease gene and will need to be accounted for.