In order to better understand Pax6 function I generated a novel tool – a ‘Pax6 reporter’ transgenic mouse that expresses GFP under the control of Pax6 regulatory elements. The transgenic mouse was generated from a modified yeast artificial chromosome (YAC) that contains the human PAX6 gene and has been previously demonstrated to rescue loss of endogenous Pax6 in Pax6^sey/sey mice. The key advantages of a YAC addition transgenic include that it is already known that Pax6 regulatory elements are present over a 200Kb region and inserting a reporter gene into the endogenous Pax6 would not be independent of the endogenous locus. An expression cassette encoding GFP and an IRES-neoR vector were inserted into the YAC in frame with the normal PAX6 translation start point in exon 4, preserving the rest of the PAX6 locus. This put GFP and neomycin under the control of the PAX6 regulatory elements.  The modified YAC was then injected into fertilised mouse oocytes to generate nine lines of transgenic mice. Once generated the expression pattern in each line was analysed at a range of developmental stages by imaging appropriate sections of agarose embedded mouse embryos. This confirmed that the expression was the same as the previously reported Pax6 expression pattern. In addition, the copy number and extent of the YAC incorporated in each of the nine lines was investigated.