The Ple142-lacZ transgene (bEMS86) was designed with the Ple142 MaxiPromoter (NR2E1-X; derived from the BAC RP11-144P8 that contains the whole (NR2E1) gene plus ~42 kb upstream and ~52 kb downstream, and also contains a portion of the SNX3 gene in the downstream sequence from the nuclear receptor subfamily 2, group E, member 1 (NR2E1) gene) upstream of a frt-flanked beta-galactosidase (lacZ) gene, an SV40 early polyA signal, and a human HPRT complementary sequence (containing exon1, intron1, exon2, and part of intron2). This construct was targeted as a single copy knockin to the Hprtb-m3 mutant locus on the X chromosome.