The Ple24-lacZ transgene (pEMS1495) was designed with the 3813 bp Ple24 minipromoter (CCKBR-C; derived from a portion of the promoter of the CCKBR gene and two downstream putative regulatory elements from the Gastrin/cholecystokinin type B receptor (CCKBR) 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.