ABSTRACT
Analysis of the distribution of the transcripts of given RAR isoforms by in situ hybridization has proven to be difficult because of the low sensitivity of the short discriminating probes However, Northern blot analyses have shown that all of the major RAR isoforms are expressed at various stages mouse development (37-39). In some cases this issue has also been addressed the generation of transgenic mouse lines bearing the LacZ reporter gene under the control of RAR [RARf3 P2 promoter (68,69); RAR~ Pl promoter (Mendelsohn et al., in preparation)]. These studies indicate that the specific spatiotemporal expression of the RAR~ gene corresponds to a transcriptional control of the Pl and P2 promoters, and also that the P2 promoter is inducible by RA in the animal (68,69).
