Transcription of Gli3 in fetal and adult thymic subsets. (A) Transcription of Gli3 was assessed by quantitative real-time RT-PCR on RNAs prepared from DN1, DN2, DN3, DN4, and DP thymocyte populations sorted from E16.5 wild-type C57BL/6 fetal thymi. Levels of Gli3 transcription shown are relative to that observed in the DN1 population and normalized for HPRT mRNA content. Maximal expression was seen in the DN4 subset. (B) Transcription of Gli3 was assessed as in panel A on RNAs prepared from adult thymocyte populations sorted from wild-type C57BL/6 mice. Gli3 transcription is absent or below levels of detection in all adult thymocyte populations.