Fig. 7. Chick Hes5b and Id2 are repressed by activator and repressor forms of Phox2b and by expressing the native homeodomain. (A-D'') In situ hybridization with chick Hes5b (A'-D') and Id2 (A''-D'') probes at 24 h.a.e. of PHDVP16 (A-A''), PHDEnR (B-B''), PHD (C-C'') and SHDVP16 (D-D'') constructs. The extent of electroporation is shown by GFP fluorescence (C) or in situ hybridization with a GFP probe (all others). Both, Phox2b transcriptional activator (PHDVP16) or repressor (PHDEnR) forms repress chick Hes5b (A',B') and Id2 (A'',B''). The repressive activity is shared by the Phox2 HD (C',C'), but not by control constructs with the Siamois HD (SHDVP16) (D',D'').