Fig. 1

Schematic diagram of wild-type (WT) and mutant CRX proteins made by the indicated mouse models. The WT CRX protein shown on the top is 299 amino acids (A.A.) in length and contains the indicated DNA-binding and transactivation domains (indicated by bars above diagram) and several conserved motifs (marked by solid grey and black boxes). The substitution mutation R90W lies within the homeodomain and reduces DNA-binding [21]. The frameshift mutation E168d2 results in a C-terminus truncated CRX protein that retains DNA-binding capability but fails to activate transcription, and is, therefore, antimorphic [21]. The frameshift mutation G255d1 ‘Rip’ results in a non-homologous C-terminal extension (dark grey hashed box), creating an antimorphic protein that no longer binds DNA [24]. The phenotypes of heterozygous mice carrying each of these mutations are summarized in Table 1