Fig. 1. The mol locus encodes Foxa2. (A-D) Lateral views of 36 hpf wild-type (A), mol^tv53a (B), mol^st20 (C) and foxa2 morphant (D) embryos. (E) Structure of the Foxa2 protein showing the positions of the likely truncations within the forkhead domain caused by the mol^tv53a and mol^st20 mutations. mol^tv53a results in the complete loss of transactivating domains II and III, leaving a C-terminally truncated Foxa2 protein. mol^st20 disrupts the forkhead box DNA-binding domain, downstream of mol^tv53a. Trans. domain, transactivating domain; fox domain, forkhead box DNA-binding domain. (F-H) Dorsal views of brains of a wild-type (F) and two mol^tv53a mutant (G,H) embryos labelled to reveal the cranial motor nuclei. The fusion of the facial motor nucleus (black arrowheads) is rescued in the mol^tv53a embryo expressing functional Foxa2 (H). The embryo in H is a homozygous mol^tv53a mutant as it still shows midline fusion of a reduced oculomotor nucleus (red arrowhead).