Fig. 1. openmind embryos exhibit diverse developmental defects by E9.25. A wild-type embryo at E9.25 (A) and an om homozygous littermate (B) of the same stage and size are shown in side views. The mandibular component of the first branchial arch is well developed in the wild type but is poorly developed in the om embryo (red arrowheads). The om heart is abnormally dilated and is near failure. (C) The anterior neural tube is fully closed by E9.25 in a normal embryo (shown in front view with tail removed), the heart is looped, and the optic vesicles are visible. (D) In the om mutant, the anterior neural tube fails to close and is abnormally thickened, the heart remains as an unlooped tube, and the optic vesicles are morphologically absent. (E) Wild-type somites are uniform, and the neural tube is smooth and straight at the midline in this dorsal view of the tail. (F) om somites are irregular in size (red arrowhead points to a small somite) and the neural tube is kinked.