Fig. 1. Whole-mount in situ hybridisation to show the distribution of deltaD transcripts. (A) 30% epiboly. deltaD is transcribed in the marginal zone (black arrowhead). (B) 70% epiboly. The shield region is devoid of transcripts (white arrow). (C) 95% epiboly. deltaD expression in a V-shaped expression domain (1) anteriorly, in two longitudinal stripes (IS) in the trunk region of the neural plate, and in one transverse, band-like domain (white arrowhead) in the hypoblast. (D) Tailbud stage embryo. Expression domains in the neural plate comprise two stripes in an intermediate position (IS) and two further lateral and caudal stripes (LS). deltaD is also expressed in the primordium of the trigeminal ganglion (asterisk) and in a horseshoe-like domain (2). (E) Two-somite stage embryo. Two medial stripes (MS) in the neural plate at the level of the trunk. In addition, two further expression domains (3 + 4) appear in the prospective brain region. (F) Five-somite stage embryo. Intermediate and lateral stripes are displaced due to neurulation movements. The white arrowhead indicates the presomitic expression band. (G) 12-somite stage embryo. In addition to presomitic bands (white arrowhead), the anterior halves of the somites contain deltaD transcripts (black arrows). (H) 20-somite stage embryo. Expression domain 2 has shifted to a new position, whereas expression domain 3 is still in place. In addition deltaD transcripts can be detected in the anlage of the epiphysis (E). The white arrowhead indicates the presomitic expression band.