Fig. 1

ext2^-/- mutant displays severe tooth phenotype.

Ventral view of alizarin-red-stained craniofacial skeleton and teeth at 6 dpf (A, B) and dissected and flat mounted 5^th pharyngeal arches with teeth (A2, B2) reveals the presence on each pharyngeal arch of 3 teeth in siblings (A, A2) and only one misshapen tooth in ext2^-/- larvae (B, B2). Note that the rod shaped branchial arch 5 to which the teeth attach is also ossified. Arrows point incomplete ossification of the mutant tooth. Tooth phenotype consisting of one misshapen tooth was observed in all (n>500) analysed ext2^-/- embryos whereas heterozygote fish were indistinguishable from WT. Tooth lengths varies between 3V¹, 4V¹ and 5V¹ in siblings (P<0.003). Each of those teeth was significantly longer then dak-tooth (P<0.0001) (C). Tooth widths of 3V¹ and 5V¹ were similar between siblings, and both were significantly narrower than 4V¹ (D). ext2^-/--tooth was significantly broader than any of the siblings teeth (3V¹, P<0.0001; 4V¹, P = 0.023 and 5V¹, P = 0.0001) (D). White boxes, siblings; grey boxes, homozygote mutant. Scale bar = 0.1 mm.