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Fig. 2
alx1 and alx3 function redundantly to control anterior neurocranium morphogenesis in zebrafish. Larvae derived from a cross between alx1;alx3/+ parents were fixed at 5 dpf. (A,B) Representative siblings with normal facial structures (A) and with aberrantly short neurocranium (asterisk) and abnormally protruding jaw cartilage (arrowhead; B). (C-F) Alcian Blue staining revealed EP anomalies that range from mild (reduced median ethmoid plate width in D), moderate (absent median and reduced lateral ethmoid plate in E), to severe (absent ethmoid plate in F). (G) Penetrance and severity of cartilage defects is increased in alx1;alx3 compared to alx1;alx3/+ embryos (two trials). (H-M) Embryos derived from wildtype, alx1, or alx1;alx3/+ parental crosses were fixed at 2 dpf and stained for col2a1a expression using whole-mount in situ hybridization. (H,H′) Normal col2a1a expression in a wildtype embryo. (I,I′) A truncated EP in an alx1;alx3 embryo (arrow). (J) Normal col2a1a expression in a wildtype embryo. (K) Normal ethmoid plate and reduced presumptive scleral staining (asterisk) in an alx1 mutant. (L) Hypoplastic ethmoid plate (arrow) and absent presumptive scleral staining (asterisk) in an alx1;alx3 mutant. ANC, anterior neurocranium; OV, optic vesicle; PA, pharyngeal arches; FB, fin bud; SC, sclera. M: 75% of the embryos derived from alx1;alx3/+ have aberrant ANC and reduced scleral precursors (**P=0.0097, ****P<0.0001, Fisher's exact test; two trials for wildtype and alx1;alx3/+, and one trial for alx1). Embryos in A,B, and H-I′ are shown in lateral views, anterior to the left. Embryos in J-L are shown in ventral views, anterior to the left.