Antisense RNA inhibition of shha, but not shhb, prevents the formation of mature teeth. Ventral views of the tooth-forming region of alizarin red stained 100 hpf embryos. Teeth develop normally in control morpholino injected embryos (A, left-side tooth shown in inset). Teeth are eliminated from shha MO injected embryos (B), but retained in embryos injected with an identical amount (12 ng) of the shhb morpholino (C). The combination of 6 ng shha MO with 18 ng shhb MO results in teeth forming closer to the midline and appearing slightly developmentally delayed but otherwise with normal morphology (D). Scale bar 100 μm.