Craniofacial development and gene expression in <i>pitx2^ex4/5</i> morphants.

<p>Developmental patterns of <i>foxd3</i>, <i>dlx2a</i> and <i>dlx4a</i>, and <i>Tg(fli1:gfp)</i> expression in <i>pitx2 ^ex4/5</i> embryos. In situ hybridization was performed with <i>foxd3</i>, <i>dlx2a</i>, <i>dlx4a</i> or <i>gfp</i>-specific antisense riboprobe in control (<b>A–P</b>) or morphant (<b>A′–P′</b>) zebrafish embryos. Please note similar expression patterns in migrating neural crest cells (<i>foxd3</i>) and pharyngeal arch primordial regions (<i>dlx2a</i>) at 24-hpf (arrows in control (<b>A–C</b>) and morphant (<b>A′–C′</b>) embryos). Starting at 32-hpf, expression of <i>dlx2a</i>, <i>dlx4a</i> and <i>Tg(fli1:gfp)</i> in the posterior arches appears to be reduced in <i>pitx2^ex4/5</i> fish (arrowheads in control (<b>D–G</b>) and morphant (<b>D′–G′</b>) embryos) while expression in the anterior arches (arrows in control (<b>D–G</b>) and morphant (<b>D′–G′</b>) embryos) is not significantly affected. In 48–72-hpf embryos, an increased expression of <i>dlx4a</i> in the anterior arches is detected (arrows in control (<b>H–N</b>) and morphant (<b>H′–N′</b>) embryos) while expression in the posterior arches remains reduced (arrowheads in control (<b>H–N</b>) and morphant (<b>H′–N′</b>) embryos); <i>dlx4a</i> expression around the oral cavity in 48-hpf embryos (arrow with asterisk in <b>K</b> and <b>K′</b>) as well as a frontward extension of the anterior arches at 72-hpf (arrows in <b>L–N</b> for controls and <b>L′–N′</b> for morphants) are not observed in <i>pitx2^ex4/5</i> fish. Analysis of sections at 72-hpf also shows broadened expression of <i>dlx4a</i> in the craniofacial region of morphant embryos (<b>O′, P′</b>) in comparison to controls (<b>O, P</b>).