Résumé
The
Dlx genes are expressed in a coordinate manner, establishing proximal–distal polarity within the pharyngeal arches. In zebrafish,
dlx2a is expressed in the migrating cranial neural crest that contributes to the pharyngeal arches. Expression of
dlx2a in the arches is subsequently followed by overlapping expression of the physically linked
dlx1a gene, and of other paralogues that include
dlx5a/dlx6a and
dlx3b/dlx4b. To investigate the patterning and establishment of arch proximodistal polarity in zebrafish, we characterized the function of
dlx2a and
dlx1a, using antisense morpholino oligonucleotides (MOs). We show that embryos injected with
dlx1a and
dlx2a MOs exhibit reduced and dysmorphic arch cartilage elements. The combined loss of
dlx1a and
dlx2a causes severe arch cartilage dysmorphology, revealing a role for these genes in maturation and patterning of arch chondrogenesis. Knockdown of
dlx2a affects migrating neural crest cells as evidenced by reduced expression of
crestin, and
sox9a transcripts, in addition to increased levels of apoptosis. During pharyngogenesis, loss of
dlx2a results in aberrant
barx1 expression and the absence of
goosecoid transcripts in the dorsal region of the ceratohyal arch. Defects in the differentiation of ectomesenchymal derivatives, including sensory ganglia and cartilage elements, indicate a role for
dlx2a in specification and maintenance of cranial neural crest.