Abstract
Mutations in human TBX22 cause X-linked cleft palate with anklyoglossia syndrome. The two zebrafish tbx22 splice isoforms, tbx22-1 and tbx22-2, encode proteins of 444 and 400 amino acids, respectively. Zebrafish tbx22 mRNA expression mirrors mammalian TBX22 expression and is consistent with early patterning of the vertebrate face. In zebrafish, tbx22 mRNA is strongly expressed during early pharyngeal arch development in the ventral mesenchyme, and a later expression domain is found in ectomesenchymal cells underlying the stomodeum, a bilaminar epithelial structure demarcating the early forming mouth. Therefore, tbx22 is hypothesized to be involved in craniofacial development. The objective of this work is to characterize the role of tbx22 during craniofacial development in zebrafish. Tbx22 knockdown revealed that defects in tbx22 signaling cause mild clefting, joint defects and dorsoventral patterning defects in cartilages. Quantitative PCR and in situ analysis revealed that knockdown of tbx22 also causes a dramatic decrease in expression of osr1 and gdf5. Craniofacial patterning is dependent on proper signals from endoderm, mesoderm and ectoderm. The early influence of tbx22 on signals within the ventral mesenchyme impacts the domains of several key pharynx-geal arch signals, thereby helping to regulate proper patterning of the developing jaw.
Highlights
Craniofacial development relies on signals emanating from the endoderm, ectoderm and the brain
As the Cranial Neural Crest (CNC) cells migrate ventrally from the dorsal neural tube they are influenced by signals such as sonic hedgehog produced by the foregut endoderm [1], forebrain expression of FGF-R [2], and Bone Morphogenetic Protein (BMP) and Noggin influence skeletal formation [3,4]
In the present study we have examined the role of zebrafish tbx22 in craniofacial development
Summary
Craniofacial development relies on signals emanating from the endoderm, ectoderm and the brain. Within each pharyngeal arch there are dorsal and ventral components which are specified by additional signals such as those found in the endothelin (edn) pathway [3]. The regulation of these secreted signals is accomplished through a variety of transcription factors including members of the MSX, DLX, OSR and tbx families [5,6,7,8]. The T-box genes are an ancient family of transcription factors that are well conserved throughout all metazoans [9,10].
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