Alk8 is required for neural crest cell formation and development of pharyngeal arch cartilages

Abstract

The type I TGF␤ family member receptor alk8 acts in bone morphogenetic protein (BMP) signaling pathways to establish dorsoventral patterning in the early zebrafish embryo. Here, we present evidence that alk8 is required for neural crest cell (NCC) formation and that alk8 signaling gradients direct the proper patterning of premigratory NCCs. We extend our previous functional studies of alk8 to demonstrate that ectopic expression of constitutively active and dominant negative Alk8, consistently results in more medially or laterally positioned premigratory NCCs, respectively. We also demonstrate that patterning defects in premigratory NCCs, induced by alk8 misexpression, correlate with subsequent defects in NCC-derived pharyngeal arch cartilages. Furthermore, an anteroposterior effect is revealed, where overexpression of Alk8 more severely affects anterior arch cartilages and decreased Alk8 activity more severely affects posterior arch cartilage formation. Ectopic expression studies of alk8 are supported by analyses of zygotic and maternal-zygotic laf/alk8 mutants and of several BMP pathway mutants. Pharyngeal mesodermal and endodermal defects in laf/alk8 mutants suggest additional roles for alk8 in patterning of these tissues. Our results provide insight into alk8-mediated BMP signaling gradients and the establishment of premigratory NCC mediolateral positioning, and extend the model for BMP patterning of the neural crest to include that of NCC-derived pharyngeal arch cartilages. Developmental Dynamics 228:683-696, 2003.

Early, H+-V-ATPase-dependent proton flux is necessary for consistent left-right patterning of non-mammalian vertebrates

“…NHE3 constructs were injected into the vegetal hemisphere within 60 minutes of fertilization. Zebrafish embryo microinjection was performed as described previously (Payne-Ferreira and Yelick, 2003). Results of injections are reported as: % of otherwise normal embryos that were heterotaxic; sample size (n); % of injected embryos that died or were abnormal after gastrulation and not scored; and 2 and P values comparing treated with controls.…”

Early expression of the <i>tbx</i>22 gene in zebrafish influences positioning of pharyngeal arch cartilages

“…Wild type (mismatch MO injected), tbx22-2-MO and splice blocking MO injected embryos were stained at 6 dpf with alcian blue, which stains acid glycosaminoglycans present in cartilage [25]. Each injected larvae was analyzed for the presence/absence of individual pharyngeal cartilage elements as well as any deviations from normal patterning when compared with normal embryos.…”

“…WISH was performed as previously described [24], using a modification of published protocols [25]. Embryos were cleared in glycerol and photographed.…”

bmp2b and bmp4 are dispensable for zebrafish tooth development

“…That Bmp signaling is important in zebrafish tooth development is indicated by several lines of evidence. Mutations in the type I Bmp receptor alk8, as well as overexpression of constitutively active and dominant negative versions of the encoded protein, result in alterations of pharyngeal tooth number and/or shape (Payne et al, 2001;Payne-Ferreira and Yelick, 2003). Delay or arrest of tooth formation has also been reported for mutations in the BMP antagonist ogon and the ligand bmp7a (Yelick and Schilling, 2002;Payne-Ferreira and Yelick, 2003).…”

“…Mutations in the type I Bmp receptor alk8, as well as overexpression of constitutively active and dominant negative versions of the encoded protein, result in alterations of pharyngeal tooth number and/or shape (Payne et al, 2001;Payne-Ferreira and Yelick, 2003). Delay or arrest of tooth formation has also been reported for mutations in the BMP antagonist ogon and the ligand bmp7a (Yelick and Schilling, 2002;Payne-Ferreira and Yelick, 2003). Wise and Stock (2006) found bmp2a, bmp2b, and bmp4 to be expressed during initiation and/or morphogenesis stages of zebrafish pharyngeal teeth, and further suggested that loss of Bmp expression in the zebrafish lineage (cypriniform fishes) may have been responsible for evolutionary loss of their oral teeth.…”