Expression of Wnt9b and activation of canonical Wnt signaling during midfacial morphogenesis in mice.
Cleft lip with or without cleft palate (CLP) is the most common craniofacial birth defect in humans. Recently, mutations in the WNT3 and Wnt9b genes, encoding two members of the Wnt family of signaling molecules, were found associated with CLP in human and mice, respectively. To investigate whether Wnt3 and Wnt9b directly regulate facial development, we analyzed their developmental expression patterns and found that both Wnt3 and Wnt9b are expressed in the facial ectoderm at critical stages of midfacial morphogenesis during mouse embryogenesis. Whereas Wnt3 mRNA is mainly expressed in the maxillary and medial nasal ectoderm, Wnt9b mRNA is expressed in maxillary, medial nasal, and lateral nasal ectoderm. During lip fusion, Wnt9b, but not Wnt3, is expressed in the epithelial seam between the fusing medial and lateral nasal processes. Furthermore, we found that expression of TOPGAL, a transgenic reporter of activation of canonical Wnt signaling pathway, is specifically activated in the distal regions of the medial nasal, lateral nasal, and maxillary processes prior to lip fusion. During lip fusion, the epithelial seam between the medial and lateral nasal processes as well as the facial mesenchyme directly beneath the fusing epithelia strongly expresses TOPGAL. These data, together with the CLP lip phenotype in WNT3-/- humans and Wnt9b-/- mutant mice, indicate that Wnt3 and Wnt9b signal through the canonical Wnt signaling pathway to regulate midfacial development and lip fusion.
Center for Oral Biology and Department of Biomedical Genetics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
Yu
Y
Lan
Rosemary C
RC
Ryan
Zunyi
Z
Zhang
Steven A
SA
Bullard
Jeffrey O
JO
Bush
Kathleen M
KM
Maltby
Andrew C
AC
Lidral
Rulang
R
Jiang
D000818:Animals; D002971:Cleft Lip / Q000196:embryology; D002972:Cleft Palate / Q000196:embryology; D006023:Glycoproteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D008046:Lip / Q000196:embryology*; D051379:Mice; D010641:Phenotype; D015398:Signal Transduction / Q000502:physiology*; D051153:Wnt Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D060508:Wnt3 Protein
D006023:Glycoproteins; C555507:WNT3 protein, human; D051153:Wnt Proteins; D060508:Wnt3 Protein; C555508:Wnt3 protein, mouse; C515303:Wnt9b protein, mouse