Tfap2a-dependent changes in mouse facial morphology result in clefting that can be ameliorated by a reduction in Fgf8 gene dosage.
Failure of facial prominence fusion causes cleft lip and palate (CL/P), a common human birth defect. Several potential mechanisms can be envisioned that would result in CL/P, including failure of prominence growth and/or alignment as well as a failure of fusion of the juxtaposed epithelial seams. Here, using geometric morphometrics, we analyzed facial outgrowth and shape change over time in a novel mouse model exhibiting fully penetrant bilateral CL/P. This robust model is based upon mutations in Tfap2a, the gene encoding transcription factor AP-2α, which has been implicated in both syndromic and non-syndromic human CL/P. Our findings indicate that aberrant morphology and subsequent misalignment of the facial prominences underlies the inability of the mutant prominences to fuse. Exencephaly also occured in some of the Tfap2a mutants and we observed additional morphometric differences that indicate an influence of neural tube closure defects on facial shape. Molecular analysis of the CL/P model indicates that Fgf signaling is misregulated in the face, and that reducing Fgf8 gene dosage can attenuate the clefting pathology by generating compensatory changes. Furthermore, mutations in either Tfap2a or Fgf8 increase variance in facial shape, but the combination of these mutations restores variance to normal levels. The alterations in variance provide a potential mechanistic link between clefting and the evolution and diversity of facial morphology. Overall, our findings suggest that CL/P can result from small gene-expression changes that alter the shape of the facial prominences and uncouple their coordinated morphogenesis, which is necessary for normal fusion.
Department of Craniofacial Biology, University of Colorado Denver, 12801 East 17th Avenue, Aurora, CO 80045, USA.
Rebecca M
RM
Green
Department of Craniofacial Biology, University of Colorado Denver, 12801 East 17th Avenue, Aurora, CO 80045, USA.
Weiguo
W
Feng
Department of Pharmacology, University of Colorado Denver, 12801 East 17th Avenue, Aurora, CO 80045, USA.
Tzulip
T
Phang
University of California San Francisco, Orthopaedic Trauma Institute, Department of Orthopaedic Surgery, San Francisco, CA 94110, USA.
Jennifer L
JL
Fish
Department of Craniofacial Biology, University of Colorado Denver, 12801 East 17th Avenue, Aurora, CO 80045, USA.
Hong
H
Li
Human Medical Genetics and Genomics Program, University of Colorado School of Medicine, 12800 East 17th Avenue, Aurora, CO 80045, USA.
Richard A
RA
Spritz
University of California San Francisco, Orthopaedic Trauma Institute, Department of Orthopaedic Surgery, San Francisco, CA 94110, USA.
Ralph S
RS
Marcucio
Department of Cell and Developmental Biology, University of Colorado Denver, 12801 East 17th Avenue, Aurora, CO 80045, USA.
Joan
J
Hooper
McCaig Institute for Bone and Joint Health, Department of Cell Biology & Anatomy, University of Calgary, 3280 Hospital Drive NW, Calgary, AB T2N3Z6, Canada.
Heather
H
Jamniczky
McCaig Institute for Bone and Joint Health, Department of Cell Biology & Anatomy, University of Calgary, 3280 Hospital Drive NW, Calgary, AB T2N3Z6, Canada. Alberta Children's Hospital Research Institute, University of Calgary, 3280 Hospital Drive NW, Calgary, AB T2N3Z6, Canada.
Benedikt
B
Hallgrímsson
Department of Craniofacial Biology, University of Colorado Denver, 12801 East 17th Avenue, Aurora, CO 80045, USA. Human Medical Genetics and Genomics Program, University of Colorado School of Medicine, 12800 East 17th Avenue, Aurora, CO 80045, USA. Department of Cell and Developmental Biology, University of Colorado Denver, 12801 East 17th Avenue, Aurora, CO 80045, USA. Trevor.Williams@ucdenver.edu.
Trevor
T
Williams
D000483:Alleles; D000818:Animals; D017209:Apoptosis; D001842:Bone and Bones / Q000473:pathology; D002356:Cartilage / Q000473:pathology; D049109:Cell Proliferation; D002971:Cleft Lip / Q000235:genetics*; D002972:Cleft Palate / Q000235:genetics*; D004195:Disease Models, Animal; D005145:Face / Q000473:pathology; D005260:Female; D051524:Fibroblast Growth Factor 8 / Q000235:genetics* / Q000378:metabolism; D018628:Gene Dosage; D020869:Gene Expression Profiling; D005838:Genotype; D006801:Humans; D017403:In Situ Hybridization; D051379:Mice; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D015398:Signal Transduction; D050656:Transcription Factor AP-2 / Q000235:genetics* / Q000378:metabolism
C496457:Fgf8 protein, mouse; D050656:Transcription Factor AP-2; D051524:Fibroblast Growth Factor 8
AP-2α; BOFS; Branchio-oculofacial syndrome; Cleft lip/palate; Craniofacial; Fgf signaling pathway; Geometric morphometrics; TFAP2A