title: The cellular and molecular etiology of the craniofacial defects in the avian ciliopathic mutant talpid2.
abstract: talpid(2) is an avian autosomal recessive mutant with a myriad of congenital malformations, including polydactyly and facial clefting. Although phenotypically similar to talpid(3), talpid(2) has a distinct facial phenotype and an unknown cellular, molecular and genetic basis. We set out to determine the etiology of the craniofacial phenotype of this mutant. We confirmed that primary cilia were disrupted in talpid(2) mutants. Molecularly, we found disruptions in Hedgehog signaling. Post-translational processing of GLI2 and GLI3 was aberrant in the developing facial prominences. Although both GLI2 and GLI3 processing were disrupted in talpid(2) mutants, only GLI3 activator levels were significantly altered in the nucleus. Through additional fine mapping and whole-genome sequencing, we determined that the talpid(2) phenotype was linked to a 1.4 Mb region on GGA1q that contained the gene encoding the ciliary protein C2CD3. We cloned the avian ortholog of C2CD3 and found its expression was ubiquitous, but most robust in the developing limbs and facial prominences. Furthermore, we found that C2CD3 is localized proximal to the ciliary axoneme and is important for docking the mother centriole to the ciliary vesicle and cell membrane. Finally, we identified a 19 bp deletion in talpid(2) C2CD3 that produces a premature stop codon, and thus a truncated protein, as the likely causal allele for the phenotype. Together, these data provide insight into the cellular, molecular and genetic etiology of the talpid(2) phenotype. Our data suggest that, although the talpid(2) and talpid(3) mutations affect a common ciliogenesis pathway, they are caused by mutations in different ciliary proteins that result in differences in craniofacial phenotype.
authors: Division of Plastic Surgery, Department of Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA Division of Developmental Biology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA.
authors: Ching-Fang
authors: CF
authors: Chang
authors: Division of Plastic Surgery, Department of Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA Division of Developmental Biology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA.
authors: Elizabeth N
authors: EN
authors: Schock
authors: College of Agricultural and Environmental Sciences, Department of Animal Science, University of California Davis, Davis, CA 95616, USA.
authors: Elizabeth A
authors: EA
authors: O'Hare
authors: Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
authors: Jerry
authors: J
authors: Dodgson
authors: USDA Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA.
authors: Hans H
authors: HH
authors: Cheng
authors: Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors: William M
authors: WM
authors: Muir
authors: Center for Advanced Microscopy and Imaging, Miami University, Oxford, OH 45056, USA.
authors: Richard E
authors: RE
authors: Edelmann
authors: College of Agricultural and Environmental Sciences, Department of Animal Science, University of California Davis, Davis, CA 95616, USA.
authors: Mary E
authors: ME
authors: Delany
authors: Division of Plastic Surgery, Department of Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA Division of Developmental Biology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA samantha.brugmann@cchmc.org.
authors: Samantha A
authors: SA
authors: Brugmann
mesh_terms: D000483:Alleles; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus; D002502:Centrioles / Q000378:metabolism; D002642:Chick Embryo; D002874:Chromosome Mapping; D002923:Cilia / Q000378:metabolism; D018388:Codon, Terminator; D019465:Craniofacial Abnormalities / Q000235:genetics*; D005347:Fibroblasts / Q000378:metabolism; D053823:Hedgehog Proteins / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D006579:Heterozygote; D051741:Kruppel-Like Transcription Factors / Q000235:genetics*; D009154:Mutation; D010641:Phenotype; D011110:Polymorphism, Genetic; D011499:Protein Processing, Post-Translational; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D000075746:Zinc Finger Protein Gli2
chemical_list: D018388:Codon, Terminator; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; D000075746:Zinc Finger Protein Gli2
keywords: Chicken; Ciliopathies; Craniofacial; Gli processing; Hedgehog signaling; Primary cilia; talpid2