title: MEMO1 drives cranial endochondral ossification and palatogenesis.
abstract: The cranial base is a component of the neurocranium and has a central role in the structural integration of the face, brain and vertebral column. Consequently, alteration in the shape of the human cranial base has been intimately linked with primate evolution and defective development is associated with numerous human facial abnormalities. Here we describe a novel recessive mutant mouse strain that presented with a domed head and fully penetrant cleft secondary palate coupled with defects in the formation of the underlying cranial base. Mapping and non-complementation studies revealed a specific mutation in Memo1 - a gene originally associated with cell migration. Expression analysis of Memo1 identified robust expression in the perichondrium and periosteum of the developing cranial base, but only modest expression in the palatal shelves. Fittingly, although the palatal shelves failed to elevate in Memo1 mutants, expression changes were modest within the shelves themselves. In contrast, the cranial base, which forms via endochondral ossification had major reductions in the expression of genes responsible for bone formation, notably matrix metalloproteinases and markers of the osteoblast lineage, mirrored by an increase in markers of cartilage and extracellular matrix development. Concomitant with these changes, mutant cranial bases showed an increased zone of hypertrophic chondrocytes accompanied by a reduction in both vascular invasion and mineralization. Finally, neural crest cell-specific deletion of Memo1 caused a failure of anterior cranial base ossification indicating a cell autonomous role for MEMO1 in the development of these neural crest cell derived structures. However, palate formation was largely normal in these conditional mutants, suggesting a non-autonomous role for MEMO1 in palatal closure. Overall, these findings assign a new function to MEMO1 in driving endochondral ossification in the cranium, and also link abnormal development of the cranial base with more widespread effects on craniofacial shape relevant to human craniofacial dysmorphology.
authors.affiliation: Department of Craniofacial Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA. Electronic address: ERIC.VANOTTERLOO@ucdenver.edu.
authors.forename: Eric
authors.initials: E
authors.lastname: Van Otterloo
authors.affiliation: Department of Craniofacial Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
authors.forename: Weiguo
authors.initials: W
authors.lastname: Feng
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045, USA.
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Jones
authors.affiliation: Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland; University of Basel, CH-4002 Basel, Switzerland.
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Hynes
authors.affiliation: Department of Craniofacial Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Clouthier
authors.affiliation: Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Department of Pediatrics, University of Colorado Anschutz Medical Campus, Children's Hospital Colorado, Aurora, CO 80045, USA.
authors.forename: Lee
authors.initials: L
authors.lastname: Niswander
authors.affiliation: Department of Craniofacial Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Department of Pediatrics, University of Colorado Anschutz Medical Campus, Children's Hospital Colorado, Aurora, CO 80045, USA.
authors.forename: Trevor
authors.initials: T
authors.lastname: Williams
mesh_terms: D000818:Animals; D002356:Cartilage / Q000196:embryology / Q000473:pathology; D002972:Cleft Palate / Q000196:embryology / Q000235:genetics*; D005038:Ethylnitrosourea; D005091:Exons; D018507:Gene Expression Regulation, Developmental; D005808:Genes, Recessive; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D008297:Male; D008445:Maxillofacial Development / Q000502:physiology*; D008648:Mesoderm / Q000166:cytology / Q000196:embryology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D016296:Mutagenesis; D009432:Neural Crest / Q000166:cytology / Q000196:embryology; D010012:Osteogenesis / Q000502:physiology*; D010159:Palate / Q000196:embryology* / Q000378:metabolism / Q000473:pathology; D017354:Point Mutation; D019291:Skull Base / Q000196:embryology* / Q000378:metabolism / Q000473:pathology; D013045:Species Specificity
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C516959:Memo1 protein, mouse; D005038:Ethylnitrosourea
keywords: Cleft palate; Cranial base; Endochondral ossification; MEMO1; Neural crest; Palatogenesis