title: Analysis of human soft palate morphogenesis supports regional regulation of palatal fusion.
abstract: It is essential to complete palate closure at the correct time during fetal development, otherwise a serious malformation, cleft palate, will ensue. The steps in palate formation in humans take place between the 7th and 12th week and consist of outgrowth of palatal shelves from the paired maxillary prominences, reorientation of the shelves from vertical to horizontal, apposition of the medial surfaces, formation of a bilayered seam, degradation of the seam and bridging of mesenchyme. However, in the soft palate, the mechanism of closure is unclear. In previous studies it is possible to find support for both fusion and the alternative mechanism of merging. Here we densely sample the late embryonic-early fetal period between 54 and 74 days post-conception to determine the timing and mechanism of soft palate closure. We found the epithelial seam extends throughout the soft palates of 57-day specimens. Cytokeratin antibody staining detected the medial edge epithelium and distinguished clearly that cells in the midline retained their epithelial character. Compared with the hard palate, the epithelium is more rapidly degraded in the soft palate and only persists in the most posterior regions at 64 days. Our results are consistent with the soft palate following a developmentally more rapid program of fusion than the hard palate. Importantly, the two regions of the palate appear to be independently regulated and have their own internal clocks regulating the timing of seam removal. Considering data from human genetic and mouse studies, distinct anterior-posterior signaling mechanisms are likely to be at play in the human fetal palate.
authors: Faculty of Dentistry, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada.
authors: Adrian
authors: A
authors: Danescu
authors: Faculty of Dentistry, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada.
authors: Melanie
authors: M
authors: Mattson
authors: Faculty of Dentistry, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada.
authors: Carly
authors: C
authors: Dool
authors: Faculty of Dentistry, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada.
authors: Virginia M
authors: VM
authors: Diewert
authors: Faculty of Dentistry, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada.
authors: Joy M
authors: JM
authors: Richman
mesh_terms: D004848:Epithelium / Q000196:embryology; D005333:Fetus / Q000196:embryology*; D006801:Humans; D008648:Mesoderm / Q000196:embryology; D009024:Morphogenesis / Q000502:physiology*; D010160:Palate, Soft / Q000196:embryology*; D012189:Retrospective Studies
keywords: aponeurosis; craniofacial; hard palate; medial edge epithelium; palatal shelf; submucous cleft; tensor veli palatini; velopharyngeal