Disentangling The Heterogeneity Of The Midfacial Epithelium To Elucidate The Pathogenesis Of Cleft Lip/Palate

Abstract

Craniofacial development results from a tightly regulated choreography involving patterning, morphogenesis, and growth of multiple embryonic tissues and cell types. Clefts of the lip and/or palate (CL/P) are maiming disruptions of facial shape and represent the most common human craniofacial birth defect. During mammalian facial development, the maxillary prominence extends medially to contact the two nasal prominences (medial and lateral) at a three‐way anatomical seam named lambdoidal junction (λ), wherein the three prominences coalesce. When fusion of the facial prominences is impaired, orofacial clefting ensues. We have previously reported an essential role for the cephalic epithelium at the λ to enable normal fusion of the murine embryonic facial prominences. Using the mouse as a model, I am currently studying the spatial and temporal characteristics of these epithelial subpopulations using single‐cell RNAseq (scRNAseq) on microdissected facial prominences prior and after fusion occurs. By this approach, I have identified the transcriptional profiles that characterize the different epithelial subpopulations at the λ. Employing different bioimaging and fate mapping techniques, I am characterizing the cell behaviors and trajectories of selected λ epithelial subpopulations. In parallel, I am also conducting these analyses directly comparing control and mutant mouse embryos obtained from available genetic mutant lines with orofacial clefting (Pbx1/2 compound mutants). These studies have identified key changes in both transcriptomic signatures and cell behaviors in mutant mouse embryos, providing a deeper understanding of the molecular mechanisms underlying the pathogenesis of CL/P. Altogether, these approaches are helping me to elucidate the spatiotemporal dynamics of the cell subpopulations that comprise the λ epithelium in vivo, and the perturbed landscapes that cause disfiguring anomalies of the facial anatomical features in mammals.Support or Funding InformationThis work was funded by the National Institute of Health [RO1 grant DE024745 to L.S] and by the American Association of Anatomists [Postdoctoral Fellowship to M.L.].