SPECC1L‐Deficient Cells Show Impaired Collective Cell Migration Attributes that are Rescued by Upregulation of PI3K‐AKT Pathway

Abstract

Clefts of the lip and/or palate (CL/P) are common anomalies that occur in 1/700 live births. Pathogenic SPECC1L variants identified in patients with rare atypical clefts and syndromic CL/P suggest the gene plays a primary role in face and palate development. Null mutants are lethal at embryonic day 9.5 with defective neural tube closure and cranial neural crest cell delamination. Hypomorphic Specc1lΔ200 mutants die perinatally, but do not show cleft palate. Specc1lnull/Δ200 compound mutants resulted in transient oral adhesions, subepidermal blebbing, and a delay in palate elevation. Palate development requires extensive mesenchymal remodeling especially during palatal shelf elevation. We posit that this remodeling involves collective cell migration (CCM) of neural crest derived palate mesenchymal cells. Live time‐lapse microscopy was performed to visualize in vitro wound‐repair assays with SPECC1L‐deficient U2OS osteosarcoma and primary mouse embryo palatal mesenchyme (MEPM) cells. SPECC1L‐deficient cells consistently showed delayed wound closure. Directional movement of neighboring cells is a hallmark of CCM. In wound‐repair assays, an increase in movement parallel to the direction of wound front propagation results can be measured as an attribute of CCM. Tracking of individual trajectories of SPECC1L deficient cells during wound‐repair indeed shows an increase in cell movement perpendicular to the direction of wound closure. This diminished directionality causes delayed wound closure even though cells are adequately motile. We previously demonstrated SPECC1L to be a novel regulator of PI3K‐AKT signaling, with in vitro and in vivo SPECC1L deficiency exhibiting reduced PI3K‐AKT signaling. Indeed, wound closure delay, and the underlying CCM defect, in SPECC1L‐deficient U2OS and MEPM cells can be rescued by activation of the PI3K‐AKT signaling pathway using 740 Y‐P small molecule activator. Our data are the first to show CCM attributes in MEPM cells, and propose that MEPM cells can be used to model mesenchymal remodeling during palatal shelf elevation. We also show a novel role for SPECC1L in CCM through modulation of P13K‐AKT signaling.Support or Funding InformationThis project was supported in part by the National Institutes of Health grants DE026172 (I.S.). Core support and pilot funding was also provided by National Institutes of Health Center of Biomedical Research Excellence (COBRE) grant (P20 GM104936), Kansas IDeA Network for Biomedical Research Excellence (INBRE) grant (P20 GM103418), and Kansas Intellectual and Developmental Disabilities Research Center (IDDRC) grant (P30 HD 002528).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.