Gpr125 identifies myoepithelial progenitors at tips of lacrimal ducts and is essential for tear film

Gpr125, encoded by Adgra3 , is an orphan adhesion G-protein coupled receptor (aGPCR) implicated in modulating Wnt signaling and planar polarity. Here we establish both physiological and pathological roles for Gpr125. We show that mice lacking Gpr125 or its signaling domains display an ocular phenotype with many hallmarks of human dry eye syndrome. These include squinting, abnormal lacrimation, mucus accumulation, swollen eyelids and inflammatory infiltration of lacrimal and meibomian glands. Utilizing a Gpr125-β-gal reporter and scRNAseq, we identify Gpr125 expression in a discrete population of cells located at the tips of migrating embryonic lacrimal ducts. By lineage tracing we show these cells function as progenitors of the adult lacrimal myoepithelium. Beyond defining an essential role for Gpr125 in tear film and identifying its utility as a marker of lacrimal progenitors, this study implicates Gpr125 in the etiology of blepharitis and dry eye syndrome, and defines novel animal models of these common maladies.