Malformation of Tear Ducts Underlies the Epiphora and Precocious Eyelid Opening in Prickle 1 Mutant Mice: Genetic Implications for Tear Duct Genesis

PURPOSE: Obstruction of the tear drainage causes a range of ocular surface disorders. Hitherto, the genetics of tear duct development and obstruction has been scarcely explored, and related animal models are lacking. This study aims to study the potential role of the Wnt/PCP pathway mediated by Prickle 1 in tear duct development and diseases. METHODS: A severe hypomorphic Prickle 1 mutant was generated. Histology and immunohistochemistry were performed to compare wild type, Prickle 1 hypomorphic, and null mutant tear ducts. In situ hybridization was conducted to identify the signaling components in the developing tear ducts. Three-dimensional (3D) reconstruction was used to detect the human embryonic tear duct. RESULTS: Here, we report that a severe Prickle 1 hypomorph mouse line exhibited epiphora. This phenotype was due to the blockage of the tear drainage by incompletely formed nasolacrimal duct (NLD) and lacrimal canaliculi (LC), which also causes precocious eyelid opening. We observed a dose-dependent requirement of Prickle 1 for tear duct outgrowth. An investigation of the expression of Wnt/PCP core genes demonstrated a subset of PCP signaling components expressed in the developing tear duct. Furthermore, Prickle 1 is not required for the expression of Fgfr2/Fgf10 and p63 genes, which are associated with the NLD and LC hypoplasia in humans. Last, we showed that Prickle 1 expression in the developing tear drainage system is conserved between mice and humans. CONCLUSIONS: The study suggests that malformed tear ducts caused by disruption of Prickle 1 underlies the epiphora and precocious eyelid opening.