Genetic Regulation of Wnt/PCP Components Through Fgf10/Fgfr2/Sox9 Module in Tear Duct Development.

PURPOSE: Tear duct obstruction can lead to a range of ocular surface disorders. Although Fgf signaling has been implicated in congenital tear duct obstruction, the associated signaling networks remain incompletely understood. To better elucidate the developmental biology and molecular genetics of the tear drainage system, we investigated genetic interactions between the Fgf and Wnt/planar cell polarity (PCP) pathways. METHODS: Mutant mice with disruptions of Fgf10, Fgfr2, or Sox9 were generated. Tear duct development was evaluated using immunohistochemistry and in situ hybridization with a set of molecular markers. Single-cell RNA sequencing combined with CUT&Tag analysis was used to define tear duct molecular identity and identify potential targets of the Fgf signaling pathway. A luciferase reporter assay and electrophoretic mobility shift assay (EMSA) were performed to validate Sox9 target genes. RESULTS: Fgf10 and Fgfr2 are required for tear duct formation by controlling the proliferation and survival of tear duct progenitors. The Fgf10/Fgfr2/Sox9 module genetically regulates a subset of Wnt/PCP genes involved in embryonic tear duct elongation. In particular, we show that Sox9 binds to and activates the promoter of Prickle1, a core Wnt/PCP component previously implicated in tear duct development. Finally, Fgf signaling appears to act unidirectionally on Wnt/PCP components, as neither Fgfr2 nor Sox9 expression is altered in Prickle1 mutants. CONCLUSIONS: This study uncovers a previously unrecognized direct genetic link between Fgf signaling and Wnt/PCP pathway in tear duct formation, suggesting that Wnt/PCP components may represent potential risk factors for congenital nasolacrimal duct obstruction (CNLDO), warranting further investigation.