Genotype-phenotype analysis and functional study of three novel LRP6 variants in non-syndromic oligodontia

Yunyun YuanYa ZhaoLingqiang MengShuyun ZhenHui LiJiabao RenBeibei LiChenyun DouYan HouWenjing ChenJing ZhangYulin DingWenjing Shen^*

• Hebei Medical University, Shijiazhuang, China

Tooth agenesis (TA) is a common craniofacial malformation in humans, characterized by the absence of one or more permanent teeth. Recent studies have identified the low-density lipoprotein receptorrelated protein 6 (LRP6) gene as an autosomal dominant contributor to TA. Herein we aimed to identify novel LRP6 variants in patients with non-syndromic oligodontia (NSO) and perform functional analyses of these variants. Whole-exome sequencing revealed three novel LRP6 variations (NM_002336): a truncating variant [c.2182C>T (p.Arg728*)] and two missense variants [c.3773C>T (p.Thr1258Met) and c.1441C>T (p.Arg481Cys)]. Bioinformatics analyses predicted the pathogenicity of these LRP6 variants. Immunofluorescence characterization revealed that the missense variants exhibited subcellular localization patterns comparable to wild-type LRP6, with predominant distribution in the plasma membrane and cytoplasmic compartments. Western blot analysis revealed impaired β-catenin expression in cells harboring the LRP6 missense variants, suggesting compromised canonical WNT signaling pathway activity. Functional assessment using the TOP/FOP-Flash luciferase reporter system demonstrated significantly reduced TCF/LEF transcriptional activity associated with these variants, though statistical significance was exclusively observed for the Arg481Cys variant (P<0.05). Literature review identified 39 LRP6 variants associated with 52 NSO patients, revealing that mandibular second premolars were the most frequently affected teeth, while maxillary first molars were least likely to be affected.