[Prickle planar cell polarity protein 1 involved in the pathogenesis of skeletal class Ⅲ malocclusion]

Objective: To explore the mechanisms of prickle planar cell polarity protein 1 (PRICKLE1) involved in the occurrence of skeletal Class Ⅲ malocclusion. Methods: After extracting the genomic DNA of all family members of the skeletal Class Ⅲ malocclusion pedigree with maxillary hypoplasia collected in the Department of Orthodontics at the Affiliated Stomatological Hospital of Nanjing Medical University in October 2021, whole exome sequencing and Sanger sequencing were performed to screen pathogenic genes/mutation sites and validate the mutations. Jaw tissue was collected during the operation of orthognathic patients who were treated in the Department of Oral and Maxillofacial Surgery at the same hospital from October 2021 to December 2022. Following the extraction of human jaw bone marrow mesenchymal stem cells and transfection with overexpressing lentivirus (lentiviruses overexpressing the gene of interest served as the wild group, lentiviruses overexpressing mutation site served as the mutant group) and knockdown lentivirus (divided into knockdown group 1 and 2, with transfection interference negative lentiviruses as the control group). Various assays including real-time fluorescence quantitative PCR (RT-qPCR), Western blotting, proliferation and Transwell assays, alkaline phosphatase staining and alizarin red staining were performed. Construction of zebrafish animal model, morpholino oligonucleotide (MO) were injected to knock down the expression of prickle1a and prickle1b in zebrafish (co-knocking group), and the control group was injected with standardized MO as a reference. Transcriptome sequencing, enrichment analysis and co-expression analysis were performed on the zebrafish craniofacial tissues of the two groups. Results: Two patients of this family carried this mutation PRICKLE1 c.113C>T. The transfection experiments showed that compared with the wild group (relative expression of PRICKLE1 was 21.97±0.60), the relative expression of mutant group (5.05±0.05) was significantly reduced (P<0.05), and cell proliferation and migration ability significantly enhanced (P<0.05), and osteogenic differentiation ability was significantly reduced (P<0.05). Compared with the control group, the proliferation and migration ability of cells in the two knockdown groups were significantly enhanced (P<0.05), and the osteogenic differentiation ability was significantly reduced (P<0.05). Zebrafish model experiments showed the width of the ethmoid plate was significantly reduced in the co-knocking group (282.50±61.77, t=5.29, P<0.001) compared with the control group (338.80±24.92). Transcriptome data and enrichment analysis showed that the differentially expressed genes were significantly enriched in the mitogen-activated protein kinase (MAPK) signaling pathway after the simultaneous knockdown of prickle1a and prickle1b in zebrafish. Conclusions: PRICKLE1 c.113C>T mutation might suppress the osteoblastic differentiation ability of jaw bone marrow mesenchymal stem cells by downregulating the MAPK signaling pathway, thereby involving the development of skeletal Class Ⅲ malocclusion.