PI3K-Akt Signaling Pathway Involvement In Hemifacial Microsomia By Inhibiting Bone Modeling

Purpose: Hemifacial microsomia is a congenital craniofacial malformation,mainly involving the mandible and many other facial organs,which usually results in intractable facial deformities and dysfunction.The pathogenesis mechanism remains undetermined.This study aims to further understand its genetic pathogeny and to explore the role of PI3 KAkt signaling pathway in hemifacial microsomia.Methods: Whole-exome sequencing was applied to 34 sporadic cases and two pairs of monozygotic twins discordant for hemifacial microsomia.Using human genome(hg19)as a reference,mutant genes were screened according to mutation frequency,gene function,and risk assessment.The sporadic cases were further analyzed by gene functional pathway analysis and the identical twins were compared between pairs.Based on literature reports,the PI3K-Akt signaling pathway was selected for subsequent functional verification.The effects and mechanism of inhibiting the PI3 KAkt signaling pathway to osteoclastogenesis of bone marrow-derived mononuclearmacrophages(BMMs)and osteogenesis of mouse embryonic osteoblast precursor cells(MC3T3-e1)were studied by the pan-PI3 K small molecular inhibitor LY3023414 and small interfering RNA(si RNA),respectively.LY3023414 was then injected to the unilateral mandible of mice to observe the effect of PI3K-Akt signaling pathway inhibition on bone modeling.Results: A total of 6104 rare and non-synonymous mutations were screened in 34 sporadic cases,and 24 common signaling pathway abnormalities were summarized.No positive results were found from the monozygotic twins discordant for hemifacial microsomia.Akt gene silencing downregulated osteogenesis and osteoclastogenesis;LY3023414 attenuated osteogenesis through PI3K/Akt/GSK3β/β-catenin pathway and suppressed osteoclast differentiation by PI3K/Akt/GSK3β/NFATc1;local injection of LY3023414 lead to unilateral mandibular hypoplasia in mice.Conclusion: Pathway analysis may be an effective method to find out the underlying genetic pathogeny in rare polygenic diseases like hemifacial microsomia.Our study confirmed that inhibition of PI3K-Akt signaling pathway can suppress bone modeling in vitro and in vivo,which may be a contributor towards hemifacial microsomia.