A de novo missense mutation in MPP2 confers an increased risk of Vogt–Koyanagi–Harada disease as shown by trio-based whole-exome sequencing

Vogt–Koyanagi–Harada(VKH)disease is a leading cause of blindness in young and middle-aged people.However,the etiology of VKH disease remains unclear.Here,we performed the first trio-based whole-exome sequencing study,which enrolled 25 VKH patients and 50 controls,followed by a study of 2081 VKH patients from a Han Chinese population to uncover detrimental mutations.A total of 15 de novo mutations in VKH patients were identified,with one of the most important being the membrane palmitoylated protein 2(MPP2)p.K315N(MPP2-N315)mutation.The MPP2-N315 mutation was highly deleterious according to bioinformatic predictions.Additionally,this mutation appears rare,being absent from the 1000 Genome Project and Genome Aggregation Database,and it is highly conserved in 10 species,including humans and mice.Subsequent studies showed that pathological phenotypes and retinal vascular leakage were aggravated in MPP2-N315 mutation knock-in or MPP2-N315 adeno-associated virus-treated mice with experimental autoimmune uveitis(EAU).In vitro,we used clustered regularly interspaced short palindromic repeats(CRISPR‒Cas9)gene editing technology to delete intrinsic MPP2 before overexpressing wild-type MPP2 or MPP2-N315.Levels of cytokines,such as IL-1β,IL-17E,and vascular endothelial growth factor A,were increased,and barrier function was destroyed in the MPP2-N315 mutant ARPE19 cells.Mechanistically,the MPP2-N315 mutation had a stronger ability to directly bind to ANXA2 than MPP2-K315,as shown by LC‒MS/MS and Co-IP,and resulted in activation of the ERK3/IL-17E pathway.Overall,our results demonstrated that the MPP2-K315N mutation may increase susceptibility to VKH disease.

FTO-mediated m6A modification alleviates autoimmune uveitis by regulating microglia phenotypes via the GPC4/TLR4/NF-κB signaling axis

Uveitis,a vision-threatening inflammatory disease worldwide,is closely related to resident microglia.Retinal microglia are the main immune effector cells with strong plasticity,but their role in uveitis remains unclear.N6-methyladenosine(m^(6)A)modification has been proven to be involved in the immune response.Therefore,we in this work aimed to identify the potentially crucial m^(6)A regulators of microglia in uveitis.Through the single-cell sequencing(scRNA-seq)analysis and experimental verification,we found a significant decrease in the expression of fat mass and obesity-associated protein(FTO)in retinal microglia of uveitis mice and human microglia clone 3(HMC3)cells with inflammation.Additionally,FTO knockdown was found to aggravate the secretion of inflammatory factors and the mobility/chemotaxis of microglia.Mechanistically,the RNA-seq data and rescue experiments showed that glypican 4(GPC4)was the target of FTO,which regulated microglial inflammation mediated by the TLR4/NF-κB pathway.Moreover,RNA stability assays indicated that GPC4 upregulation was mainly regulated by the downregulation of the m^(6)A“reader”YTH domain family protein 3(YTHDF3).Finally,the FTO inhibitor FB23-2 further exacerbated experimental autoimmune uveitis(EAU)inflammation by promoting the GPC4/TLR4/NF-κB signaling axis,and this could be attenuated by the TLR4 inhibitor TAK-242.Collectively,a decreased FTO could facilitate microglial inflammation in EAU,suggesting that the restoration or activation of FTO function may be a potential therapeutic strategy for uveitis.

The genetics of Behcet’s disease in a Chinese population

Behcet’s disease is defined as a multisystemic inflammatory disease.Although the precise pathogenesis and etiology is still a mystery,accumulating evidence shows that genetic variants of immune-related genes have a profound influence on the development of Behcet’s disease.To explore the genetic factors for Behcet’s disease,our group investigated the association of Behcet’s disease with multiple immune response genes and has identified multiple Behcet’s disease-related immunoregulatory pathways in the Chinese Han population.A large number of gene polymorphisms were studied including STAT4,IL23R,CD40,CCR1/CCR3,STAT3,OPN,IL17,JAK2,MCP-1,CTLA4,PD-1,PD-L1,PD-L2,TGRBR3,CCR6,PTPN22,FCRL3,IRF5,SUMO4 and UBAC2.Significant associations were found between Behcet’s disease and STAT4,IL23R,CD40,CCR1/CCR3,STAT3,MCP-1,TGFBR3,FCRL3,SUMO4,UBAC2.These genetic predisposition studies support an important role for both lymphocyte differentiation as well as ubiquitination pathways.These findings are helpful in elucidating the pathogenesis of Behcet’s disease and hopefully will allow the development of novel treatment regimes.