Genetic Association Between SHANK2 Polymorphisms And Susceptibility To Autism Spectrum Disorder

Autism spectrum disorder(ASD)is one of early-onset(before the age of three)neurodevelopmental disorders,the prevalence of ASD in males is 4-5 times as many as that in females.ASD is characterized by symptoms,such as repetitive and stereotyped behaviors,impairments in social interaction,and dysfunctions in communication.Moreover,ASD prevalence has been gradually increasing around the world during last decade.It was estimated by the American network for autism and developmental disorders,the prevalence of ASD aged 8 years has converted 6.7‰(2010)into 14.6‰(2012)in America.It was reported by Asia-pacific Journal of Psychiatry in 2013 that the prevalence of ASD was 2.8-29.5/10000.Nowadays,the etiology and pathological mechanism of ASD is still unknown.Existing genetic studies show that the abnormalities and dysfunctions in synapses are linked to ASD.SH3 and multiple ankyrin repeat domains protein 2(SHANK2)is a member of the family of scaffold protein(SHANKs),SHANKs were mainly expressed in postsynaptic density(PSD),and promoted the formation of synapses and maintained the balance of excitatory and inhibitory synapses,and were combined with other function protein.Associations between genetic mutations in SHANK2 and susceptibility to ASD in children have been identified.Mutations in SHANK2 in mice cause the substantial changes of behavioural phenotypes,such as repetitive routines,anxiety-like phenotypes,and altered social behavior,which are similar to those observed in the patients with ASD.However,associations between SNPs in SHANK2and ASD risk have been less investigated.There is no specific therapy for ASD and ASD patients have poor outcomes,it is urgent to explore the etiology of disease and analyze the pathogenic genes provided the prevention and intervention for ASD.Objective:To evaluate the association between SNPs of SHANK2 and ASD susceptibility.Methods:This is a case-control study,a total of 465 subjects were included,case subjects were 226 and control subjects were 239.Cases were from the second department of pediatrics of the first hospital in Jilin University and the Spring Rehabilitation hospital in Jilin Province.Controls were from the second department of pediatrics of the first hospital in Jilin University.Nine SHANK2 SNPs(rs76717360,rs11236697,rs74336682,rs77950809,rs17428526,rs35459123,rs75357229,rs61887413 and rs77716438)were genotyped by improved multiple ligase detection reaction(iMLDR).χ~2 test was used to determine whether the genotype distributions were in Hardy-Weinberg equilibrium(HWE).The linkage disequilibrium(LD)degree between the loci was calculated using Haploview 4.2 software.χ~2 test was used to analyze whether the genotype and allele frequency distributions were significant different between the control and case groups.The online SNPStats analysis program was used to analyze whether the nine SNPs polymorphisms were associated with ASD under five different genetic models,and the haplotypes of SHANK2 were associated with ASD susceptibility.Results:A total of 465 subjects,226 cases(188 males and 38 females)and 239 healthy controls(193 males and 46 females)were included in this study.The mean ages for two groups were both 4.00(3.00,5.00)years.No significant differences were found in gender and age distributions between the two groups(P>0.05);All the genotypic distributions of nine SNPs(rs76717360,rs11236697,rs74336682,rs77950809,rs17428526,rs35459123,rs75357229,rs61887413 and rs77716438)were in HWE(P>0.05);The allelic and genotypic frequencies of the nine SNPs in SHANK2 were not significantly different between controls and ASD patients(P>0.05);Under the genetic models,subjects carrying the mutant heterozygote of SNP rs76717360(genotype:CT)had a higher risk of developing ASD than those carrying wild-type homozygote for allele C and mutation homozygote for allele T(OR=1.93,95%CI:1.06-3.51,P=0.03).Subjects carrying the genotype CT+TT had a higher risk of developing ASD than those carrying CC(OR=1.86,95%CI:1.04-3.31,P=0.03).The optional inherited model of rs76717360 was overdominant model(CT vs.CC+TT,AIC=647.0).No association between the other eight SNPs polymorphisms and risk of ASD(P>0.05);We further investigated the associations of haplotypes among these adjacent SNPs with ASD risk.Compared with the wild-type haplotype C-T-A of the 3SNPs(rs76717360-rs11236697-rs74336682),the haplotype C-C-A and C-T-G were significantly associated with a high risk of ASD(OR=2.04,95%CI:1.03-4.07;OR=3.44,95%CI:1.40-8.44).The haplotype C-A-G and T-G-G of SNPs(rs11236697-rs74336682-rs77950809)significantly differed from the haplotype T-A-G for developing ASD(OR=2.17,95%CI:1.14-4.15;OR=3.81,95%CI:1.58-9.18).Compared with the wild-type haplotype C-T-A-G,the haplotype C-C-A-G of SNPs(rs76717360-rs11236697-rs74336682-rs77950809)and the haplotype C-T-G-G carried the variant allele of rs74336682(G)increased risk for developing ASD(OR=2.06,95%CI:1.03-4.11;OR=3.52,95%CI:1.43-8.67).Compared with the wild-type haplotype T-A-G-A of the 4 SNPs(rs11236697-rs74336682-rs77950809-rs17428526),the haplotype T-G-G-A enhanced risk for developing ASD(OR=3.52,95%CI:1.43-8.63).Haplotypes with≥5 SNPs containing rs11236697 and rs74336682(T+G)are associated with risk of ASD.5 SNPs(OR=3.33,95%CI:1.34-8.25;OR=3.41,95%CI:1.39-8.40),6 SNPs(OR=3.15,95%CI:1.25-7.95;OR=3.57,95%CI:1.34-9.50),7 SNPs(OR=3.34,95%CI:1.25-8.92),8 SNPs(OR=3.96,95%CI:1.03-15.17);9 SNPs(OR=3.95,95%CI:1.03-15.13).Conclusion:To sum up,the polymorphism of rs76717360 is associated with risk of ASD;The haplotype C-T-G-G-A-T-T-T-G of the nine SNPs was significantly associated with ASD risk;SHANK2 is a susceptibility gene for ASD in Chinese children.