Study About Polymorphisms, Gene-gene Interaction Of Reelin Signaling Pathway Related Genes In Chinese Han Autistic Children Using DNAchip

Objective:(1) To explore the association of reelin-signaling-pathway-related-genes polymorphisms with autism in Chinese Han population.(2) To explore the relationship between the gene-gene interaction of reelin-signaling-pathway-related-genes and the susceptibility of autism in Chinese Han population.(3) To explore the relationship between reelin-signaling-pathway-related-genes polymorphisms and the clinical phenotype of autism in Chinese Han population.Methods:(1) Genome-wide SNP genotyping was performed using Illumina CNV 370-Duo chip in 455 autistic children fulfilled with DSM-IV-TR criteria for autistic disorder and in 97 healthy controls. SNP data of the six genes in reelin signaling pathway were combined with the corresponding data of additional 358 controls, which was selected randomly from the genetic resource of State Key Laboratory of Medical Genetic of China. Single marker case-control association analysis and haplotype case-control association analysis based on linkage disequilibrium were conducted using Haploview 4.1 software after the data was screened. The significance of results was corrected by permutation test (number of permutation=1000).(2) 48 SNPs in reeelin-signaling-pathway-related-genes were involved in the analysis of gene-gene interaction using strategy of TagSNP & Linkage Block. Multifactor dimensionality reduction (MDR) was used to detect gene-gene interaction in autistic individuals. Model with the highest CV consistency, the highest testing accuracy as well as the significant permutation test results was considered as the best interaction-model.(3) The present study excluded 15 autistic individuals with incomplete clinical data.440 patients were divided into regression subgroup (180) and non-regression subgroup (260) according to the presence or absence of regression, alternatively divided into challenging-behavior subgroup (177) and non-challenging-behavior subgroup (263) according to the presence or absence of challenging behaviors. Chi square test was used to compare the inter-group differences of genotypic and allelic distribution to detect the association between polymorphisms of 48 SNPs mentioned above and autistic clinical phenotypes.Results:(1) Single marker case-control analysis did not find significant association between all 99 SNPs of RELN with autism after the P value was corrected by permutation test (P>0.05). Haplotype case-control analysis revealed that frequency of AAGTATCATGGG and CTTAGCCG were significantly higher in control group than in autism group after the P value was corrected by permutation test (χ2=8.658,10.000 respectively; P=0.015,0.002 respectively).(2) Single marker case-control analysis did not find significant association between all 154 SNPs of DAB1 with autism after the P value was corrected by permutation test (P>0.05). Haplotype case-control analysis revealed that frequency of GGTTTGGCATTTC was significantly higher in autism group than in control group after the P value was corrected by permutation test (χ2=8.461,P=0.019).(3) There were no significant differences in allelic frequency and haplotypic frequency between autism group and control group in all SNPs of LRP8, VLDLR, FYN and CDK5 after the P value was corrected by permutation test (P>0.05).(4) MDR analysis revealed that the three-loci genotypic combination (rs1454627-rs6943822-rs722187) was the best gene-gene interaction model of reeelin-signaling-pathway-related-genes in the etiology of autism (CV consistency=9/10, testing accuracy=0.822, P<0.001).(5) Significant differences were found in genotypic and allelic distribution of rs 10487160 within RELN between the regression subgroup and non-regression subgroup (χ2=10.570,10.190 respectively; P=0.005,0.001 respectively), genotypic frequency of GG and allelic frequency of G in regression subgroup were significantly higher than in non-regression subgroup. Significant differences were found in genotypic and allelic distribution of rs12666897 within RELN between the two subgroups (χ2=6.019,4.874 respectively; P=0.049,0.027 respectively), genotypic frequency of AC and allelic frequency of C in regression subgroup were significantly higher than in non-regression subgroup.(6) Significant differences were found in genotypic and allelic distribution of rs17157128 within RELN between the challenging subgroup and non-challenging subgroup (χ2=9.165,4.472 respectively; P=0.010,0.034 respectively). Genotypic frequency of AA and allelic frequency of A in challenging subgroup were significantly higher than in non-challenging subgroup.(7) Significant differences were found in genotypic distribution of rs3131735 within DAB1 between the challenging subgroup and non-challenging subgroup (χ2=8.430, P=0.015). Genotypic frequency of AG in challenging subgroup were significantly higher than in non-challenging subgroup.(8) Significant differences were found in genotypic and allelic distribution of rs1288520 within LRP8 between the regression subgroup and non-regression subgroup (χ2=7.790,7.095 respectively; P=0.020,0.008 respectively). Genotypic frequency of GG and allelic frequency of G in regression subgroup were significantly higher than in non-regression subgroup. (9) Significant differences were found in genotypic and allelic distribution of rs 1454627 within VLDLR between the regression subgroup and non-regression subgroup (χ2=7.143,4.127 respectively; P=0.028,0.042 respectively). Genotypic frequency of TT and allelic frequency of T in regression subgroup were significantly higher than in non-regression subgroup.Conclusion:(1) RELN is not likely to be susceptibility gene of autism. On the contrary, the haplotypes of AAGTATCATGGG and CTTAGCCG may be protective factors for childhood autism in Chinese Han population.(2) There is a positive association between the DAB1 haplotype of GGTTTGGCATTTC and autism, which suggests that DAB1 may be one of the susceptibility genes of autism in Chinese Han population.(3) There are no association between polymorphisms of LRP8, VLDLR, FYN, CDK5 and the susceptibility of autism in Chinese Han population.(4) Gene-gene interaction of DAB1-RELN-VLDLR may be involved in the etiology of autism in Chinese Han population.(5) Polymorphisms of rs10487160 and rs12666897 within RELN are associated with regression phenotype in autistic individuals.(6) Polymorphisms of rs17157128 within RELN is associated with challenging behavior phenotype in autistic individuals.(7) Polymorphisms of rs3131735 within DAB1 is associated with challenging behavior phenotype in autistic individuals.(8) Polymorphisms of rs1288520 within LRP8 is associated with regression phenotype in autistic individuals.(9) Polymorphisms of rs1454627 within VLDLR is associated with regression phenotype in autistic individuals.