Analysis Of The Allele Mutation At Autosomal STR Loci And The Application Of Indels Site In Parentage Testing In Fujian Han Population

Objective: Observed5453cases of Fujian Han population which STR loci typingresults were not rule out the parentage relationship, analyzed the laws of mutations andcalculated the paternity index to explore the affection on parentage testing resultdetermination from STR loci allele mutation; to explore the application value of InDelsin parentage testing.Method:(1) Applying four autosomal STR typing system (IdentifilerTM、Sinofiler、PowerPlex16、 PowerPlex21), screened cases including1～2non Mendelianinheritance STR loci, then confirmed mutations by typing additional STR loci. MadeStatistical analysis of mutation rate, analyzed the laws and characteristic, calculate thePI.(2) Based on the result of STR tying that were “support parentage”,“excludeparentage”,“mutation suspected”331cases were divided into3groups. UsingInvestigator DIPplex kit that produced by QIAGEN corporation to run the InDelssites typing. Compared the result of STR tying and InDels typing; statistic the numberof excluding sites; draw frequency distribution map and statistic the excluding rate ofeach30InDels sites.Result:(1) There were114times allele mutations of17STR loci confirmed from5453parentage testing cases. Statistic the mutation rate of each the17STR loci. Theaverage mutation rate were0.128%. Mutations rates among each loci showedsignificant difference (p<0.01). The mutation rate was increasing as the geometricmeans of the longest run of perfect repeats(LRPR) was increased．(2) Except one three-step mutation all the rest were one-step mutation. Therewere53gain mutations and47loss mutations, the differences between them were notsignificant (p>0.05).(3) There were92(80.7%) paternal,17(14.9%) maternal and5(4.38%) uncertain mutation were find. Paternal: maternal=5.41:1, the differences between themwere significant(p<0.01).(4) All the CPI of these cases>1; for trio, the CPI of27(32.53%) cases wereless than10000, the CPI of50%cases were between10000to100000; for diad, theCPI of11(39.29%) cases were less than10000.(5) Two allele dropout cases were confirmed in this research.(6) Clear typing result could be obtain with Investigator DIPplex systemrunning in genetic analyzer.30InDels sites typing result with5color markers wereacquired, in which could discrimination heterozygote and homozygote definitive.(7)30InDels sites of all the non Mendelian inheritance trio(or biad) include atleast2homozygote. All of the109“exclude” trios found non Mendelian inheritancesites. Among the100“exclude” biads, there had been find9cases with none of the30sites did not comply with the genetic rul. all the rest91“exclude” biads found nonMendelian inheritance sites.(8) With30InDels sites typing,1case were identified as “exclude” in the22“mutation suspected” group.Conclusion:(1) For Fujian Han population mutations rates among each loci showedsignificant difference; the mutation rates was positive correlated with the geometricmeans of LRPR; the probability of gain mutation and loss mutation were equal; thenumerical of paternal mutation were larger than maternal.(2) The statistic result of PI calculated with mutation rate acquired from thisresearch prompt that made parentage determination through15～20STR loci typinghas a certain risk in the situation considering mutation.(3) The found of allele dropout cases prompt that in the situation consideringmutation STR typing with renewing primer system should be done, when both theparental generation and offspring were homozygote.(4) For the result of InDels site typing，in the certain extent,is consistent withSTR loci typing; in the exclude parentage relationship cases homozygote play moreroles for excluding; exclusive use30InDels site typing system to do parentage testingis not yet feasible.(5) InDels site typing can be done as supplement when STR mutation issuspect.