Analysis Of Common And Rare Thalassemias Genotypes In Sanming,Fujian

AimsThe main purposes of this study include analysising the distribution of different Thalassemias genotypes in Sanming,Fujian;creating databases monitoring the mutation rate of Thalassemias in local Sanming area;and having this genetics database to support clinical genetic counseling.The corresponding genetic database will afterward optimize the Thalassemias prenatal diagnosis in Sanming and benefit the reduction of misdiagnosis and birth defect related to the disease.MethodsWhole blood was collected from patients for testing of thalassemias or patients for the premarital screening and genetic counseling in Sanming First Hospital from April2016 to December 2020.PCR with flow-through hybridization approach was conducted as common thalassemias detection for samples under the situations of:⑴blood routine MCV<80 f L and/or MCH>27 pg;or⑵unusual hemoglobin electrophoresis values.DNA agarose gel electrophoresis or the first-generation sequencing approaches were performed as rare thalassemias detections for subjects that has unmatched genotypes with phenotypes.In addition,amniocentesis was conducted on high risk women under pregnancy for fetal thalassemias genotype detection.ResultsWhole blood samples from a total of 6975 subjects were screened for thalassemia with 2744（overall prevalence 39.34%）of them detected positive for thalassemias,which included 2653 common thalassemias（prevalence 38.04%）and 91 rare thalassemia（prevalence 1.30%）.（1）Common genotype test results:a)A total of 1833 subjects were identified asα-thalassemia（n=1321,prevalence26.28%）,with the prevalence of which ranked from highest to lowest were--^SEA/αα（prevalence 18.94%）,-α^3.7/αα（n=274,prevalence 3.90%）,and others（n=238,prevalence 3.41%）.b)A total of 711 subjects were identified asβ-thalassemia（prevalence 11.05%）,with the prevalence of which ranked from highest to lowest wereβ^{IVS-II-654（C→T）}/β^N（n=354,prevalence 5.08%）,β^{CD41-42（-TCTT）}/β^N（n=246,prevalence 3.53%）,and others（n=171,prevalence 2.45%）.c)A total of 49 subjects were identified as concurrentα-andβ-thalassemias（prevalence 0.70%）,with the prevalence of which ranked from highest to lowest were-α^3.7/αα/β^{IVS-II-654（C→T）}/β^N（prevalence 0.20%）,--^SEA/αα/β^{IVS-II-654（C→T）}/β^Nand-α^3.7/αα/β^{CD41-42（-TCTT）}/β^N（prevalence 0.09%）,and others（prevalence 0.42%）.（2）Results of rare genotype testing:a)A total of 60 subjects were identified asα-thalassemia,including deletion and mutation.Among these rareα-thalassemia ones,41 cases wereαdeletion sequence,including--^THAI/αα（n=36）,HKαα/--^SEA（n=2）,ααα^anti3.7/αα（n=1）,ααα^anti4.2/αα（n=1）and--^THAI/αα^4.2（n=1）.There were 19α-mutations,includingαα^{CD30（GAG>CAG）}/αα（n=5）,ααIVS-II-34（G>A）/αα（n=4）,ααHBA2:c.*29（C>T）/αα（n=1）,ααHBA2:c.91（G>C）/αα（n=1）,ααCD74（GAC>CAC）/αα（n=1）,ααCD 89（CAC>CGC）/αα（n=1）,ααCD117/118（+ATC）/αα（n=1）,-α4.2/ααCD74（GAC>CAC）（n=1）,--SEA/-α4.2αCD74（GAC>CAC）（n=1）,ααIVS-II-55（T>G）/αα（n=1）,ααCD59（GGC>CGC）/αα（n=1）,ααCD59（GGC>CGC）/ααCAP+14（C>G）（n=1）andααIVS-II-34（G>A）/αα（n=1）.b)A total of 29 subjects were identified asβ-thalassemia,including 10 mutation types:βCD113（GTG>GAG）/βN（n=12）,βCD56（GGC>GAC）/βN（n=8）,βCAP+22（G>A）/βN（n=2）,βChinese（Aγδβ）0/βN（n=1）,βCD22（GAA>GGA）/βN（n=1）,βIVS-I-2/βN（n=1）,βIVS-II-143（G>A）/βN（n=1）,βIVS-^{II-781（C>G）}/β^N（n=1）,β^-90（C>T）/β^N（n=1）,β¹³¹（CAG>AAG）/β^N（n=1）.There are two novel mutations among these types that appears the first time in Sanming area:β¹³¹/β^NandβIVS II-143/βN.c)There were 2 cases of concurrentα-andβ-thalassemias,includingααIVS-II-55（T>G）/αα/βCD54-58（-13bp）/βN（n=1）,as well asαααanti3.7/αα/βCD27-28（+C）/βN（n=1）.（3）Prenatal diagnosis results:In terms of fetal thalassemias genotype detection,98 out of 127 amniocentesis subjects were thalassemias positive.a)A total of 87 subjects were detected asα-thalassemias（prevalence 68.5%）with 17belong to staticα-thalassemias;13 belong to minorα-thalassemias;14 belong to intermediateα-thalassemias,;and 15 belong to majorα-thalassemias.b)A total of 10 subjects were detected asβ-thalassemias（prevalence 8.67%）with 8belong to minorβ-thalassemias;3 belong to intermedia or majorβ-thalassemias.c)A total of 1 subjects was detected as concurrentα-andβ-thalassemias.Conclusions:This study filled the gaps in related research fields in Sanming by establishing a gene bank for common and rare thalassaemias in Sanming,and provided accurate data support for clinical genetic counseling on thalassaemias.The detection rate of rare thalassaemia in Sanming area reached 1.3%,among whichβ¹³¹/β^Nandβ^IVS-II-143/β^Nare two new mutations reported for the first time in Sanming area.Therefore,great attention should be paid to rare thalassaemia mutations or deletions in Sanming area.Detection of sites.