遗传性球形红细胞增多症患儿16例的SPTB基因变异特征分析

Analysis of the characteristics of SPTB gene variants among 16 children with Hereditary spherocytosis

目的分析16例SPTB基因变异所致遗传性球形红细胞增多症(HS)患儿的临床特征和变异谱,探讨变异类型与HS临床表型的相关性。方法选择2018年11月至2022年7月就诊于首都儿科研究所附属儿童医院血液科门诊的HS患儿为研究对象。收集患儿的临床资料,采用全外显子组测序对患儿进行检测,对候选变异进行Sanger测序家系验证,同时进行生物信息学分析和蛋白三维结构预测。采用χ^(2)检验比较具有不同蛋白质功能结构域的SPTB基因变异位点的患儿的临床表型差异。结果16例HS患儿的男、女比例为6:10,中位发病年龄为7岁10个月,主要临床表现为贫血、黄疸、网状红细胞增多,其中轻、中、重度贫血占比分别为56.25%(9/16)、31.25%(5/16)、12.50%(2/16)。基因检测结果显示,16例HS患儿均携带SPTB基因变异,其中10种变异既往未见报道,7例患儿的变异为新发。生物信息学分析显示,16例HS患儿中SPTB基因功能丧失型变异(LOF)占93.75%(15/16),错义变异占6.25%(1/16);变异位点分别位于收缩蛋白部分重复结构域(68.75%,11/16)、肌动蛋白结合域CH1(25.00%,4/16)和二聚化结构域(6.25%,1/16)。χ^(2)检验显示,变异位点位于不同功能结构域的患儿的贫血程度差异无统计学意义(χ^(2)=3.345,P>0.05)。蛋白三维结构预测结果显示,c.253G>A(p.G85R)错义变异可能影响蛋白质的正确折叠和二聚化的氢键网络,导致蛋白结构的异常;其余15种LOF变异可产生相应的截短蛋白,影响收缩蛋白的功能。根据美国医学遗传学与基因组学学会相关指南,上述变异均被评判为致病或可能致病。结论16例携带SPTB基因变异的HS患儿中轻中度贫血占比较高,变异类型以LOF为主,不同功能结构域的变异并不影响HS患儿的临床表现。本研究丰富了SPTB基因的致病变异谱和临床表型谱。

Objective To analyze the clinical characteristics and spectrum of SPTB gene variants among 16 Chinese children with Hereditary spherocytosis(HS)and explore their genotype-phenotype correlation.Methods Sixteen children who were diagnosed with HS at the Affiliated Hospital of Capital Institute of Pediatrics from November 2018 to July 2022 were selected as the research subjects.Genetic testing was carried out by whole exome sequencing.Candidate variants were verified by Sanger sequencing and subjected to bioinformatic analysis and prediction of 3D structure of the protein.Correlation between the SPTB genotypes and clinical phenotypes was analyzed using Chi-squared test.Results The male-to-female ratio of the HS patients was 6:10,with the median age being 7-year-and-10-month.Clinical features of the patients have included anemia,reticulocytosis and gradual onset of splenomegaly.Mild,moderate and severe anemia have respectively occurred in 56.25%(9/16),31.25%(5/16)and 12.50%(2/16)of the patients.SPTB gene variants were detected in all patients,among which 10 were unreported previously and 7 were de novo in origin.Loss of function(LOF)variants accounted for 93.75%(15/16).Only one missense variant was detected.Eleven,4 and 1 of the variants had occurred in the repeat domain,CH1 domain,and dimerization domain,respectively.There was no significant correlation between the type or domain of the SPTB gene variants with the clinical features such as severity of anemia(χ^(2)=3.345,P>0.05).All of the variants were predicted to be pathogenic or likely pathogenic based on the guidelines from the American College of Medical Genetics and Genomics.Conclusion Mild to moderate anemia are predominant clinical features of the HS children harboring a SPTB gene variant,for which LOF variants are the main mutational type.The clinical feature of HS is unaffected by the type of the variants.Above finding has enriched the spectrum of SPTB gene variants and its clinical phenotypes.