两个肢带型肌营养不良2D型家系SGCA基因遗传分析和产前诊断

SGCA gene mutation analysis and prenatal diagnosis of two pedigrees with limb-girdle muscular dystrophy type 2D

目的对中国汉族肢带型肌营养不良2D(limb-girdle muscular dystrophy type 2D,LGMD2D)型的2个家系进行SGCA基因分析,明确病因并在此基础上为该家系中的胎儿进行产前诊断,提供遗传咨询与指导。方法回顾性收集2017年6月至2018年1月在郑州大学第一附属医院就诊的2个LGMD2D型家系,提取先证者和其父母的外周血,通过探针杂交技术对先证者LGMD相关21个基因编码区及其侧翼序列进行高通量测序,进一步采用Sanger测序和/或荧光定量聚合酶链反应对先证者父母目标基因区域进行检测,同时验证变异来源;明确先证者病因后,进一步对家系中胎儿进行产前诊断。结果家系1:先证者存在SGCA基因c.218C>G(p.P73R)和c.101G>A(p.R34H)复合杂合变异;产前诊断结果显示,胎儿与先证者一样同时遗传了父母双方的致病变异,胎儿父母选择终止妊娠。家系2:先证者携带SGCA基因c.218C>T(p.P73L)和该基因第7和第8外显子杂合缺失复合杂合变异,但胎儿不携带上述两变异,家属选择继续妊娠。胎儿足月分娩,随访至2岁,肌酶谱、体格、运动和智力发育均未见异常。结论SGCA基因复合杂合突变是2个LGMD2D型家系的致病原因,其中c.218C>G(p.P73R)、c.218C>T(p.P73L)为尚未报道的新突变。基于高通量测序可快速、准确地对该病进行基因诊断和产前诊断。

Objective To analyze the variations of SGCA gene in two Chinese pedigrees of Han nationality with limb-girdle muscular dystrophy type 2D(LGMD2D)and provide prenatal diagnosis and genetic counseling for subsequent pregnancies within the pedigrees.Methods This study involved two unrelated patients who were the probands of their pedigrees diagnosed with LGMD2D in the First Affiliated Hospital of Zhengzhou University from June 2017 to January 2018.Genomic DNA was extracted from peripheral blood samples of the probands and their parents.Coding sequences and flanking sequences of 21 LGMD-related genes from the probands were captured and subjected to high-throughput sequencing.Suspected mutations in their parents were detected and validated by Sanger sequencing and/or fluorescence quantitative polymerase chain reaction(PCR).Prenatal genetic diagnosis for high-risk fetuses in the two pedigrees was performed after the causative factors being identified.Results(1)The proband of pedigree 1 carried compound heterozygous point mutations in SGCA gene with c.218C>G(p.P73R)and c.101G>A(p.R34H)inherited from his father and mother,respectively.Prenatal diagnosis indicated that the second fetus of the family carried the same mutations as the proband,and the family chose to terminate the gestation.(2)The proband of pedigree 2 inherited the compound heterozygous mutations of c.218C>T(p.P73L)and heterozygous deletion of exons 7 and 8 in SGCA gene from his parents.Their second fetus did not carry any of the above mutations and was delivered at full term.Serum creatinase level and physical,motor and mental development of the child were all within the normal range during a two-year follow-up after birth.Conclusions The heterozygous mutations in SGCA gene are the cause of LGMD2D in the two pedigrees,and c.218C>G(p.P73R)and c.218C>T(p.P73L)are novel mutations.Genetic and prenatal diagnosis based on high-throughput targeted next-generation sequencing can rapidly and accurately detect the mutations responsible for LGMD2D.