一个枫糖尿病新发突变家系的遗传学分析及产前诊断应用

Genetic analysis and prenatal diagnosis for a nevo mutation pedigree affected with maple syrup urine disease

目的对1例枫糖尿症(maple syrup urine disease,MSUD)患者家系的基因突变,明确其遗传学病因,并应用于产前诊断。方法选取2017年在深圳市妇幼保健院新生儿科诊断的一例枫糖尿症患儿,女孩,发病年龄为出生后6天,采用二代高通量测序方法对患儿及父母进行BCKDHA基因、BCKDHB基因、DBT基因、DLD基因4个基因外显子编码区进行序列的捕获及测序,确定可疑的突变位点。用Sanger测序进行验证。应用生物信息学软件预测突变位点的氨基酸进化保守性和蛋白质结构及功能变化,并在患儿母亲再次妊娠时抽取胎儿绒毛组织,提取DNA,对相应的基因突变进行检测,用于产前诊断。结果高通量测序发现患儿BCKDHB基因双重杂合突变,为第7外显子c.818C>T,第9外显子c.988G>A两个基因错义突变,其中c.818C>T遗传自于患儿母亲,c.988G>A遗传自于患儿父亲。c.818C>T为未报道过的新突变。两个突变位点均位于高度保守区域,突变导致相应氨基酸和蛋白质的结构及功能变化,从而影响支链氨基酸脱氢酶复合体的活性。患儿母亲再次妊娠未检测到BCKDHB基因相关突变。结论通过二代测序技术对枫糖尿症患儿家系相关基因序列的捕获及测序,了解MSUD的患儿的突变情况,且发现一个未报道过的新突变。并成功用于产前诊断。

Objective:A genetic mutation in a family of patients with maple syrup urine disease(MSUD),identifying the genetic cause and applying it to prenatal diagnosis. Methods:A case of children with maple syrup diagnosed in the neonatology department of Shenzhen Maternal and Child Health Hospital in 2017,girl,age of onset is 6 days after birth,The second generation high-throughput sequencing method was used to capture and sequence the four gene exon coding regions of BCKDHA gene,BCKDHB gene,DBT gene and DLD gene in children and parents to identify suspicious mutation sites.Validation with Sanger sequencing.Application of Bioinformatics Software to Predict Amino Acid Evolution Conservation and Protein Structure and Function Changes of Mutation Sites. And when the mother is pregnant again,the fetal villus tissue is taken,the DNA is extracted,and the corresponding gene mutation is detected for prenatal diagnosis. Results:High-throughput sequencing revealed a double heterozygous mutation in the BCKDHB gene in children,which was the 7 th exon c.818 C>T,the 9 th exon c.988 G>A two gene missense mutations.Where c.818 C>T is inherited from the mother,c.988 G>A is inherited from the father.c.818 C>T is a new mutation that has not been reported.Both mutation sites are located in highly conserved regions,and the mutations lead to changes in the structure and function of the corresponding amino acids and proteins,thereby affecting the activity of the branched-chain amino acid dehydrogenase complex.BCKDHB gene-related mutations were not detected in the mother’s second pregnancy. Conclusion:The second generation of sequencing technology was used to capture and sequence the gene sequences of children with MUSD,to understand the mutations of children with MSUD,and to find a new mutation that was not reported.And successfully used in prenatal diagnosis.