一例婴儿型Sandhoff病患儿的HEXB基因突变分析

摘要

目的 鉴定1例婴儿型Sandhoff病患儿HEXB基因的致病突变.方法 提取患儿外周血样DNA,应用PCR技术扩增其HEXB基因,并对PCR扩增产物进行直接测序,参考SNP数据库及ESP数据库进行比对.应用PubMed Protein BLAST系统分析HEXB基因编码的氨基已糖苷酶(Hex)的β亚基突变氨基酸的跨种属保守性;用PubMed BLAST CD-search系统分析Hex蛋白β亚基结构缺失所丧失的蛋白功能域;用PolyPhen-2、Mutation Taster及SIFT软件对新突变进行功能预测;通过全外显子基因组测序明确患儿有无其他可疑突变.结果 患儿携带HEXB基因c.1652G＞A(p.Cys551Tyr)和c.1389C＞G(p.Tyr463?)复合杂合突变.c.1389C＞G(p.Tyr463?)在SNP数据库中收录,经PubMed BLAST CD-search系统分析其编码的Hex蛋白β亚基结构存在2个关键的蛋白功能域的丧失,预测为可能有害突变;c.1652G＞A(p.Cys551Tyr)在SNP数据库及ESP数据库中均无收录,为未报道过的新突变,经PolyPhen-2、Mutation Taster及SIFT预测软件预测为可能有害突变.经全外显子基因组测序明确患儿除存在上述HEXB基因突变外不存在其他致病突变.结论 HEXB基因c.1652G＞A(p.Cys551Tyr)和c.1389C＞G(p.Tyr463?)复合杂合突变可能为该患儿的致病原因.基因突变检测可以为家系的遗传咨询和产前诊断提供依据.%Objective To detect potential mutations of HEXB gene in an infant with Sandhoff disease (SD).Methods Genomic DNA was extracted from peripheral blood sample of the infant. All coding exons (exons 1 to 14 )and splicing sites of the HEXB gene were subjected to PCR amplification and direct sequencing.PubMed Protein BLAST system was employed to analyze cross-species conservation of the mutant amino acid. PubMed BLAST CD-search was performed to identify functional domains destroyed by thecandidate mutations. Impact of the mutations was analyzed with software including PolyPhen-2, Mutation Taster and SIFT. Whole-exome sequencing was carried out to identify additional mutations.Results The infant was found to carry compound heterozygous mutations c.1652G > A (p.Cys551Tyr ) and c.1389C>G (p.Tyr463 ?)of the HEXB gene. The c.1389C > G (p.Tyr463 ?)mutation may lead to destruction of two functional domains in β subunit of the Hex protein. The c.1652G> A(p.Cys551Tyr) mutation, unreported previously, was predicted to be probably damaging by Bioinformatic analysis.Conclusion Compound heterozygous mutations c.1652G>A(p.Cys551Tyr)and c.1389C>G (p. Tyr463?)in the HEXB gene probably underlie the disease in this patient.