一例生长发育迟缓和智力障碍患儿的遗传学分析

Genetic study of a child with developmental delay and mental retardation

目的:明确1例生长发育迟缓、智力障碍患儿的遗传学病因。方法:应用常规G、C和N显带分析患儿外周血染色体,然后用单核苷酸微阵列芯片(single nucleotide polymorphisms array,SNP array)技术进行识别和定位,并应用荧光定量PCR技术验证。结果:患儿染色体核型为46,XX,r(22)(p12q13);SNP array拷贝数变异分析结果提示患儿染色体22q13.33区存在约1.4 Mb片段的拷贝数缺失:arr 22q13.33(49802963~51197766)×1,缺失片段中包含已知致病性明确、影响神经系统发育的SHANK3等基因。荧光定量PCR结果提示患儿SHANK3基因第7、19和22外显子的拷贝数约为正常对照的1/2,提示患儿携带该片段的杂合性缺失。结论:22号染色体q13.33区域的微缺失与患儿生长发育迟缓、智障等临床特征相关,遗传学分析为临床诊断提供了依据。

Objective To explore the genetic basis for a child with developmental delay and mental retardation.Methods Chromosomal karyotype of the child was analyzed by G-,C-and N-banding techniques.Her genome DNA was analyzed with single nucleotide polymorphisms array(SNP array).The result was validated by fluorescence quantitative polymerase chain reaction(PCR).Results The karyotype of the child was ascertained as 46,XX,r(22)(p12q13).SNP array has revealed a deletion of approximately 1.4 Mb at 22q13.33(49802963-51197766).The deletion has encompassed the SHANK3,a crucial gene for the development of nervous system.Fluorescence quantitative PCR has confirmed the deletion of exons 7,19 and 22 of the SHANK3 gene.Conclusion The phenotype of the patient may be attributed to the microdeletion at 22q13.33.Cytogenetic methods combined with SNP array and fluorescence quantitative PCR can identify aberrant chromosomes and provide accurate information for the clinical diagnosis and genetic counseling.