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目的探讨传统细胞遗传学技术联合SNP-array(single nucleotide polymorphisms array,SNP-array)在识别胎儿微小额外标记染色体(supernumerary marker chromosome,sSMC)致病性中的临床应用价值。方法通过常规G显带技术分析胎儿染色体核型,针对发现的sSMC,应用C显带技术分析sSMC,如果sSMC非异染色质,进一步进行SNP-array辨别其来源并分析相应的表型。结果通过对8575例产前诊断标本G显带核型分析发现4例新发标记染色体,其中C显带示2例为异染色质结构,2例为非异染色质结构。这2例非异染色质结构病例进一步行SNP-array检测,结果示一例未见致病性改变,另一例为4号染色体部分重复。结论 SNP-array能够在基因组水平上识别胎儿sSMC的成分,结合传统的细胞遗传学技术应用于产前诊断中,为确定sSMC的致病性提供了可靠的产前诊断技术平台。
Objective To investigate the clinical value of SNP-array (SNP-array) in identifying the pathogenicity of fetal extra-small marker chromosome (sSMC). Methods Fetal chromosome karyotypes were analyzed by conventional G-banding technique. The sSMCs were analyzed by C-banding technique for sSMCs detected. If the sSMCs were not heterochromatic, SNPs were further identified and their phenotypes analyzed. Results Four cases of newly-labeled chromosomes were found in G-banding karyotype analysis of 8575 cases of prenatal diagnosis specimens. C-banding revealed two cases of heterochromatin structure and two cases of non-heterochromatin structure. The two cases of non-heterochromatin structure further SNP-array detection, the results showed no case of pathogenic changes in one case, the other is part 4 chromosome duplication. Conclusion SNP-array can identify the components of fetal sSMC at the genomic level, and can be used in prenatal diagnosis combining with traditional cytogenetics. It provides a reliable prenatal diagnosis platform for determining the pathogenicity of sSMC.