Fan Jiaming, Zeng Yan, Luo Tingting, Che Ming
Shaoxing Women and Children's Health Care Hospital, Shaoxing, Zhejiang 312000, China.
Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 2021 Mar 10;38(3):264-267. doi: 10.3760/cma.j.cn511374-20200227-00106.
To delineate the origin and structure of 3 cases of small supernumerary marker chromosomes (sSMCs) through cytogenetic and molecular genetic analysis.
Conventional G, C and N banding were carried out to analyze the chromosomal karyotypes. Chromosomal microarray analysis (CMA) and fluorescence in situ hybridization (FISH) were used to delineate the origin and structure of the sSMCs.
In case 1, chromosomal karyotype of peripheral blood sample was 47,XY,+mar. This de novo sSMC was a dual-satellited dicentric inverted duplicated marker chromosome, for which CMA yielded a normal result. It was predicted to not increase the risk of offspring. In case 2, the fetal chromosomal karyotype was 47,XY,+mar[17]/46,XY[33]. Chromosomal banding suggested that this de novo segment contained euchromatin, and the result of CMA was arr[hg19] 5p12q11.1(45 694 574-49 475 697) × 3. FISH showed the sSMC to be a fragment derived from 5p12 containing the HCN1 gene. Case 3 was found to have a fetal karyotype of 45,XY,-13[25]/46,XY,r(13)[18]/46,XY,-13,+mar[7]. Both parents had refused further examination.
Conventional chromosomal banding combined with molecular methods can delineate the origin and structure of the sSMCs, which can help with prediction of their pathogenicity and facilitate genetic counseling.
通过细胞遗传学和分子遗传学分析，明确3例小额外标记染色体（sSMC）的起源和结构。
采用常规G、C和N显带技术分析染色体核型。运用染色体微阵列分析（CMA）和荧光原位杂交（FISH）技术明确sSMC的起源和结构。
病例1，外周血样本染色体核型为47,XY,+mar。这条新发的sSMC是一条双随体双着丝粒倒位重复标记染色体，CMA结果正常。预计其不会增加子代风险。病例2，胎儿染色体核型为47,XY,+mar[17]/46,XY[33]。染色体显带提示这条新发片段包含常染色质，CMA结果为arr[hg19] 5p12q11.1(45 694 574-49 475 697)×3。FISH显示sSMC是一条源自5p12包含HCN1基因的片段。病例3，胎儿核型为45,XY,-13[25]/46,XY,r(13)[18]/46,XY,-13,+mar[7]。父母均拒绝进一步检查。
常规染色体显带与分子方法相结合可明确sSMC的起源和结构，有助于预测其致病性并促进遗传咨询。
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