Li Wenwen, Fang Rong, Shen Xueping, Yao Juan, Xue Jianying, Shen Guosong
Prenatal Diagnosis Center, Huzhou Women and Children's Health Care Hospital, Huzhou, Zhejiang 313000, China.
Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 2020 Dec 10;37(12):1344-1348. doi: 10.3760/cma.j.cn511374-20190919-00481.
To explore the origin and mechanism of small supernumerary marker chromosomes (sSMC) in three fetuses.
The three fetuses were predicted to have carried chromosomal abnormalities by non-invasive prenatal testing (NIPT). G-banding chromosomal karyotyping analysis were carried out on amniotic fluid samples of the fetuses and peripheral blood samples from their parents. Single nucleotide polymorphism array (SNP-array) was used to determine the origin, size and genetic effect of sSMCs.
In fetus 1, SNP array has detected two microduplications respectively at 4p16.3p15.2 (24.7 Mb) and 18p11.32q11.2 (20.5 Mb) which, as verified by fluorescence in situ hybridization (FISH), have derived from a balanced 46,XY,t(4;18)(p15.2q11.2) translocation carried by its father. Fetus 2 has carried a de novo microduplication of 15q11.2-q13.3 (9.7 Mb). The sequence of SMC in fetus 3 has derived from 21q11.2-q21.1 (8.3 Mb), which was inherited from its mother.
Both NIPT and SNP-array are highly accurate for the detection of sSMC. SNP-array can delineate the origin and size of abnormal chromosomes, which in turn can help with clarification of sSMC-related genotype-phenotype correlation and facilitate prenatal diagnosis and genetic counseling for the family.
探讨3例胎儿小额外标记染色体（sSMC）的起源及机制。
3例胎儿经无创产前检测（NIPT）预测携带染色体异常。对胎儿羊水样本及其父母外周血样本进行G显带染色体核型分析。采用单核苷酸多态性阵列（SNP阵列）确定sSMC的起源、大小及遗传效应。
胎儿1中，SNP阵列分别在4p16.3p15.2（24.7 Mb）和18p11.32q11.2（20.5 Mb）检测到两个微重复，经荧光原位杂交（FISH）验证，其来源于父亲携带的平衡易位46,XY,t(4;18)(p15.2q11.2)。胎儿2携带15q11.2 - q13.3（9.7 Mb）的新发微重复。胎儿3的SMC序列来源于21q11.2 - q21.1（8.3 Mb），是从母亲遗传而来。
NIPT和SNP阵列对sSMC的检测均具有较高准确性。SNP阵列能够明确异常染色体的起源和大小，进而有助于阐明sSMC相关的基因型 - 表型相关性，并为家庭提供产前诊断和遗传咨询。
