Delineation of a mosaicism fetal supernumerary marker chromosome with combined genetic techniques
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目的 联合应用染色体微阵列分析(CMA)、荧光原位杂交(FISH)和染色体核型分析对1例嵌合型微小额外标记染色体(sSMC)进行鉴定。 方法 以2022年深圳市龙华区妇幼保健院无创产前检测(NIPT)提示胎儿染色体4q12-4q13.1区存在8.75 Mb重复的1例孕妇作为研究对象，采集羊水样本与夫妇双方的外周血样进行染色体G显带核型分析，用CMA鉴定sSMC的来源和大小，之后用FISH对羊水中sSMC的嵌合比例进行进一步的确定。 结果 孕妇外周血G显带染色体核型为46，XX，其丈夫为46，XY，inv(9)(p12q12)，胎儿为47，XY，inv(9)(p12q12)pat，＋mar[75]/46，XY，inv(9)(p12q12)pat[25]。羊水CMA检测结果为arr[hg19]4p11q13.1(48978053_63145931)×3，并未显示嵌合。FISH检测经培养的分裂间期的羊水细胞中59%包含3个4号染色体的着丝粒信号，复抽羊水检查，有65%的分裂间期羊水细胞包含3个4号染色体着丝粒信号，证实羊水为三体嵌合体。 结论 结构异常合并嵌合性的sSMC需要在传统染色体核型分析的基础上结合其他检测技术进行精确的鉴定，为患者提供更准确的遗传咨询。 Objective To delineate the origin and content of a mosaicism small supernumerary marker chromosome (sSMC) in a fetus with combined chromosomal karyotyping, chromosomal microarray analysis (CMA) and fluorescence in situ hybridization (FISH). Methods The fetus of a 31-year-old pregnant woman who had presented at the Maternal and Child Health Care Hospital of Longhua District of Shenzhen City in 2022 was selected as the study subject. Non-invasive prenatal testing suggested that the fetus has harbored a 8.75 Mb duplication in 4q12q13.1. With informed consent, amniotic fluid and peripheral blood samples were taken from the couple for chromosomal karyotyping analysis. The origin and content of a sSMC was identified by CMA, and its proportion in amniotic fluid was determined with a FISH assay. Results The karyotypes of the pregnant woman, her husband and the fetus were respectively determined as 46, XX, 46, XY, inv(9)(p12q12), and 47, XY, inv(9)(p12q12)pat, + mar[75]/ 46, XY, inv(9)(p12q12)pat[25]. CMA test of the amniotic fluid sample was arr[hg19]4p11q13.1(48978053_63145931)×3, which revealed no mosaicism. However, FISH analysis showed that 59% of interphase cells from the cultured amniotic fluid sample had contained three signals for the centromere of chromosome 4, whilst 65% of interphase cells from the re-sampled amniotic fluid had three such signals, which confirmed the existence of trisomy 8 mosaicism. Conclusion Chromosomal structural abnormality combined with mosaicism can be delineated with combined chromosomal karyotyping and molecular techniques such as FISH and CMA, which has enabled more accurate counseling for the family.
Objective To delineate the origin and content of a mosaicism small supernumerary marker chromosome (sSMC) in a fetus with combined chromosomal karyotyping, chromosomal microarray analysis (CMA) and fluorescence in situ hybridization (FISH). Methods The fetus of a 31-year-old pregnant woman who had presented at the Maternal and Child Health Care Hospital of Longhua District of Shenzhen City in 2022 was selected as the study subject. Non-invasive prenatal testing suggested that the fetus has harbored a 8.75 Mb duplication in 4q12q13.1. With informed consent, amniotic fluid and peripheral blood samples were taken from the couple for chromosomal karyotyping analysis. The origin and content of a sSMC was identified by CMA, and its proportion in amniotic fluid was determined with a FISH assay. Results The karyotypes of the pregnant woman, her husband and the fetus were respectively determined as 46, XX, 46, XY, inv(9)(p12q12), and 47, XY, inv(9)(p12q12)pat, + mar[75]/ 46, XY, inv(9)(p12q12)pat[25]. CMA test of the amniotic fluid sample was arr[hg19]4p11q13.1(48978053_63145931)×3, which revealed no mosaicism. However, FISH analysis showed that 59% of interphase cells from the cultured amniotic fluid sample had contained three signals for the centromere of chromosome 4, whilst 65% of interphase cells from the re-sampled amniotic fluid had three such signals, which confirmed the existence of trisomy 8 mosaicism. Conclusion Chromosomal structural abnormality combined with mosaicism can be delineated with combined chromosomal karyotyping and molecular techniques such as FISH and CMA, which has enabled more accurate counseling for the family.
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