Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Pan-Chiao, Taiwan.
Taiwan J Obstet Gynecol. 2010 Sep;49(3):341-50. doi: 10.1016/S1028-4559(10)60071-X.
To present prenatal diagnosis and molecular genetic analyses of mosaic trisomy 9.
MATERIALS, METHODS AND RESULTS: A 35-year-old woman, gravida 3, para 1, underwent amniocentesis at 17 weeks of gestation because of her advanced maternal age. Amniocentesis revealed a karyotype of 47,XX,+9[3]/46,XX[6]. Repeat amniocentesis at 19 weeks of gestation revealed a karyotype of 47,XX,+9[6]/46,XX[19]. At 22 weeks of gestation, she was referred to a tertiary medical center for genetic counseling, and amniocentesis revealed a karyotype of 47,XX,+9[2]/46,XX[22]. Array comparative genomic hybridization analysis of uncultured amniocytes revealed no genomic imbalance in chromosome 9. However, interphase fluorescence in situ hybridization analysis of uncultured amniocytes showed that nine (18%) of 50 cells were trisomic for chromosome 9. Polymorphic DNA marker analyses also revealed a diallelic pattern with unequal biparental inheritance of chromosome 9 and a dosage ratio of 1:18 (paternal allele:maternal allele) in the uncultured amniocytes and a dosage ratio of 1:36 in the cultured amniocytes, indicating that the euploid cell line had maternal uniparental isodisomy for chromosome 9. Level II ultrasound demonstrated bilateral ventriculomegaly. The pregnancy was subsequently terminated, and a malformed fetus was delivered. Postnatal cytogenetic and polymorphic DNA marker analyses of the fetal and extraembryonic tissues confirmed the prenatal diagnosis.
Mosaic trisomy 9 carries a high risk of fetal abnormalities warranting detailed sonographic investigation of congenital malformations. Mosaic trisomy 9 can be associated with maternal uniparental disomy for chromosome 9 in euploid cell lines. Array comparative genomic hybridization is limited for the detection of low-level mosaicism.
介绍嵌合体性 9 号三体的产前诊断和分子遗传学分析。
材料、方法和结果：一名 35 岁的高龄产妇，妊娠 3 次，产 1 次，在妊娠 17 周时因高龄接受羊膜穿刺术。羊膜穿刺术显示核型为 47,XX,+9[3]/46,XX[6]。妊娠 19 周时重复羊膜穿刺术，显示核型为 47,XX,+9[6]/46,XX[19]。妊娠 22 周时，她被转介到一家三级医疗中心进行遗传咨询，羊膜穿刺术显示核型为 47,XX,+9[2]/46,XX[22]。未培养的羊水细胞的比较基因组杂交分析未显示 9 号染色体基因组失衡。然而，未培养的羊水细胞的间期荧光原位杂交分析显示，9 号染色体有 9 个（18%）细胞呈三体性。多态性 DNA 标记分析还显示，未培养的羊水细胞存在染色体 9 的二等位基因模式，具有非均等双亲遗传和 1:18 的剂量比（父本等位基因：母本等位基因），而在培养的羊水细胞中存在 1:36 的剂量比，表明正常核型细胞系存在母源单亲二体性 9 号染色体。二级超声显示双侧脑室扩大。随后终止妊娠，分娩出畸形胎儿。产后胎儿和胚胎外组织的细胞遗传学和多态性 DNA 标记分析证实了产前诊断。
嵌合体性 9 号三体具有胎儿异常的高风险，需要对先天性畸形进行详细的超声检查。嵌合体性 9 号三体可能与正常核型细胞系中的母源单亲二体性 9 号染色体有关。比较基因组杂交的阵列检测对于低水平嵌合体性有限。
