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目的应用高通量基因测序技术对产前诊断过程中发现的1例胎儿额外小标记染色体的来源和大小进行鉴定,进一步分析其遗传效应。方法通过羊水培养、染色体G显带技术进行羊水细胞核型分析,诊断出1例胎儿额外小标记染色体,染色体核型为47,XN,+mar。应用高通量基因测序技术,对该羊水细胞进行测序分析,从而确定小标记染色体的大小、具体区域范围、遗传效应。结果羊水细胞染色体核型分析结果为47,XN,+mar。高通量基因测序结果显示14q11.2(19460001-20440000)×3,重复片断大小为0.98Mb;15q11.1q11.2(20180001-22500000)×3,重复片断大小为2.32Mb;16p11.2(32500001-33900000)×3,重复片断大小为1.40Mb。查询公共数据库显示:14号染色体重复区域,为多态性;15号染色体重复区域,为多态性;16号染色体重复区域,为多态性。结论产前诊断过程中,由于普通细胞遗传学方法的局限性,额外小标记染色体的遗传咨询充满挑战,而高通量测序技术可以在基因组水平明确额外小标记染色体的大小、具体区域范围,为判断额外小标记染色体的遗传效应和遗传咨询提供帮助。
Objective To identify the origin and size of an extra fetal small marker chromosome detected in prenatal diagnosis by high-throughput sequencing and further analyze its genetic effect. Methods An amniotic fluid cell karyotype analysis was performed by amniotic fluid culture and G - banding technique. One additional fetus was identified as small marker chromosome with karyotype 47, XN, + mar. High-throughput sequencing technology was applied to sequencing the amniotic fluid cells to determine the size, specific region and genetic effect of small marker chromosomes. Results The amniotic fluid cell karyotype analysis results were 47, XN, + mar. High-throughput gene sequencing results showed 14q11.2 (19460001-20440000) × 3, the size of the repeat fragment was 0.98Mb; 15q11.1q11.2 (20180001-22500000) × 3, the size of the repeat fragment was 2.32Mb; 16p11.2 (32500001 -33900000) × 3, the repeat fragment size is 1.40Mb. Public database query revealed that chromosome 14 was polymorphic, chromosome 15 was polymorphic, and chromosome 16 was polymorphic. Conclusion In the process of prenatal diagnosis, the genetic counseling of additional small marker chromosomes is challenging due to the limitations of common cytogenetic methods. However, the high-throughput sequencing technique can clearly define the size of additional small marker chromosomes at the genomic level. The specific regional range is To determine the genetic effects of additional small marker chromosomes and genetic counseling to help.