CDAN1基因突变导致的胎儿期非免疫性水肿的家系遗传学分析

目的 对一例因不明原因胎儿期水肿的流产组织进行临床和遗传学分析，为该家系产前诊断以及遗传咨询提供可靠的理论依据。方法 采集孕妇外周血进行血常规、Rh血型和TORCH检测。采集羊水细胞用于细胞培养和G显带核型分析。提取胎儿引产组织基因组DNA行全基因组拷贝数变异测序；采用Agilent's SureSelect XT Human All Exon V6进行文库制备和外显子捕获,并使用Illumina NovaSeq 6000 对胎儿及其家系成员 DNA 行全外显子组测序（trios-WES），并利用SIFT、I-mutant2、PolyPhen-2 及PROVEAN生物信息学软件对变异位点进行蛋白功能预测。利用Alpha Fold 2和PyMOL软件对CDAN1的结构进行建模和可视化分析；用Sanger测序对先证者及家系成员进行突变检测和验证。结果 胎儿17周超声提示胎儿全身皮下广泛水肿，右侧胸腔大量积液，肝脾增大，胎盘增厚，心包缺损。染色体核型分析检测和染色体拷贝数变异测序结果均正常；全外显子组测序显示CDAN1基因：c.2140C>T（p.Arg714Trp）和c.1264_1265delCT（p.Leu422Glyfs*16）复合杂合突变，分别来自先证者父亲和母亲，生物信息学预测为可能致病性突变，对应的疾病为先天性红细胞生成障碍性贫血1型。结论 全外显子组测序结果显示，该胎儿为先天性红细胞生成障碍性贫血（CDAN1基因突变）导致的胎儿期非免疫性水肿，其中CDAN1基因c.1264_1265delCT为首次报道的突变。

Whole exome sequencing analysis of compound heterozygous variants of CDAN1 gene in a Chinese family with non-immune hydrops fetalis

Objective To study the clinical characteristics and genetic variants in a family with non-immune hydrops fetalis. Methods Peripheral blood samples were collected from a pregnant woman with suspected non-immune hydrops fetalis of the fetus for routine blood analysis, Rh typing and TORCH test. Amniotic fluid sample was collected for G-banded chromosomal karyotyping. The gnomic DNA of the proband was extracted for analysis of chromosomal abnormalities using copy number variation sequencing. Whole-exome sequencing (Trios-WES) was performed on Illumina NovaSeq 6000 platform and exonic DNA was enriched using Agilent Sure Select XT Human All Exon V6. Sorting intolerant from tolerant (SIFT), I-mutant2, PolyPhen-2 and PROVEAN were used to predict the potential effects of amino acid substitution on protein function and splicing variation. The spatial structure of codanin-1 was modeled and visualized with Alpha Fold 2 and PyMOL 2.3 software, and the variants with potential clinical significance were confirmed by Sanger sequencing. Results Fetal ultrasound at 17 weeks of gestation showed extensive subcutaneous edema, ascites, pleural effusion, enlarged liver and spleen, thickened placenta and pericardium defect. NGS reveals that proband has carried c.2140C>T, p.R714W, and c.1264_1265delCT, p.L422* compound heterozygous variants of CDAN1 gene, which were found to be pathogenic and inherited from proband’s father and mother respectively. Conclusion We identified a novel heterozygous CDAN1 gene mutation causing fetal-onset congenital dyserythropoietic anemia type 1, which triggers non-immune hydrops fetalis.