全外显子组测序鉴定7q36.3微重复的胎儿多指并指畸形

doi:10.12280/gjszjk.20240053

摘要/Abstract

摘要：

目的：对一个家族遗传性多指并指畸形进行临床及分子遗传学分析。方法：对1个孕期提示胎儿多指并指畸形的家系行产前诊断。孕24⁺⁵周于泉州市妇幼保健院·儿童医院产前诊断行羊水穿刺，利用染色体核型分析对胎儿行染色体异常诊断。同时，利用全外显子组测序（whole exome sequencing，WES）分析胎儿微小变异。此外，通过实时荧光定量聚合酶链反应（quantitative real time polymerase chain reaction，qPCR）进行微缺失/微重复验证。结果：胎儿染色体核型结果未见异常。胎儿WES检测结果显示在7q36.3区域存在一个803.7 kb片段重复（seq[GRCh37]7q36.3(155865332_156669022)×3），包含RNF32基因以及LMBR1基因的2~17号外显子。依据美国医学遗传学与基因组学学会（the American College of Medical Genetics and Genomics，ACMG）指南，该重复判读为致病性。父母qPCR验证提示，该重复遗传自具有同样表型的父亲。结论：明确了7q36.3微重复为胎儿多指并指畸形遗传病因，该重复可能导致了三指节拇指-多并指/趾畸形综合征，其中LMBR1为其主要起效基因。

关键词: 多指（趾）畸形, 并指（趾）, 病因诊断, 全外显子组测序, 核型分析, 产前诊断, 拷贝数变异

Abstract:

Objective: To conduct clinical and molecular genetic analysis in a Chinese family with familial polysyndactyly. Methods: A pregnant woman with fetal polysyndactyly was enrolled in this study, amniocentesis was performed at Quanzhou Women′s and Children′s Hospital for prenatal diagnosis at the gestational age of 24⁺⁵ weeks. Chromosomal karyotype analysis was performed to reveal fetal chromosomal abnormalities. Subsequently, whole exome sequencing (WES) was carried out to analyze sequence variations. Quantitative real time polymerase chain reaction(qPCR) was use to confirm the detected microdeletion/microduplication. Results: The fetal chromosome karyotype results elicited a normal karyotype result. However, WES demonstrated an 803.7 kb fragment duplication (seq[GRCh37]7q36.3(155865332_156669022)×3) in the 7q36.3 region in the fetus, which covering RNF32 and LMBR1 (exon 2 to exon 17). According to the American College of Medical Genetics and Genomics(ACMG) guidelines, the 7q36.3 duplication was interpreted as pathogenic copy number variants. The subsequent qPCR verification indicated that the duplication was inherited from the father who had similar clinical phenotype. Conclusions: Our findings further confirm that 7q36.3 microduplication is the genetic cause for fetal polysyndactyly, which may lead to triphalangeal thumb-polysyndactyly syndrome, LMBR1 may be the main effector gene.

Key words: Polydactyly, Syndactyly, Etiology diagnosis, Whole exome sequencing, Karyotype analysis, Prenatal diagnosis, Copy number variants

庄建龙, 许伟雄, 江矞颖. 全外显子组测序鉴定7q36.3微重复的胎儿多指并指畸形[J]. 国际生殖健康/计划生育杂志, 2024, 43(4): 284-288.

ZHUANG Jian-long, XU Wei-xiong, JIANG Yu-ying. Whole Exome Sequencing Identified A 7q36.3 Microduplication in A Fetus with Polysyndactyly[J]. Journal of International Reproductive Health/Family Planning, 2024, 43(4): 284-288.

图/表 7

图1 胎儿产前超声图注：A 左侧拇指外侧见一骨性突起，长约1.1 cm，并与左侧拇指呈“并指”状态。B 右侧拇指外侧见一骨性突起，长约1.81 cm，与右侧拇指完全分开。

图2 家系图注：箭头所示为先证者。□ 正常男性，○ 正常女性，■ 男性患者，● 女性患者。

表1 引物序列

引物编号	正向引物（5′→3′）	反向引物（5′→3′）
LMBR1-1	TGGTGACTCTCCTTTCTTCCA	CATGAATCAGGGAGCCATTT
LMBR1-2	TTACTGGGTTTGATTGTCATCC	TTTCTCACTGAAACTTACCCAGTG
LMBR1-3	TTCAAGGGATTCAGAAACAGC	CGGTTGAATGGAAATGCTTC
RNF32-1	CACAGAAGTTGGGCCTCATT	TGCTAAACACCTGAGGACGA
RNF32-2	GCCTCCTCCTCAGTTCACAG	TGTGATCTCATGGCCACATT

图3 胎儿WES结果

图4 父母qPCR验证结果注：设计LMBR1基因3个区段、RNF32基因两个区段进行父母qPCR验证。结果显示胎儿7q36.3区域存在重复，该重复应为遗传自父亲，母亲未携带该重复。LMBR1-1为chr7:156619298-156619460，LMBR1-2为chr7:156516787-156516937，LMBR1-3为chr7:156476679-156476829，RNF32-1为chr7:156447269-156447422，RNF32-2为chr7:156468376-156468527。

表2 WES表型相关序列变异检测结果

基因	转录本	变异	遗传方式	基因型	东亚人群频率	ACMG分类	相关疾病（OMIM）
KIAA0586	NM_001329943.3	c.667C>T(p.R223C)	AR	杂合	0.001 1	意义不明确 (PM2_Suppporting)	短肋胸廓发育异常14型伴多指/趾畸形（616546）
BBS9	NM_198428.3	c.2509A>G(p.M837V)	AR	杂合	0.001 3	意义不明确 (PM2_Suppporting)	Bardet-Biedl综合征9型（615986）

图5 胎儿出生后双手影像学检查结果注：A 先证者右侧拇指多指与右侧拇指完全分开，无名指和小指并指。B 先证者左侧拇指多指并指，且左拇指外侧见一骨性突起，左手中指、无名指和小指并指。

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