目的分析白内障－小角膜综合征(CCMC)一家系的临床特征和分子遗传学特点。
方法采用家系调查研究方法，收集2019年7月于厦门大学附属厦门眼科中心确诊的汉族CCMC一家系。详细询问病史，对家系中部分成员进行眼部检查，包括视力、眼压、裂隙灯显微镜、彩色眼底照相、眼部B型超声、角膜直径、眼前节光相干断层扫描、超声生物显微镜、角膜内皮镜及角膜地形图检查等。采集部分患者及家系成员外周血，提取DNA。对先证者DNA进行靶向高通量测序，所用芯片包含188个与晶状体异常相关的已知致病基因，在家系其他成员中应用Sanger测序对可疑位点进行检测，验证突变是否与临床表型共分离，明确该家系致病基因。采用蛋白功能预测软件REVEL对发现的变异位点进行生物信息学分析，评估该变异的致病性；采用InterPro分析蛋白保守结构域；采用ProtParam工具分析突变蛋白物理化学性质；采用PolyPhen-2在线软件预测突变蛋白的有害性；通过NCBI网站对致病基因的突变位点进行同源性分析，比较其在不同物种中的保守性。
结果该家系共4代39人，其中患者11例，符合常染色体显性遗传。临床表现为先天性白内障合并小角膜，其他眼部检查及全身系统性检查结果未见明显异常。基因检测结果显示先证者存在 CRYAA基因杂合变异c.61C>T，导致第21位氨基酸由精氨酸变异为色氨酸(p.Arg21Trp)，Sanger测序验证结果证实该杂合变异与疾病共分离。ProtParam分析显示该位点变异后蛋白产物阳离子基团总数减少，且亲水性及稳定性下降；PolyPhen-2在线软件预测为有害变异；同源性分析显示该变异位点对应的氨基酸序列在多物种中高度保守。
结论 CRYAA基因c.61C>T p．Arg21Trp可能是导致该家系发病的原因，为国内首次报道。
ObjectiveTo analyze the clinical and molecular genetic characteristics of a Chinese family with congenital cataract-microcornea syndrome.
MethodsThe method of pedigree investigation was adopted.A Chinese Han family with congenital cataract-microcornea syndrome was recruited in Xiamen Eye Center of Xiamen University.All the family members received detailed ophthalmologic examination including the best corrected visual acuity, intraocular pressure measurement by handheld applanation tonometry, slit lamp biomicroscopy, color fundus photography, B-scan ultrasonography, corneal diameter, anterior segment optical coherence tomography, ultrasound biomicroscopy, corneal endoscopy, and corneal topography.Genomic DNA was extracted from peripheral venous blood from some patients and unaffected family members.Targeted high-throughput DNA sequencing was performed on the proband.The sequencing chip contained 188 known pathogenic genes related to lens abnormalities.Suspected pathogenic genes were verified by Sanger sequencing in phenotypically normal family members to identify the co-segregation and the disease-causing gene.Bioinformatics analysis was performed to analyze the pathogenicity of variants by REVEL.Conserved protein domains were analyzed by InterPro.Physicochemical property of the mutant protein was analyzed by ProtParam.The deleteriousness of the protein was predicted by PolyPhen-2.Homology of the variants in pathogenic gene was analyzed by NCBI website to compare the conservation among various species.This study followed the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Xiamen Eye Center of Xiamen University (No.XMYKZX-LW-2009-003).Written informed consent was obtained from each subject prior to entering the study cohort.
ResultsThere were 39 members of 4 generations in this family including 11 patients with an autosomal dominant inheritance pattern.Clinical features of the patients included congenital cataract and microcornea.No obvious abnormality was found in ophthalmic and general examination.A heterozygous mutation c. 61C>T in the CRYAA gene was found, resulting in the mutation of the amino acid from arginine to tryptophan (p.Arg21Trp) at position 21, consistent with co-segregation.The number of cationic cluster in the mutant protein decreased, and the hydrophilicity and stability were reduced.The variant was predicted to be deleterious and was highly conserved in multiple species.
ConclusionsA novel heterozygous mutation c.61C>T p. Arg21Trp in CRYAA gene is considered as the causal gene of this family.It is the first time this variant has been reported in China.
张达人,卢岚,曾杰,等. 中国白内障－小角膜综合征一家系突变基因及表型分析[J]. 中华实验眼科杂志,2022,40(10)：955-959.
DOI:10.3760/cma.j.cn115989-20200224-00099版权归中华医学会所有。
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除非特别声明，本刊刊出的所有文章不代表中华医学会和本刊编委会的观点。
张达人、卢岚：参与选题、酝酿和设计试验、论文撰写及修改；曾杰：参与实施研究、采集数据；李丹丽、王云、王希振、樊宁：分析/解释数据、对文章知识性内容的审阅；黄瓅：参与论文撰写及修改；刘旭阳：参与论文选题、酝酿和设计试验、论文定稿
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