Área de Genética, Facultad de Medicina/Instituto de Investigación en Discapacidades Neurológicas, Universidad de Castilla-La Mancha, Albacete, Spain.
Ophthalmology. 2013 Apr;120(4):716-23. doi: 10.1016/j.ophtha.2012.09.016. Epub 2012 Dec 4.
To assess the mutation spectrum, enzymatic activity, and phenotypic features associated with CYP1B1 genotypes in primary congenital glaucoma (PCG) and nondominant juvenile glaucoma (ndJG).
CYP1B1 genotyping, segregation analysis, and functional evaluation of mutations in a cohort of patients.
A total of 177 probands clinically diagnosed with PCG (161) or ndJG (16).
Automatic DNA sequencing of the promoter (-1 to -867) and the 3 CYP1B1 exons. CYP1B1 enzymatic activity was evaluated using an ethoxyresorufin O-deethylation assay in transfected HEK-293T cells.
Screening and functional evaluation of CYP1B1 mutations. Glaucoma diagnosis based on slit-lamp examination, measurement of intraocular pressure, gonioscopy, and fundus examination.
Thirty-one different mutations were identified in 56 PCG and 7 ndJG index cases. To the best of our knowledge, 3 of the identified mutations were novel (-337G>T, F123L, and I399_P400del). Approximately 56% of all mutation carriers were compound heterozygotes, 25% were homozygotes, and both groups inherited glaucoma as an autosomal recessive trait. Nineteen percent of carriers were heterozygotes and showed non-Mendelian segregation. In vitro and inferred functional analysis showed that no less than approximately 74% of the recessive genotypes result in null enzymatic activity. We detected variable expressivity in relation to age of onset and a possible case of incomplete penetrance in 3 of 6 families (50%), with more than 1 affected child or more than 1 subject carrying 2 CYP1B1 mutant alleles. Altogether, these data support that PCG is not a simple monogenic disease. In addition, most patients with PCG carrying null or putative null genotypes showed severe bilateral phenotypes featured by early disease onset, frequently at birth. The mean number of trabeculectomies per eye was significantly higher in carriers than in noncarriers.
This is the largest analysis of CYP1B1 mutations performed in European patients with PCG to date. Our data show that null CYP1B1 genotypes, and therefore complete absence of CYP1B1 activity, frequently lead to severe phenotypes. Our results support that CYP1B1 glaucoma is not a simple monogenic disease and that CYP1B1 activity levels could influence the phenotype.
评估 CYP1B1 基因型与原发性先天性青光眼（PCG）和非优势青少年型青光眼（ndJG）相关的突变谱、酶活性和表型特征。
对患者队列进行 CYP1B1 基因分型、分离分析和突变的功能评估。
共 177 名临床诊断为 PCG（161 名）或 ndJG（16 名）的先证者。
自动 DNA 测序启动子（-1 至-867）和 3 个 CYP1B1 外显子。在转染的 HEK-293T 细胞中使用 ethoxyresorufin O-脱乙基化测定法评估 CYP1B1 酶活性。
CYP1B1 突变的筛查和功能评估。根据裂隙灯检查、眼压测量、房角镜检查和眼底检查进行青光眼诊断。
在 56 例 PCG 和 7 例 ndJG 索引病例中发现了 31 种不同的突变。据我们所知，鉴定出的 3 种突变是新的（-337G>T、F123L 和 I399_P400del）。所有突变携带者中约有 56%为复合杂合子，25%为纯合子，两组均以常染色体隐性遗传方式遗传青光眼。19%的携带者为杂合子，且表现出非孟德尔分离。体外和推断的功能分析表明，至少约 74%的隐性基因型导致酶活性完全缺失。我们发现与发病年龄有关的可变表达，并在 6 个家族中的 3 个（50%）中发现可能存在不完全外显，有 1 个以上受影响的孩子或有 2 个 CYP1B1 突变等位基因的 1 个以上个体。总的来说，这些数据支持 PCG 不是一种简单的单基因疾病。此外，大多数携带无功能或推定无功能基因型的 PCG 患者表现出严重的双侧表型，发病早，常在出生时。携带者每只眼行小梁切除术的平均次数明显高于非携带者。
这是迄今为止对欧洲 PCG 患者进行的最大 CYP1B1 突变分析。我们的数据表明，无功能 CYP1B1 基因型，因此完全缺乏 CYP1B1 活性，常导致严重的表型。我们的结果支持 CYP1B1 青光眼不是一种简单的单基因疾病，CYP1B1 活性水平可能影响表型。
