Cheng Fang, Song Wulian, Kang Yang, Yu Shihui, Yuan Huiping
Department of Ophthalmology, the 2nd Affiliated Hospital of Harbin Medical University, Harbin, China.
Mol Vis. 2011 Feb 10;17:448-55.
The paired box gene 6 (PAX6) on human chromosome 11p13 is an essential transcription factor for eye formation in animals. Mutations in PAX6 can lead to varieties of autosomal-dominant ocular malformations with aniridia as the major clinical signs. Known genetic alterations causing haplo-insufficiency of PAX6 include nonsense mutations, frame-shift mutations, splicing errors, or genomic deletions. The purpose of this study was to identify genetic defects as the underlying cause of familial aniridia in a large Chinese family.
All exons of PAX6 in the proband were sequenced by the Sanger sequencing technique. The genome of the proband was evaluated by a microarray-based comparative genomic hybridization (aCGH). Quantitative real-time PCR was applied to verify the abnormal aCGH findings in the proband and to test five other family members.
There were no detectable pathogenic mutations in the exons of PAX6 in the proband. The aCGH analysis showed two copies of PAX6 but revealed a 566 kb hemizygous deletion of chromosome 11p13, including four annotated genes doublecortin domain containing 1 (DCDC1), DnaJ homolog subfamily C member 24 (DNAJC24), IMP1 inner mitochondrial membrane(IMMP1L), andelongation factor protein 4 (ELP4) downstream of PAX6. Quantitative real-time PCR verified the deletion in the proband and further identified the deletion in a blind fashion in four affected family members but not in the one with a normal phenotype.
The 566 kb hemizygous deletion of chromosome 11p13 downstream of PAX6 should be the cause of the familial aniridia in this Chinese family, although two copies of PAX6 are intact. aCGH evaluation should be applied if there is a negative result for the mutation detection of PAX6 in patients with aniridia.
人类染色体11p13上的配对盒基因6（PAX6）是动物眼睛形成所必需的转录因子。PAX6突变可导致多种以无虹膜为主要临床症状的常染色体显性眼部畸形。已知导致PAX6单倍体不足的基因改变包括无义突变、移码突变、剪接错误或基因组缺失。本研究的目的是在一个大型中国家系中确定导致家族性无虹膜的遗传缺陷。
通过桑格测序技术对先证者PAX6的所有外显子进行测序。通过基于微阵列的比较基因组杂交（aCGH）评估先证者的基因组。应用定量实时PCR验证先证者aCGH的异常结果，并检测其他五名家庭成员。
先证者PAX6外显子中未检测到致病突变。aCGH分析显示有两个PAX6拷贝，但发现11p13染色体存在566 kb的半合子缺失，包括PAX6下游的四个注释基因：含双皮质素结构域1（DCDC1）、DnaJ同源亚家族C成员24（DNAJC24）、线粒体内膜IMP1（IMMP1L）和延伸因子蛋白4（ELP4）。定量实时PCR验证了先证者的缺失，并进一步盲目鉴定出四名患病家庭成员存在该缺失，而一名表型正常的家庭成员未出现该缺失。
尽管PAX6的两个拷贝完整，但PAX6下游11p13染色体566 kb的半合子缺失应是这个中国家系中家族性无虹膜的病因。对于无虹膜患者，如果PAX6突变检测结果为阴性，应进行aCGH评估。
