Tompson Stuart W, Johnson Charles, Abbott Diana, Bakall Benjamin, Soler Vincent, Yanovitch Tammy L, Whisenhunt Kristina N, Klemm Thomas, Rozen Steve, Stone Edwin M, Johnson Max, Young Terri L
a Department of Ophthalmology and Visual Sciences , University of Wisconsin - Madison , Madison , Wisconsin , USA.
b Retina Consultants, Ltd ., Fargo , North Dakota , USA.
Ophthalmic Genet. 2017 Jan-Feb;38(1):43-50. doi: 10.1080/13816810.2016.1275018. Epub 2017 Jan 17.
In a four-generation Caucasian family variably diagnosed with autosomal dominant (AD) Stickler or Wagner disease, commercial gene screening failed to identify a mutation in COL2A1 or VCAN. We utilized linkage mapping and exome sequencing to identify the causal variant.
Genomic DNA samples collected from 40 family members were analyzed. A whole-genome linkage scan was performed using Illumina HumanLinkage-24 BeadChip followed by two-point and multipoint linkage analyses using FASTLINK and MERLIN. Exome sequencing was performed on two affected individuals, followed by co-segregation analysis.
Parametric multipoint linkage analysis using an AD inheritance model demonstrated HLOD scores > 2.00 at chromosomes 1p36.13-1p36.11 and 12q12-12q14.1. SIMWALK multipoint analysis replicated the peak in chromosome 12q (peak LOD = 1.975). FASTLINK two-point analysis highlighted several clustered chromosome 12q SNPs with HLOD > 1.0. Exome sequencing revealed a novel nonsense mutation (c.115C>T, p.Gln39*) in exon 2 of COL2A1 that is expected to result in nonsense-mediated decay of the RNA transcript. This mutation co-segregated with all clinically affected individuals and seven individuals who were clinically unaffected.
The utility of combining traditional linkage mapping and exome sequencing is highlighted to identify gene mutations in large families displaying a Mendelian inheritance of disease. Historically, nonsense mutations in exon 2 of COL2A1 have been reported to cause a fully penetrant ocular-only Stickler phenotype with few or no systemic manifestations. We report a novel nonsense mutation in exon 2 of COL2A1 that displays incomplete penetrance and/or variable age of onset with extraocular manifestations.
在一个四代高加索家族中，该家族被诊断患有常染色体显性（AD）遗传性斯迪克勒病或瓦格纳病，但商业基因筛查未能在COL2A1或VCAN基因中发现突变。我们利用连锁图谱和外显子测序来确定致病变异。
对从40名家族成员收集的基因组DNA样本进行分析。使用Illumina HumanLinkage-24 BeadChip进行全基因组连锁扫描，随后使用FASTLINK和MERLIN进行两点和多点连锁分析。对两名受影响个体进行外显子测序，随后进行共分离分析。
使用AD遗传模型进行的参数化多点连锁分析显示，在染色体1p36.13 - 1p36.11和12q12 - 12q14.1处的HLOD分数> 2.00。SIMWALK多点分析在染色体12q处重复出现峰值（峰值LOD = 1.975）。FASTLINK两点分析突出显示了几个聚集在染色体12q上的单核苷酸多态性（SNP），其HLOD > 1.0。外显子测序揭示了COL2A1基因第2外显子中的一个新的无义突变（c.115C>T，p.Gln3*），预计该突变会导致RNA转录本的无义介导衰变。该突变与所有临床受影响个体以及7名临床未受影响个体共分离。
强调了结合传统连锁图谱和外显子测序在确定表现出孟德尔疾病遗传的大家族中的基因突变的实用性。历史上，据报道COL2A1基因第2外显子中的无义突变会导致仅累及眼部的完全显性斯迪克勒表型，几乎没有或没有全身表现。我们报告了COL2A1基因第2外显子中的一个新的无义突变，该突变表现出不完全显性和/或可变的发病年龄，并伴有眼外表现。
