Kloeckener-Gruissem Barbara, Bartholdi Deborah, Abdou Marie-Therese, Zimmermann Dieter R, Berger Wolfgang
Division of Medical Molecular Genetics and Gene Diagnostics, University of Zurich, Zurich, Switzerland.
Mol Vis. 2006 Apr 17;12:350-5.
The aim of the present study was to determine the genetic defect in Wagner syndrome, a rare disorder belonging to the group of hereditary vitreoretinal degenerations. This disease has been genetically mapped to chromosome 5q14.3.
Molecular analysis was performed in the progeny of the original pedigree described by Wagner in 1938. We searched for pathogenic mutations and their effects in two candidate genes, CSPG2 and EDIL3, which locate to the critical chromosomal interval. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis was used to investigate potential splice defects of CSPG2 transcripts.
While no alterations were detected in the exons of EDIL3, several changes were identified in the CSPG2 gene. Only one of the novel changes, a heterozygous G to A substitution of the first nucleotide in intron 8, cosegregates with the disease phenotype. This change disrupts the highly conserved splice donor sequence. In blood cells of an index patient, we found CSPG2 transcripts with normally spliced exon 8/9 junction but also two additional CSPG2 transcripts, which were not detected in the control. One lacks the entire exon 8, while the other is missing only the last 21 bp of exon 8.
CSPG2 encodes versican, a large proteoglycan, which is an extracellular matrix component of the human vitreous and participates in the formation of the vitreous gel. The splice site mutation described here may lead to a complete lack of exon 8 in CSPG2 transcripts, which shortens the predicted protein by 1754 amino acids and leads to severe reduction of glycosaminoglycan attachment sites.
本研究旨在确定瓦格纳综合征的基因缺陷，该综合征是一种罕见的遗传性玻璃体视网膜变性疾病。该疾病已在基因上定位到5号染色体q14.3区域。
对1938年瓦格纳描述的原始家系的后代进行分子分析。我们在位于关键染色体区间的两个候选基因CSPG2和EDIL3中寻找致病突变及其影响。采用逆转录聚合酶链反应（RT-PCR）分析来研究CSPG2转录本潜在的剪接缺陷。
虽然在EDIL3的外显子中未检测到改变，但在CSPG2基因中发现了几处变化。只有其中一个新变化，即内含子8中第一个核苷酸由杂合的G突变为A，与疾病表型共分离。这种变化破坏了高度保守的剪接供体序列。在一名索引患者的血细胞中，我们发现了具有正常剪接的外显子8/9连接的CSPG2转录本，但也发现了另外两种在对照中未检测到的CSPG2转录本。一种缺失了整个外显子8，而另一种仅缺失外显子8的最后21个碱基对。
CSPG2编码多功能蛋白聚糖versican，它是人类玻璃体的细胞外基质成分，并参与玻璃体凝胶的形成。此处描述的剪接位点突变可能导致CSPG2转录本完全缺失外显子8，这使得预测的蛋白质缩短了1754个氨基酸，并导致糖胺聚糖附着位点严重减少。
