Bunn Kieran J, Daniel Phil, Rösken Heleen S, O'Neill Adam C, Cameron-Christie Sophia R, Morgan Tim, Brunner Han G, Lai Angeline, Kunst Henricus P M, Markie David M, Robertson Stephen P
Department of Women's and Children's Health, Dunedin School of Medicine, University of Otago, Dunedin 9054, New Zealand.
Department of Human Genetics, Radboud University Medical Center, Nijmegen 6525 GA, the Netherlands; Department of Clinical Genetics, Maastricht University Medical Center, Maastricht 6200 MD, the Netherlands.
Am J Hum Genet. 2015 Apr 2;96(4):623-30. doi: 10.1016/j.ajhg.2015.02.010. Epub 2015 Mar 26.
Robinow syndrome (RS) is a phenotypically and genetically heterogeneous condition that can be caused by mutations in genes encoding components of the non-canonical Wnt signaling pathway. In contrast, germline mutations that act to increase canonical Wnt signaling lead to distinctive osteosclerotic phenotypes. Here, we identified de novo frameshift mutations in DVL1, a mediator of both canonical and non-canonical Wnt signaling, as the cause of RS-OS, an RS subtype involving osteosclerosis, in three unrelated individuals. The mutations all delete the DVL1 C terminus and replace it, in each instance, with a novel, highly basic sequence. We showed the presence of mutant transcript in fibroblasts from one individual with RS-OS and demonstrated unimpaired protein stability with transfected GFP-tagged constructs bearing a frameshift mutation. In vitro TOPFlash assays, in apparent contradiction to the osteosclerotic phenotype, revealed that the mutant allele was less active than the wild-type allele in the canonical Wnt signaling pathway. However, when the mutant and wild-type alleles were co-expressed, canonical Wnt activity was 2-fold higher than that in the wild-type construct alone. This work establishes that DVL1 mutations cause a specific RS subtype, RS-OS, and that the osteosclerosis associated with this subtype might be the result of an interaction between the wild-type and mutant alleles and thus lead to elevated canonical Wnt signaling.
罗宾诺综合征（RS）是一种在表型和基因上具有异质性的疾病，可由编码非经典Wnt信号通路成分的基因突变引起。相比之下，能够增加经典Wnt信号传导的种系突变会导致独特的骨硬化表型。在这里，我们在三个无亲缘关系的个体中，鉴定出DVL1（经典和非经典Wnt信号传导的介质）中的新生移码突变是RS-OS（一种涉及骨硬化的RS亚型）的病因。这些突变均删除了DVL1的C末端，并在每种情况下用一个新的、高度碱性的序列取代它。我们在一名患有RS-OS的个体的成纤维细胞中检测到了突变转录本，并通过转染带有移码突变的GFP标记构建体证明了蛋白质稳定性未受影响。在体外TOPFlash试验中，与骨硬化表型明显矛盾的是，显示突变等位基因在经典Wnt信号通路中的活性低于野生型等位基因。然而，当突变等位基因和野生型等位基因共表达时，经典Wnt活性比单独的野生型构建体高2倍。这项工作证实，DVL1突变导致了一种特定的RS亚型，即RS-OS，并且与该亚型相关的骨硬化可能是野生型和突变等位基因之间相互作用的结果，从而导致经典Wnt信号传导升高。
