Laboratory for Bone and Joint Diseases, Center for Genomic Medicine, 4-6-1 Shirokane-dai, Minato-ku, Tokyo 108-8639, Japan.
J Med Genet. 2010 Oct;47(10):704-9. doi: 10.1136/jmg.2009.075358. Epub 2010 Jun 24.
Mutations in TRPV4, a gene that encodes a Ca(2+) permeable non-selective cation channel, have recently been found in a spectrum of skeletal dysplasias that includes brachyolmia, spondylometaphyseal dysplasia, Kozlowski type (SMDK) and metatropic dysplasia (MD). Only a total of seven missense mutations were detected, however. The full spectrum of TRPV4 mutations and their phenotypes remained unclear.
To examine TRPV4 mutation spectrum and phenotype-genotype association, we searched for TRPV4 mutations by PCR-direct sequencing from genomic DNA in 22 MD and 20 SMDK probands.
TRPV4 mutations were found in all but one MD subject. In total, 19 different heterozygous mutations were identified in 41 subjects; two were recurrent and 17 were novel. In MD, a recurrent P799L mutation was identified in nine subjects, as well as 10 novel mutations including F471del, the first deletion mutation of TRPV4. In SMDK, a recurrent R594H mutation was identified in 12 subjects and seven novel mutations. An association between the position of mutations and the disease phenotype was also observed. Thus, P799 in exon 15 is a hot codon for MD mutations, as four different amino acid substitutions have been observed at this codon; while R594 in exon 11 is a hotspot for SMDK mutations.
The TRPV4 mutation spectrum in MD and SMDK, which showed genotype-phenotype correlation and potential functional significance of mutations that are non-randomly distributed over the gene, was presented in this study. The results would help diagnostic laboratories establish efficient screening strategies for genetic diagnosis of the TRPV4 dysplasia family diseases.
TRPV4 是一种编码 Ca(2+) 通透性非选择性阳离子通道的基因，最近在一系列骨骼发育不良症中发现了基因突变，包括短肢畸形、脊椎干骺端发育不良、Kozlowski 型（SMDK）和变形性骨炎（MD）。然而，仅检测到总共 7 个错义突变。TRPV4 突变的全貌及其表型仍不清楚。
为了检查 TRPV4 突变谱及其表型-基因型相关性，我们通过聚合酶链反应直接测序从 22 名 MD 和 20 名 SMDK 先证者的基因组 DNA 中寻找 TRPV4 突变。
除了一名 MD 患者外，所有患者均发现 TRPV4 突变。在 41 名受试者中总共鉴定出 19 种不同的杂合突变；其中两个是反复出现的，17 个是新的。在 MD 中，在 9 名患者中发现了一个反复出现的 P799L 突变，以及 10 个新的突变，包括 F471del，这是 TRPV4 的第一个缺失突变。在 SMDK 中，在 12 名患者中发现了一个反复出现的 R594H 突变，以及 7 个新的突变。还观察到突变位置与疾病表型之间的关联。因此，exon 15 中的 P799 是 MD 突变的热点密码子，因为在这个密码子已经观察到四个不同的氨基酸取代；而 exon 11 中的 R594 是 SMDK 突变的热点。
本研究提出了 MD 和 SMDK 中 TRPV4 突变谱，该谱显示了基因型-表型相关性和突变的潜在功能意义，这些突变在基因中是非随机分布的。结果将有助于诊断实验室建立有效的遗传诊断 TRPV4 发育不良家族疾病的筛选策略。
