Characterization of a novel missense mutation in the prodomain of GDF5, which underlies brachydactyly type C and mild Grebe type chondrodysplasia in a large Pakistani family
Characterization of a novel missense mutation in the prodomain of GDF5, which underlies brachydactyly type C and mild Grebe type chondrodysplasia in a large Pakistani family
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DOI：
10.1007/s00439-013-1330-3
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发表时间：
2013-11-01
期刊：
影响因子：
5.3
通讯作者：
Shimomura, Yutaka
中科院分区：
文献类型：
--
作者：
Farooq, Muhammad;Nakai, Hiroyuki;Shimomura, Yutaka
所有TGF-β家族成员都有一个对分泌很重要的前结构域。已知缺乏TGF-β家族成员GDF 5的分泌是一些骨骼异常的基础，例如C型短指（趾）畸形，其特征在于巨大且无法解释的表型变异。为了寻找调节GDF 5分泌的潜在表型修饰剂，我们将过表达野生型（Wt）GDF 5和GDF 5的细胞与在患有C型短趾畸形和轻度Grebe型软骨发育不良（c527 T> C; p.Leu176 Pro）的巴基斯坦大家族中鉴定的前结构域中的新突变进行比较。最初的体外表达研究表明，p.Leu176Pro突变体（Mut）GDF 5不分泌到细胞外。我们随后发现GDF 5能够与潜在转化生长因子结合蛋白LTBP 1和LTBP 2形成复合物。此外，与Wt-GDF 5相比，在表达Mut-GDF 5的细胞中LTBP 1和LTBP 2的分泌严重受损。最后，我们证明了Wt-GDF 5的分泌被Mut-GDF 5抑制，但仅当LTBP（LTBP 1或LTBP 2）共表达时。基于这些发现，我们提出了一种新的模型，其中微环境中分泌辅因子或稳定蛋白如LTBP 1和LTBP 2的剂量可能会影响GDF 5分泌的程度，从而在GDF 5突变引起的表型中起修饰剂的作用。
All TGF-beta family members have a prodomain that is important for secretion. Lack of secretion of a TGF-beta family member GDF5 is known to underlie some skeletal abnormalities, such as brachydactyly type C that is characterized by a huge and unexplained phenotypic variability. To search for potential phenotypic modifiers regulating secretion of GDF5, we compared cells overexpressing wild type (Wt) GDF5 and GDF5 with a novel mutation in the prodomain identified in a large Pakistani family with Brachydactyly type C and mild Grebe type chondrodyslplasia (c527T > C; p.Leu176Pro). Initial in vitro expression studies revealed that the p.Leu176Pro mutant (Mut) GDF5 was not secreted outside the cells. We subsequently showed that GDF5 was capable of forming a complex with latent transforming growth factor binding proteins, LTBP1 and LTBP2. Furthermore, secretion of LTBP1 and LTBP2 was severely impaired in cells expressing the Mut-GDF5 compared to Wt-GDF5. Finally, we demonstrated that secretion of Wt-GDF5 was inhibited by the Mut-GDF5, but only when LTBP (LTBP1 or LTBP2) was co-expressed. Based on these findings, we suggest a novel model, where the dosage of secretory co-factors or stabilizing proteins like LTBP1 and LTBP2 in the microenvironment may affect the extent of GDF5 secretion and thereby function as modifiers in phenotypes caused by GDF5 mutations.