FRMD7 Mutations Disrupt the Interaction with GABRA2 and May Result in Infantile Nystagmus Syndrome
FRMD7 Mutations Disrupt the Interaction with GABRA2 and May Result in Infantile Nystagmus Syndrome
复制标题
FRMD7 突变破坏与 GABRA2 的相互作用，可能导致婴儿眼球震颤综合征
DOI：
10.1167/iovs.61.5.41
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发表时间：
2020-05-01
影响因子：
4.4
通讯作者：
Liu, Jing Yu
中科院分区：
文献类型：
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作者：
Jiang, Lei;Li, Yulei;Liu, Jing Yu
目的鉴定婴儿眼震综合征（INS）的致病基因，探讨FERM结构域7（FRMD 7）突变的致病机制。方法采用桑格测序法进行基因检测。Western blotting分析FRMD 7蛋白表达。进行Glucose S-转移酶下拉和免疫沉淀以研究与FRMD 7相互作用的蛋白质。在秀丽隐杆线虫中进行拯救测定以探索FRMD 7在体内的潜在作用。结果在3个中国X连锁INS家系中发现FRMD 7基因的一个重复突变和两个错义突变：c.998dupA/p.His333Glnfs*2、c.580G>A/p.Ala194Thr和c.973A>G/p.Arg325Gly（每个家系各1个）。三种突变体的表达水平与野生型FRMD 7在体外的表达水平相似。有趣的是，突变体p.His333Glnfs*2表现出主要的核定位，而野生型FRMD 7定位于细胞质。此外，我们发现FRMD 7直接与GABRA 2跨膜结构域3和4之间的环相互作用，GABRA 2是一种A型γ-氨基丁酸（GABA）受体（GABAARs）亚基，对受体转运和定位至关重要，而突变体p.Ala194Thr和p.Arg325Gly与GABRA 2的结合力降低。在frm-3（FRMD 7的线虫同源物）中，C.在elegans中，我们发现FRMD 7突变体对GABAARs光漂白后的运动缺陷和荧光恢复表现出较差的拯救效果。结论在3个X连锁INS家系中发现了3个FRMD 7突变体，证实GABRA 2是FRMD 7的新结合伴侣。这些发现表明FRMD 7通过靶向GABAAR发挥重要作用。
Purpose To identify the pathogenic gene of infantile nystagmus syndrome (INS) in three Chinese families and explore the potential pathogenic mechanism of FERM domain-containing 7 (FRMD7) mutations. Methods Genetic testing was performed via Sanger sequencing. Western blotting was used to analyze protein expression of FRMD7. Glutathione S-transferase pull-down and immunoprecipitation were conducted to investigate the proteins interacting with FRMD7. Rescue assays were performed in Caenorhabditis elegans to explore the potential role of FRMD7 in vivo. Results We recruited three Chinese families with X-linked INS and identified a duplication and two missense mutations in FRMD7: c.998dupA/p.His333Glnfs*2, c.580G>A/p.Ala194Thr, and c.973A>G/p.Arg325Gly (one in each family). Expression levels of three mutants were similar to that of wild-type FRMD7 in vitro. Interestingly, the mutant p.His333Glnfs*2 exhibited a predominantly nuclear location, whereas wild-type FRMD7 localized to the cytoplasm. In addition, we found FRMD7 to directly interact with the loop between transmembrane domains 3 and 4 of GABRA2, a type A gamma-aminobutyric acid (GABA) receptor (GABAARs) subunit critical for receptor transport and localization, whereas the mutants p.Ala194Thr and p.Arg325Gly exhibited decreased binding to GABRA2. In frm-3 (a nematode homologue of FRMD7) null C. elegans, we found that FRMD7 mutants exhibited a poor rescue effect on the defects of locomotion and fluorescence recovery after photobleaching of GABAARs. Conclusions Our findings identified three FRMD7 mutants in three Chinese families with X-linked INS and confirmed GABRA2 as a novel binding partner of FRMD7. These findings suggest that FRMD7 plays an important role by targeting GABAARs.