Goetz Sarah C, Bangs Fiona, Barrington Chloe L, Katsanis Nicholas, Anderson Kathryn V
Program in Developmental Biology, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, 1275 York Ave. New York, United States of America.
Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, United States of America.
PLoS One. 2017 Mar 14;12(3):e0173399. doi: 10.1371/journal.pone.0173399. eCollection 2017.
The importance of primary cilia in human health is underscored by the link between ciliary dysfunction and a group of primarily recessive genetic disorders with overlapping clinical features, now known as ciliopathies. Many of the proteins encoded by ciliopathy-associated genes are components of a handful of multi-protein complexes important for the transport of cargo to the basal body and/or into the cilium. A key question is whether different complexes cooperate in cilia formation, and whether they participate in cilium assembly in conjunction with intraflagellar transport (IFT) proteins. To examine how ciliopathy protein complexes might function together, we have analyzed double mutants of an allele of the Meckel syndrome (MKS) complex protein MKS1 and the BBSome protein BBS4. We find that Mks1; Bbs4 double mutant mouse embryos exhibit exacerbated defects in Hedgehog (Hh) dependent patterning compared to either single mutant, and die by E14.5. Cells from double mutant embryos exhibit a defect in the trafficking of ARL13B, a ciliary membrane protein, resulting in disrupted ciliary structure and signaling. We also examined the relationship between the MKS complex and IFT proteins by analyzing double mutant between Mks1 and a hypomorphic allele of the IFTB component Ift172. Despite each single mutant surviving until around birth, Mks1; Ift172avc1 double mutants die at mid-gestation, and exhibit a dramatic failure of cilia formation. We also find that Mks1 interacts genetically with an allele of Dync2h1, the IFT retrograde motor. Thus, we have demonstrated that the MKS transition zone complex cooperates with the BBSome to mediate trafficking of specific trans-membrane receptors to the cilium. Moreover, the genetic interaction of Mks1 with components of IFT machinery suggests that the transition zone complex facilitates IFT to promote cilium assembly and structure.
原发性纤毛在人类健康中的重要性通过纤毛功能障碍与一组主要为隐性遗传疾病（临床表现重叠，现称为纤毛病）之间的联系得以凸显。许多与纤毛病相关基因编码的蛋白质是少数几种多蛋白复合物的组成部分，这些复合物对于货物向基体和/或纤毛内的运输很重要。一个关键问题是不同的复合物在纤毛形成过程中是否协同作用，以及它们是否与鞭毛内运输（IFT）蛋白一起参与纤毛组装。为了研究纤毛病蛋白复合物如何共同发挥作用，我们分析了梅克尔综合征（MKS）复合物蛋白MKS1的一个等位基因与BBSome蛋白BBS4的双突变体。我们发现，与任一单突变体相比，Mks1; Bbs4双突变小鼠胚胎在刺猬信号通路（Hh）依赖性模式形成中表现出更严重的缺陷，并在E14.5时死亡。双突变胚胎的细胞在纤毛膜蛋白ARL13B的运输方面存在缺陷，导致纤毛结构和信号传导中断。我们还通过分析Mks1与IFTB组件Ift172的一个低表达等位基因之间的双突变体，研究了MKS复合物与IFT蛋白之间的关系。尽管每个单突变体都能存活到出生左右，但Mks1; Ift172avc1双突变体在妊娠中期死亡，并表现出明显的纤毛形成失败。我们还发现Mks1与IFT逆行马达Dync2h1的一个等位基因存在遗传相互作用。因此，我们证明了MKS过渡区复合物与BBSome协同作用，介导特定跨膜受体向纤毛的运输。此外，Mks1与IFT机制组件的遗传相互作用表明，过渡区复合物促进IFT以促进纤毛组装和结构形成。
