The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben-Gurion University of the Negev, 84105, Beer Sheva, Israel.
Department of Ophthalmology, Soroka Medical Center and Clalit Health Services, Faculty of Health Sciences, Ben-Gurion University, 84101, Beer Sheva, Israel.
Eur J Hum Genet. 2019 Jun;27(6):928-940. doi: 10.1038/s41431-019-0347-z. Epub 2019 Feb 5.
Studies of ciliopathies have served in elucidating much of our knowledge of structure and function of primary cilia. We report humans with Bardet-Biedl syndrome who display intellectual disability, retinitis pigmentosa, obesity, short stature and brachydactyly, stemming from a homozyogous truncation mutation in SCAPER, a gene previously associated with mitotic progression. Our findings, based on linkage analysis and exome sequencing studies of two remotely related large consanguineous families, are in line with recent reports of SCAPER variants associated with intellectual disability and retinitis pigmentosa. Using immuno-fluorescence and live cell imaging in NIH/3T3 fibroblasts and SH-SY5Y neuroblastoma cell lines over-expressing SCAPER, we demonstrate that both wild type and mutant SCAPER are expressed in primary cilia and co-localize with tubulin, forming bundles of microtubules. While wild type SCAPER was rarely localized along the ciliary axoneme and basal body, the aberrant protein remained sequestered to the cilia, mostly at the ciliary tip. Notably, longer cilia were demonstrated both in human affected fibroblasts compared to controls, as well as in NIH/3T3 cells transfected with mutant versus wildtype SCAPER. As SCAPER expression is known to peak at late G1 and S phase, overlapping the timing of ciliary resorption, our data suggest a possible role of SCAPER in ciliary dynamics and disassembly, also affecting microtubule-related mitotic progression. Thus, we outline a human ciliopathy syndrome and demonstrate that it is caused by a mutation in SCAPER, affecting primary cilia.
纤毛病的研究有助于阐明我们对初级纤毛结构和功能的许多认识。我们报告了两例具有 Bardet-Biedl 综合征的患者，他们表现为智力障碍、视网膜色素变性、肥胖、身材矮小和短指（趾）畸形，这是由于 SCAPER 基因的纯合截断突变引起的，该基因先前与有丝分裂进展有关。我们的发现基于两个远距离相关的大型近亲家族的连锁分析和外显子组测序研究，与最近报道的与智力障碍和视网膜色素变性相关的 SCAPER 变体一致。使用免疫荧光和活细胞成像在过表达 SCAPER 的 NIH/3T3 成纤维细胞和 SH-SY5Y 神经母细胞瘤细胞系中，我们证明野生型和突变型 SCAPER 均在初级纤毛中表达，并与微管蛋白共定位，形成微管束。虽然野生型 SCAPER 很少沿纤毛轴丝和基底体定位，但异常蛋白仍然被隔离在纤毛中，主要位于纤毛尖端。值得注意的是，与对照相比，受影响的人成纤维细胞中的纤毛更长，以及转染突变型与野生型 SCAPER 的 NIH/3T3 细胞中的纤毛也更长。由于已知 SCAPER 的表达在 G1 晚期和 S 期达到峰值，与纤毛收缩的时间重叠，我们的数据表明 SCAPER 可能在纤毛动力学和解体中发挥作用，也影响与微管相关的有丝分裂进展。因此，我们概述了一种人类纤毛病综合征，并证明它是由 SCAPER 突变引起的，影响初级纤毛。
