Cell Biology Program, Hospital for Sick Children, Toronto, ON, Canada.
Department of Biochemistry, University of Toronto, Toronto, ON, Canada.
FASEB J. 2020 Dec;34(12):16516-16535. doi: 10.1096/fj.202001178R. Epub 2020 Oct 30.
Primary cilia are critical hubs for several signaling pathways, and defects in ciliogenesis or cilia maintenance produce a range of diseases collectively known as ciliopathies. Ciliogenesis requires vesicle trafficking along a network of microtubules and actin filaments to the basal body. The DIAPH1 (Diaphanous-related formin) family of formins promotes both actin polymerization and EB1-dependent microtubule (MT) stability. EB1 and EB3 have previously been implicated in cilia biogenesis to carry out centrosome-related functions. However, the role of DIAPH1 proteins had not been examined. Here we show that the depletion of DIAPH1 decreased ciliogenesis, cilia length, and reduced trafficking within cilia. Additionally, both actin nucleating and microtubule-stabilizing properties of DIAPH1 are important for their cilia functions. To assess their roles in ciliogenesis in isolation, we targeted DIAPH1 specifically to the basal body, which caused an increase in cilia length and increased trafficking within cilia. Intriguingly, expression of DIAPH1 mutants associated with human deafness and microcephaly impaired ciliation and caused cilia elongation and bulb formation. These results suggest that the actin and microtubule functions of DIAPH1 proteins regulate cilia maintenance in part by regulating vesicular trafficking to the base of the primary cilia.
原发性纤毛是几种信号通路的关键枢纽，纤毛发生或纤毛维持的缺陷会导致一系列被称为纤毛病的疾病。纤毛发生需要沿着微管和肌动蛋白丝网络向基体运输囊泡。formin 家族的 DIAPH1（隔膜相关形成蛋白）促进肌动蛋白聚合和 EB1 依赖性微管 (MT) 稳定性。EB1 和 EB3 先前被牵连到纤毛发生中，以执行中心体相关功能。然而，DIAPH1 蛋白的作用尚未被检测到。在这里，我们表明 DIAPH1 的耗竭会减少纤毛发生、纤毛长度，并减少纤毛内的运输。此外，DIAPH1 的肌动蛋白成核和微管稳定特性对于它们的纤毛功能很重要。为了单独评估它们在纤毛发生中的作用，我们将 DIAPH1 特异性靶向基体，这导致纤毛长度增加，并增加了纤毛内的运输。有趣的是，与人类耳聋和小头畸形相关的 DIAPH1 突变体的表达会损害纤毛形成，并导致纤毛伸长和球形成。这些结果表明，DIAPH1 蛋白的肌动蛋白和微管功能通过调节囊泡向初级纤毛基部的运输来部分调节纤毛的维持。
