Woodward Beth L, Lahiri Sudipta, Chauhan Anoop S, Garcia Marcos Rios, Goodley Lucy E, Clarke Thomas L, Pal Mohinder, Agathanggelou Angelo, Jhujh Satpal S, Ganesh Anil N, Hollins Fay M, Deforie Valentina Galassi, Maroofian Reza, Efthymiou Stephanie, Meinhardt Andrea, Mathew Christopher G, Simpson Michael A, Mefford Heather C, Faqeih Eissa A, Rosenzweig Sergio D, Volpi Stefano, Di Matteo Gigliola, Cancrini Caterina, Scardamaglia Annarita, Shackley Fiona, Davies E Graham, Ibrahim Shahnaz, Arkwright Peter D, Zaki Maha S, Stankovic Tatjana, Taylor A Malcolm R, Mazur Antonina J, Di Donato Nataliya, Houlden Henry, Rothenberg Eli, Stewart Grant S
Department of Cancer and Genomic Sciences, College of Medical and Health, University of Birmingham, Birmingham, UK.
Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA.
Nat Commun. 2025 May 14;16(1):4491. doi: 10.1038/s41467-025-59553-0.
DNA double strand break repair (DSBR) represents a fundamental process required to maintain genome stability and prevent the onset of disease. Whilst cell cycle phase and the chromatin context largely dictate which repair pathway is utilised to restore damaged DNA, it has been recently shown that nuclear actin filaments play a major role in clustering DNA breaks to facilitate DSBR by homologous recombination (HR). However, the mechanism with which nuclear actin and the different actin nucleating factors regulate HR is unclear. Interestingly, patients with biallelic mutations in the actin nucleating factor DIAPH1 exhibit a striking overlap of clinical features with the HR deficiency disorders, Nijmegen Breakage Syndrome (NBS) and Warsaw Breakage Syndrome (WABS). This suggests that DIAPH1 may play a role in regulating HR and that some of the clinical deficits associated with DIAPH1 mutations may be caused by an underlying DSBR defect. In keeping with this clinical similarity, we demonstrate that cells from DIAL (DIAPH1 Loss-of-function) Syndrome patients display an HR repair defect comparable to loss of NBS1. Moreover, we show that this DSBR defect is also observed in a subset of patients with Baraitser-Winter Cerebrofrontofacial (BWCFF) syndrome associated with mutations in ACTG1 (γ-actin) but not ACTB (β-actin). Lastly, we demonstrate that DIAPH1 and γ-actin promote HR-dependent repair by facilitating the relocalisation of the MRE11/RAD50/NBS1 complex to sites of DNA breaks to initiate end-resection. Taken together, these data provide a mechanistic explanation for the overlapping clinical symptoms exhibited by patients with DIAL syndrome, BWCFF syndrome and NBS.
DNA双链断裂修复（DSBR）是维持基因组稳定性和预防疾病发生所必需的基本过程。虽然细胞周期阶段和染色质环境在很大程度上决定了利用哪种修复途径来修复受损DNA，但最近研究表明，核肌动蛋白丝在聚集DNA断裂以促进通过同源重组（HR）进行的DSBR中起主要作用。然而，核肌动蛋白和不同的肌动蛋白成核因子调节HR的机制尚不清楚。有趣的是，肌动蛋白成核因子DIAPH1双等位基因突变的患者表现出与HR缺陷疾病尼曼-匹克氏综合征（NBS）和华沙断裂综合征（WABS）显著重叠的临床特征。这表明DIAPH1可能在调节HR中起作用，并且与DIAPH1突变相关的一些临床缺陷可能是由潜在的DSBR缺陷引起的。与这种临床相似性一致，我们证明来自DIAL（DIAPH1功能丧失）综合征患者的细胞表现出与NBS1缺失相当的HR修复缺陷。此外，我们表明，在与ACTG1（γ-肌动蛋白）而非ACTB（β-肌动蛋白）突变相关的巴赖特-温特脑额面部（BWCFF）综合征患者的一个亚组中也观察到这种DSBR缺陷。最后，我们证明DIAPH1和γ-肌动蛋白通过促进MRE11/RAD50/NBS1复合物重新定位到DNA断裂位点以启动末端切除来促进HR依赖性修复。综上所述，这些数据为DIAL综合征、BWCFF综合征和NBS患者表现出的重叠临床症状提供了一个机制解释。
