Usher Syndrome Belongs to the Genetic Diseases Associated with Radiosensitivity: Influence of the ATM Protein Kinase

Abstract

Usher syndrome (USH) is a rare autosomal recessive disease characterized by the combination of hearing loss, visual impairment due to retinitis pigmentosa, and in some cases vestibular dysfunctions. Studies published in the 1980s reported that USH is associated with cellular radiosensitivity. However, the molecular basis of this particular phenotype has not yet been documented. The aim of this study was therefore to document the radiosensitivity of USH1—a subset of USH—by examining the radiation-induced nucleo-shuttling of ATM (RIANS), as well as the functionality of the repair and signaling pathways of the DNA double-strand breaks (DSBs) in three skin fibroblasts derived from USH1 patients. The clonogenic cell survival, the micronuclei, the nuclear foci formed by the phosphorylated forms of the X variant of the H2A histone (ɣH2AX), the phosphorylated forms of the ATM protein (pATM), and the meiotic recombination 11 nuclease (MRE11) were used as cellular and molecular endpoints. The interaction between the ATM and USH1 proteins was also examined by proximity ligation assay. The results showed that USH1 fibroblasts were associated with moderate but significant radiosensitivity, high yield of micronuclei, and impaired DSB recognition but normal DSB repair, likely caused by a delayed RIANS, suggesting a possible sequestration of ATM by some USH1 proteins overexpressed in the cytoplasm. To our knowledge, this report is the first radiobiological characterization of cells from USH1 patients at both molecular and cellular scales.

Quantitative Correlations between Radiosensitivity Biomarkers Show That the ATM Protein Kinase Is Strongly Involved in the Radiotoxicities Observed after Radiotherapy

“…Micronuclei lead to irreversibly damaged chromosomal fragments causing mitotic death [ 51 ]. Micronuclei have been shown to be quantitatively correlated with cellular radiosensitivity when assessed by the clonogenic cell survival assay [ 28 , 52 , 53 , 54 ]. However, to our knowledge, such cytogenetic endpoints have not yet been tested in a large spectrum of CTCAE grades, with the notable exception of our previous report gathering 117 COPERNIC cell lines [ 43 ].…”

“…The clonogenic cell survival assay has been also applied to a number of non-tumor cellular models, notably lymphoblasts and fibroblasts [ 26 , 27 , 71 ]; in 1975, Taylor et al pointed out, for the first time with the clonogenic cell survival assay, the extreme radiosensitivity associated with ataxia telangiectasia ( ATM mutations) [ 45 ]. After this discovery, a considerable number of studies have reported the radiobiological characterization of various genetic syndromes which permits to propose, to date, a complete view of human radiosensitivity [ 22 , 52 , 53 , 54 , 72 , 73 , 74 , 75 , 76 ]. Conversely, with regard to the radiobiological characterization of cells provided from OR patients, there are a few reports about the link between clonogenic cell survival data and the CTCAE grade.…”

Cancer and Radiosensitivity Syndromes: Is Impaired Nuclear ATM Kinase Activity the Primum Movens?

“…Nevertheless, in cells that show moderate but significant radiosensitivity, RIANS is delayed by the overexpression of cytoplasmic substrates of ATM, which sequestrate the RI ATM monomers in the cytoplasm. Such a model was confirmed by both immunoblots and proximity ligation assays [ 20 , 21 , 246 ]. These ATM substrates, called X-proteins, are generally the proteins mutated specifically in the syndrome considered [ 5 , 8 , 18 , 20 , 21 ] ( Figure 3 ).…”

Disease Resistance and Molecular Variations in Irradiation Induced Mutants of Two Pea Cultivars

“…The explanations might be that the number of M 3 mutants was small, or the radiosensitivity of this cultivar was weaker than that of CW8. The difference in radiosensitivity, influenced by genetics, existed in various cultivars of the same crop [ 45 , 46 ].…”