Association of Copresence of Pathogenic Variants Related to Amyotrophic Lateral Sclerosis and Prognosis
Adriano Chiò, Cristina Moglia, Antonio Canosa, Umberto Manera, Maurizio Grassano, Rosario Vasta, Francesca Palumbo, Salvatore Gallone, Maura Brunetti, Marco Barberis, Fabiola De Marchi, Clifton L. Dalgard, Ruth Chia, Gabriele Mora, Barbara Iazzolino, Laura Peotta, Bryan J. Traynor, Lucia Corrado, Sandra D’Alfonso, Letizia Mazzini, Andrea Calvo
Abstract
<h3>Objective.</h3> Despite recent advances, it is not clear whether the various genes/genetic variants related to ALS interact in modifying patients phenotype. The aim of this study was to determine if the co-presence of genetic variants related to ALS has interactive effects on the course of the disease. <h3>Methods.</h3> The study population includes 1,245 ALS patients identified through the Piemonte Register for ALS between 2007 and 2016 and not carrying <i>SOD1, TARDBP</i> and <i>FUS</i> pathogenic variants. Controls were 766 Italian subjects age-, sex-, and geographically-matched to cases. We considered <i>UNC13A (</i>rs12608932)<i>, CAMTA1 (</i>rs2412208)<i>, SLC11A2 (</i>rs407135) and <i>ZNF512B (</i>rs2275294<i>)</i> variants, as well as <i>ATXN2</i> polyQ intermediate repeats (≥31) and <i>C9orf72</i> GGGGCC intronic expansions( ≥30). <h3>Results.</h3> The median survival time of the whole cohort was 2.67 years (IQR 1.67-5.25). In univariate analysis only <i>C9orf72</i> (2.51 years, IQR 1.74-3.82; p=0.016), <i>ATXN2</i> (1.82 years, IQR 1.08-2.33; p<0.001) and <i>UNC13A</i><sup><i>C/C</i></sup> (2.3 years, IQR 1.3-3.9; p<0.001) significantly reduced survival. In Cox multivariable analysis, also <i>CAMTA1</i> emerged to be independently related to survival (HR 1.13, 95% c.i. 1.001-1.30, p=0.048). The co-presence of two detrimental alleles/expansions was correlated with shorter survival. In particular, the median survival of patients with <i>CAMTA1</i><sup>G/G+G/T</sup> and <i>UNC13A</i><sup>C/C</sup> alleles was 1.67 years (1.16-3.08) years compared to 2.75 years (1.67-5.26) of the patients not carrying these variants (p<0.001); the survival of patients with <i>CAMTA1</i><sup>G/G+G/T</sup> alleles and <i>ATXN2</i><sup>≥31</sup> intermediate polyQ repeats was 1.75 years (0.84-2.18) (p<0.001); the survival of patients with <i>ATXN2</i><sup>≥31</sup> polyQ repeats and <i>UNC13A</i><sup>C/C</sup> allele was 1.33 years (0.84-1.75) (p<0.001); the survival of patients with <i>C9ORF72</i><sup>≥30</sup> and <i>UNC13A</i><sup>C/C</sup> allele was 1.66 years (1.41-2.16). Each pair of detrimental alleles/expansions was associated to specific clinical phenotypes. <h3>Conclusions.</h3> We showed that gene variants acting as modifiers of ALS survival or phenotype can act on their own or in unison. Overall, 54% of patients carried at least one detrimental common variant or repeat expansion, emphasizing the clinical impact of our findings. In addition, the identification of the interactive effects of modifier genes represents a crucial clue for explaining ALS clinical heterogeneity and should be considered when designing and interpreting clinical trials results.