Multicentric referral-based study of ALS-related genes in an Argentine ALS/FTD cohort: preliminary results
Creators: name: Gargiulo-Monachelli, Gisella
name: LeBlond, Claire
name: Bettini, Mariela
name: Figueredo, Maria Alejandra
name: Mele, Ignacio
name: Garau, Maria Laura
name: Rugiero, Marcelo
name: Deniselle, Maria Claudia Gonzalez
name: Dion, Patrick A.
name: Pagano, Miguel A.
name: Rouleau, Guy
Publisher: name: F1000Research
Year: 2016

description: <i>Background and Objetives: </i>Genetically, <i>C9ORF72</i> repeat expansions are the most common cause of ALS and FTD [1]. We previously found in an Argentine ALS and FTD cohort that C9+ cases involved patients with a positive family history of disease. C9+ ALS was associated with a young onset, rapid progression, initial bulbar symptoms and the co-existence of non-motor phenotypes (FTD and psychiatric disease) [2]. Our objective was to expand our previous work with high-throughput sequencing to screen for 28 ALS-related genes in a larger cohort of ALS and FTD patients in Argentina.<i><br><br>Methods:</i> To assess the mutation frequency of ALS-associated-genes in ALS cases we screened 28 genes (<i>SOD1, FUS, TARDBP, C9ORF72, VAPB, VCP, UBQLN2, DAO, PFN1, hnRNPA2B1, hnRNPA1, ANG, FIG4, OPTN, DCTN1, CHMP2B, NEFH, PRPH, SQSTM1, TAF15, HFE, GRN, ARHGEF28, ERBB4, SPAST, P4HB, PDIA2 and PDIA3</i>) in a cohort of 109 ALS/FTD patients. Single nucleotide variations were studied using Molecular Inverted Probe (MIP) captures and Illumina sequencing (PMID=23160955) for the 28 genes. Hexanucleotide repeats of <i>C9ORF72 </i>were studied by repeat-primed-PCR (PMID= 21944779 &amp; 21944778) in 60 patients from the cohort.<br><br><i>Results:</i> A total of 114 patients were recruited between August 2012 and Nov 2015 of whom 109 were ALS, FTD or ALS+FTD; and 5 were other MND. From the former cohort, 52.3% were males. Mean age of onset was 53 years old. Clinical characteristics ranged from: classic ALS (n=48, 44%), bulbar onset ALS or progressive bulbar palsy (n=9, 8.3%), UMN dominant-ALS (n=10, 9.2%), ALS+FTD (n=11, 10.1%), Flail arm or flail leg (n=8, 7.3%), PLS (n=4, 3.7%), PMA (n=7, 6.4%), FTD only (n=3, 2.8%), slowly progressive ALS, defined as &gt;10 years from symptom onset (n=5, 4.6%), ALS+Parkinson disease (n=2, 1.8%) and respiratory onset ALS (n=2, 1.8%). By a more stringent definition of FALS (one first or second degree relative with ALS), 15.6% of patients were FALS (n=14). By a more broad definition that includes ALS and/or FTD cases in one first or second degree relative, 21.1% of patients were FALS (FALSwFTD). Molecular Inverted Probe (MIP) captures and Illumina sequencing for the 28 ALS-related genes were done for the entire cohort, but only the FALS patients (n=14) were analyzed by a team of neurologists and computational biologists to assign pathogenic variants. From the RP-PCR analysis, 30% of FALS and 0% of SALS had the C9+ expansion. The high-throughput seq revealed mutations in <i>SOD1</i> (14%), <i>ERBB4</i> (14%), <i>FUS</i> (14%), <i>TAF15 </i>(14%) and others (<i>HFE, DCNT1, GRN</i> and <i>HNRNPA1</i>). It is noteworthy that only 15% was unknown and 7% had &gt;1 variant. Pending are the seq analyses from the SALS cohort. The <i>TBK1</i> and <i>NEK1 </i>genes were not included in the panel, and we did not look for repeats at the <i>ATXN</i> gene.<br><br><i>Conclusions: </i>Preliminary results suggest that the <i>C9ORF72</i> expansion represents a rare cause of sporadic ALS in Argentina, but probably the most common cause of ALS in FALS patients. With a 28 gene panel we could determine 85% of FALS cases, with a similar distribution among the following genes: <i>SOD1, ERBB4, TAF15</i> and <i>FUS</i>. We probably found a novel mutation at the <i>HFE</i> gene in a FALS pedigree (along with the <i>HFE</i> H63D polymorphism already described among SALS patients). We still have to finish analyzing the SALS cohort  for gene variants.<br><br><br>References:<br>[1] Majounie E, Renton AE, Mok K, et al. Lancet Neurol 2012; 11: 323–30.<br>[2] Gargiulo-Monachelli G, LeBlond CS, Bettini M, et al. In: Annual Meeting of the American Academy of Neurology. Neurology April 6, 2015; vol 84, Suppl 14; Abstract P02.050