and accounts for 4% of fals and 1% of sals. fus was identified in 2009 and is seen in 4% of fals and 1% of sals. vcp was identified in 2010 and accounts for 1% of fals and 1% of sals; atxn2, optn, and ubqln2 were associated with als that same year. another major milestone was the discovery of c9orf72 in 2011, which is the most common gene associated with als, accounting for about 40% of fals cases and 7% of sals cases. c9orf72 was also found to contribute significantly to frontotemporal dementia (ftd). sqstm1 was also identified in 2011, but accounts for 1% of fals and less than 1% of sals. pfn1 was identified in 2012, hnrnpa1 and hnrnpa2b1 in 2013, chchd10, matr3, and tuba4a in 2014, and tbk1 in 2015. c21orf2, ccnf, and nek1 were associated with als in 2016. the first genome-wide association study (gwas) of als was published in 2007, and 14 gwass total had been published through 2013. they have contributed significantly to our understanding of als genetics; for example, a 2010 gwas studying als in finland led to discovery of the role of mutations at the c9orf72 locus in als. however, a gene identified by a single gwas may not actually be associated with als, especially if the cohort size is small. in outbred populations, thousands of cases (people with als) and controls (people without als) are required for a gwas to have sufficient statistical power to confidently identify a gene's association with als.