GDF9 and amyotrophic lateral sclerosis: In the brain, RESP18 expression was associated with a higher risk of ALS (OR 1.30; 95% CI 1.19–1.42), while GDF9, PTPRN, and GPX3 were associated with lower risks of ALS (GDF9: OR 0.77, 95% CI 0.67–0.88; PTRRN: OR 0.17, 95% CI 0.08–0.34; GPX3: OR 0.57, 95% CI 0.48–0.68) (Additional file 1: Table S5).