PNKP and amyotrophic lateral sclerosis: Motor cortex in ALS also show significant CpG island demethylation compared to control at 2 of 5 sites in the Apex1 gene (Fig. 8b), 4 of 5 sites in the Pnkp gene (Fig. 8c) and 2 of 5 sites in the Aptx gene (Fig. 8d).