CXCL12 and amyotrophic lateral sclerosis: The ALS-dependent differential methylation of three genes encoding the chemokines CKLF-like MARVEL transmembrane domain-containing proteins 2 and 3 (CMTM2 and CMTM3) and the chemokine (C-X-C motif) ligand 12 (CXCL12), as well as the two transcription factors, STAT5A and the CCAAT/enhancer binding protein beta (C/EBPB) was assessed by pyrosequencing (Fig. S1).