Figure 1.

Galectins and Siglec-4 contribute to the glia-mediated regulation of neuronal myelination. Oligodendrocytes are the cells responsible for myelination in the central nervous system (CNS). Under normal conditions, galectin-4 is delivered to the unmyelinated axonal regions and co-localizes with contactin-1 (a marker for nodes of Ranvier). The presence of galectin-4 inhibits oligodendrocytes from myelinating the region (Çolakoğlu et al., 2014). In addition, soluble galectin-4 inhibits the maturation of oligodendrocytes (Stancic et al., 2012). Siglec-4 is produced by oligodendrocytes and is expressed in the myelin sheath (Sun et al., 2004; Huang et al., 2012). Astrocytes and microglia promote the proliferation and differentiation, respectively, of oligodendrocytes. In particular, astrocytes secrete galectin-1 to drive microglia toward neuroprotective phenotype, while these microglia trigger the differentiation of oligodendrocytes in a galectin-3-dependent manner (Hoyos et al., 2014, 2016). Gal, galectin; Sig, Siglec.