Expression and functions of galectin-1 in sensory and motoneurons

Galectin-1 (Ga11) was the first identified member of the galectin family of beta-galactosidase-binding proteins. Ga11 has important roles in processes fundamental to growth and survival of an organism, including cell adhesion, cell proliferation and apoptosis, and is expressed in many tissues, including the nervous system. In the 1980s, research focused on the developmental regulation of Ga11 expression during neurogenesis. Ga11 was found to be expressed mainly in peripherally-projecting neurons beginning early in neurogenesis, and its expression is maintained at high levels in subpopulations of these neurons in the adult rodent. Although the expression pattern of Gall implied that it may be involved in axonal guidance or targeting of subsets of sensory and motoneurons, possible roles of Ga11 in the nervous system had not been confirmed until recently. Ga11 has since been shown to be required for the proper guidance of subsets of primary olfactory axons (to targets in the olfactory bulb) and of primary somatosensory axons (to targets in the superficial dorsal horn). In addition, Ga11 has been implicated in the regenerative response of axons following peripheral nerve injury. Ga11 has been shown to promote axonal regeneration through the activation of macrophages. Also, Ga11 may act within the injured neuron to enhance regrowth: the injury-induced regulation of Ga11in numerous types of peripherally- and centrally-projecting neurons correlates positively with the regenerative potential of their axons. In this review, we discuss the expression pattern of Ga11 in sensory and motoneurons, and the potential roles of Ga11 in development, axonal regeneration and neuropathic pain.