Gas6, a ligand for the receptor protein-tyrosine kinase Tyro-3, is widely expressed in the central nervous system

Gas6 (growth arrest specific gene-ti) is a Ligand for members of the Axl su bfamily of receptor protein-tyrosine kinases. One of these receptors, Tyro- 3, is widely expressed in the central nervous system. We have used biochemi cal and histological techniques, including in situ hybridization, to determ ine the expression patterns of Gas6 mRNA and protein during development. Ga s6 is widely expressed in the rat central nervous system (CNS)beginning at late embryonic stages and its levels remain high in the adult. Gas6 is dete cted as a single 85 kDa protein, which is encoded by a single 2.5 kb mRNA s pecies. At embryonic day 14 it is detected in the heart, blood vessels, tes tes, choroid plexus, and in the ventral spinal cord. In the adult, Gasb is expressed in the cerebral cortex, (predominantly in layer V), the piriform cortex, and the hippocampus (areas CA1, CA3 and the dentate gyrus). It is a lso expressed in thalamic and hypothalamic structures, the midbrain, and in a subset of motor and trigeminal nuclei. In the cerebellum, it is expresse d in Purkinje neurons and deep cerebellar nuclei. Protein S, a protein rela ted to Gas6, is only detected at low levels in the CNS. The spatial and tem poral profiles of Gas6 expression suggest that it could potentially serve a s the physiologically relevant ligand for Tyro-3 in the postnatal rat nervo us system. (C) 1999 Elsevier Science B.V. All rights reserved.