Hyaluronate receptor CD44 is expressed by astrocytes in the adult chicken and in astrocyte cell precursors in early development of the chick spinal cord

The role of the hyaluronate receptor, CD44, is well known in adult mammal a strocytes where it modulates neuron-glia interactions. However, no data exi st regarding its expression in other vertebrates during their development. In order to detect the expression of CD44 in the chicken and its possible i nvolvement in glial precursor migratory patterns during spinal cord develop ment, a monoclonal antibody (MoAb) against the mammalian standard isoform, CD44-H, was used in immunohistochemical and immunoblot assays. With these m ethods, CD44 hyaluronate receptors were found on mature astrocyte membranes of adult chicken spinal cord. Astrocytes were identified using a MoAb agai nst GFAP. During development, small clusters of CD44 labelled cells were se en lining the central canal starting from embryonic stage E10. These labell ed cells were dispersed in the dorsal, lateral and ventral funiculi of the spinal cord in the subsequent stages. After stage E15, the CD44 labelled ce lls were identified as astrocytes because of their GFAP immunoreactivity. W e conclude that CD44 receptors on immature astrocyte precursors should be c onsidered as early astrocyte markers which have a possible role during cell migratory dispersal.