Evolutionary conservation of brain Thy-1 glycoprotein in vertebrates and invertebrates.

The evolutionary conservation of brain Thy-1 glycoprotein in 24 vertebrate and invertebrate species has been investigated by means of a soluble phase radioimmunoassay (RIA) and by the "Western blot" technique. The brain glycoproteins from virtually all the vertebrate species inhibited the precipitation of mouse Thy-1.1 by a rabbit anti-rat Thy-1 antiserum. Most reagents also inhibited the binding of a mouse anti-rat Thy-1 monoclonal antibody to rat Thy-1. Whole tissue glycoproteins from earthworm, snail and oyster and ganglia glycoproteins of a locust species were also found to be inhibitory. Western blotting analysis on NaDod SO4 polyacrylamide gel electrophoresis under reducing conditions revealed a Thy-1 homologous molecule (22-25 KD) in mammals, birds, fish, reptiles and invertebrate species. The snail Thy-1-like molecule was eluted from the gel and was shown to specifically inhibit the serological reaction. The rabbit anti-rat Thy-1 antiserum also detected a doublet molecule of approximately 85,000 KD, which is conserved in all species, including yeast and bacteria. The origin and nature of the presumed glycoproteins is unknown. Our results suggest that the Thy-1 molecule has been conserved throughout metazoan evolution and that the Thy-1 gene is the most conserved among the immune related genes (immunoglobulins, beta 2-microglobulin and major histocompatibility) which share extensive amino acid homology.