Appearance of PNA-binding cells within the outer nuclear layer coinciding with photoreceptor degeneration in rd mice

Peanut agglutinin (PNA), a lectin with affinity for galactose-galactosamine disaccharides, has been employed to monitor alterations in carbohydrate expression in retinal degenerative (rd) mice. Mice homozygous for the rd gene exhibit a rapid loss of rod photoreceptor cells in the first postnatal month; outer segment degeneration is first detected between postnatal days (P) 12-P14 and most rod photoreceptors degenerate by P30. In the rd mouse, PNA-binding cells are observed in the outer nuclear layer (ONL) between P10 and P18, a time corresponding to the intense phase of photoreceptor cell death (LaVail et al., 1982). At no time are PNA-positive cells identified within the ONL of control retinas. PNA-binding cells typically occur in groups and binding of the lectin appears to be restricted to granular elements of the cytoplasm. This report represents the first documentation of changes in the expression and/or accessibility of glycoconjugates in the degenerating ONL of the rd retina. Further analysis of the relationship between regional distribution of PNA-binding cells in the ONL and degenerating photoreceptors of the rd may lead to a better understanding of the mechanism of cell death induced by this mutation.