COMPLEX EXPRESSION OF KERATINS IN GOLDFISH OPTIC-NERVE

Keratins are the predominant intermediate filament proteins in the non neuronal cells of the goldfish optic nerve. At least three different k eratin pairs are expressed in this tissue, indicating an unexpected co mplexity. Expression of the type II keratin ON3 in goldfish optic nerv e astrocytes predicts the expression of a type I keratin partner. Here we report the cDNA sequence and predicted amino acid sequence of two type I keratins from the goldfish optic nerve, designated GK48 and GK4 9. The GK48 protein is the goldfish equivalent of mammalian keratin 18 (K18) and is the most likely type I keratin partner to the ON3 protei n. The GK49 protein is similar to the GK50 protein, a type I keratin c haracterized previously from the goldfish optic nerve. The GK48 and ON 3 mRNAs are expressed in a variety of goldfish tissues, whereas the ex pression of GK49 mRNA has a more limited expression. In addition, in s itu hybridization experiments show that the expression of the GK48 and ON3 mRNAs are evenly distributed throughout the optic nerve, while th e GK49 mRNA is expressed along longitudinal lines. These results show that there is a diversity of keratin expression within different cell types in the goldfish optic nerve. (C) 1994 Wiley-Liss, Inc.