ISOLATION AND CHARACTERIZATION OF CELL-SPECIFIC CDNA CLONES FROM A SUBTRACTIVE LIBRARY OF THE OCULAR CILIARY BODY OF A SINGLE NORMAL HUMAN DONOR - TRANSCRIPTION AND SYNTHESIS OF PLASMA-PROTEINS

A subtractive cDNA library was developed for the purpose of identifyin g cell-specific genes expressed within the human ocular ciliary body, a tissue responsible for regulating aqueous humor secretion and intrao cular pressure, Partial DNA sequence of a large number of cDNA clones and homology searches of nucleic acid and protein databases revealed s ignificant homologies to at least 90 independently known genes, A grou p of biologically significant genes that were previously not known to have transcriptional expression in the ciliary body, complement compon ent C4; alpha 2 macroglobulin; selenoprotein-P; and apolipoprotein D, were further demonstrated by Northern hybridization, Antibodies to the se and other proteins (i.e., tyrosinase-related protein and pigment ep ithelium-derived factor) cofirmed their cell-restricted expression in ciliary epithelial cells (pigmented, nonpigmented), or vascular endoth elial cells, We provide evidence that two human plasma proteins, compl ement component C4 and alpha 2-macroglobulin are metabolically labeled with [S-35]methionine in ciliary processes explants, suggesting that the ciliary body is an organ of synthesis and secretion of plasma prot eins present in aqueous humor, These results challenge the notion that plasma proteins in aqueous humor are imported from outside of the eye , The subtractive cDNA library reported in this work should be very us eful for identifying potential candidate genes in ocular abnormalities affecting the ciliary body, or involved in the regulation of intraocu lar pressure.