Expressed sequence tag analysis of adult human iris for the NEIBank Project: steroid-response factors and similarities with retinal pigment epithelium.

Purpose: The iris is a specialized tissue with important roles in the development and function of the eye. It is involved in diseases, including glaucoma and ocular melanoma, and its pigmented cells share an origin with the retinal pigment epithelium (RPE). Expressed sequence tag (EST) analysis of human iris has been performed to explore the repertoire of genes expressed in this tissue.
Methods: An unamplified, un-normalized cDNA library (designated bx) was constructed from pooled (4-80 years old) human iris tissue. Over 2000 clones were picked and sequenced. Sequences were analyzed and clustered using GRIST (GRouping and Identification of Sequence Tags). The library was then normalized (and designated fg) and a further 2200 clones were sequenced for deeper examination of rarer sequence. Some sequences of interest were investigated further by standard methods.
Results: From bx and fg libraries respectively, 1263 and 1604 clusters of expressed genes have been identified, giving a combined total of almost 2700 potentially unique genes. The most abundant novel transcript in bx is oculoglycan/opticin. Others include glucocorticoid induced leucine zipper protein (GILZ), Ris, a novel member of the Ras family, Iris Ring Finger (IRF), a member of the midline family, melastatin 2 (MLSN2), a member of the transient receptor potential calcium channel family, and iris expressed growth factor (IEGF), a member of the VEGF/PDGF family. Several factors involved in steroid responses are also represented.
Conclusions: The iris libraries are a rich source of novel as well as known genes, including molecular markers for pigmented cells that are also shared with RPE. A number of transcripts code for proteins involved in steroid response, with interesting implications for control of intraocular pressure. These sequence verified clones provide a nonredundant set for micro-array construction.