Expression of the Retinal Pigmented Epithelial Cell‐Specific pP344 Gene during Development of the Chicken Eye and Identification of Its Product

Abstract

In order to understand the transdifferentiation of the retinal pigmented epithelial cells (PECs) into the lens cells at the level of gene expression, a gene, tentatively called pP344 gene, was studied, because its expression appeared to be closely related with the differentiated state of PECs. We analyzed pP344 gene expression during chicken eye development by RT-PCR and in situ hybridization and also characterized the pP344 protein using antipeptide antibodies. In addition to the previous observation that the transcript of pP344 gene is limited to the pigmented epithelium and not detected in the melanocytes, we show here that the transcript is limited to retinal PECs and is never observed in iris or ciliary PECs. The time course of expression level showed two peaks; the first peak occurred around the 10th day similarly to the expression of melanosome-related genes, while the second peak occurred just after hatching when PECs had completely differentiated, suggesting that pP344 gene may be related to the function of fully differentiated PECs. Antisynthetic peptide antibodies detected pP344 protein in the culture medium of the PECs but not within the cells. Thus, we concluded that pP344 gene is specifically expressed by the retinal PEC and its product is a secreted protein.