Cloning and characterization of a mammalian homolog of the Drosophila ring canal protein kelch

Purpose. To clone and characterize the mammalian homolog of the Drosophila ring canal protein kelch (mRCP) and determine its role in the development of the RPE and in RPE/retina interaction, kelch is involved in regulating cytoplasmic transport between nurse cells and the oocyte during oogenesis. The existence of a RCP homolog was first suggested by sequencing of clones from a subtracted library enriched for cDNAs expressed preferentially in the RPE and retina. Methods. Subtractive hybridization and random sequencing were used to isolate the clone from a bovine eye cup cDNA library. The subtractive library was generated as described (Chang, et.al., ARVO 1996). RT-PCR, library screening, in situ hybridization and DNA sequencing are being performed by standard methods. Results. The 237bp mRCP clone shows 57% homology to ORF2 of the 5.6kb Drosophila kelch gene. The blastx probability score (4. le-21) is highly significant. In addition, the mRCP shows homology to ESTs cloned from human retina, liver and fetal brain. Efforts are currently underway to obtain a full length cDNA and to determine the spatial and developmental expression pattern of mRCP. Conclusions The results suggest that a mRCP homolog exists and that it is expressed in the retina and/or RPE. Based on the function of kelch in Drosophila, mRCP may be involved in retina/RPE interaction during development.