Cellular Heterogeneity

Elizaveta Fasler-Kan, Nijas Aliu, Kerstin Wunderlich, Sylvia Ketterer, Sabrina Ruggiero, Steffen Berger, Peter Meyer

The retinal pigment epithelial cell line ARPE-19 was established in 1996 and remains widely used today for biomedical and in particular ophthalmology research. We have analyzed the chromosomes of the ARPE-19 cell line and found cultured cells exist as a heterogeneous mixture having both normal karyotypes and chromosomal rearrangements. In ARPE-19 cells, we observed metaphases with a single translocation t(15;19) and metaphases with two translocations t(5;15) and t(15;19) and a derivative chromosome 9. Aneuploidies have also been detected (monosomy: -16; trisomy: +11, +18). Multiple attempts to isolate clones with a normal karyotype from those with aberrant karyotypes failed due to senescence of cells of normal karyotypes. We could, however, isolate clones with the translocation t(15;19) and clones with two translocations t(5;15) and t(15;19). In continued cell culture after second subcloning for 30 passages, all clones maintained their cytogenetic integrity.We have further investigated the chromosomal profiles of the ARPE-19 cell line from another laboratory and observed cells with a normal karyotype as well as abnormalities in chromosomes 6p and 11q. The DNA profiles of the ARPE-19 cells from both labs were identical to the ATCC profiles, excluding contamination with other cell lines. Since chromosomal translocations in ARPE-19 cells differ from lab to lab and display a mosaicism for structural chromosomal aberrations, researchers dealing with ARPE-19 cells should screen their stocks for chromosomal aberrations and proceed with caution against misinterpretations during experimental manipulations with this cell line. This chapter describes in detail our laboratory methods for single cell cloning, karyotype analysis and fluorescence in situ hybridization (FISH), which we used for the identification and characterization of chromosomal translocations in the retinal pigment epithelial cell line ARPE-19.