Authors' contributions
EF participated in establishment and characterization of cell lines and performed ATP determinations. PW participated in mitochondrial analysis and immunocytochemistry. JE, TL-N, AMT, and HG participated in genotypic and additional phenotypic analysis of cell lines. DR and EC generated virus-conditioned medium for conditional immortalization of cells. MEM co-conceived of the study and assisted on drafting of the manuscript. SLC co-conceived of the study, participated in establishment and phenotypic analysis of cell lines, and drafted the manuscript. All authors read and approved the final manuscript.