One might expect that protein abundances in cytoplasm and mitochondria to be correlated with mRNA expression levels. However, we found that the functional modules of down-regulated proteins have up-regulated mRNA levels, suggesting that downregulated proteins might experience difficulties in protein import into r 0 mitochondria. To understand the differences of mRNA and protein expression of those proteins, we examined the levels of protein expression in r 0 cytoplasm and mitochondria by using western blot analyses. The tested proteins, GLUD1, GTPBP3, ATP5A1, TFAM, and NDUFS6, were selected from each downregulated functional module. We found that the cytoplasmic protein levels of GLUD1 (amino acid metabolism), GTPBP3 (tRNA metabolism), and ATP5A1 (ATP synthesis) were increased, whereas the mitochondrial levels of those proteins were found to be decreased ( Figure S3 ), suggesting that those proteins remained in the cytoplasm and did not properly transport into mitochondria. Meanwhile, both cytoplasmic and mitochondrial protein levels of TFAM (mtDNA replication) and NDUFS6 (electron transport) were decreased ( Figure S3) . It might be possible that these proteins degraded more rapidly than synthesized in r 0 cell, consequently showed down-regulated protein expression levels.