Leber’ s hereditary optic neuropathy (LHON) is thought to be the most common disease resulting from mitochondrial DNA (mtDNA) point mutations, and transmito chondrial cytoplasmic hybrid (cybrid) cell lines are the most frequently used mo del for understanding the pathogenesis of mitochondrial disorders. We have used oligonucleotide microarrays and a novel study design based on shared transcripts to allocate transcriptomal changes into rho- zero- dependent, cybridization- dependent and LHON dependent categories in these cells. The analysis indicates that the rho- zero process has the largest transcriptomal impact, followed by t he cybridization process, and finally the LHON mutations. The transcriptomal imp acts of the rho- zero and cybridization processes preferentially and significan tly affect the mitochondrial compartment, causing upregulation of many transcrip ts involved in oxidative phosphorylation, presumably in response to the mtDNA de pletion that occurs at the rhozero step. Nine LHON- specific transcriptional al terations were shared among osteosarcoma cybrids and lymphoblasts bearing LHON m utations. Notably, the aldose reductase transcript was overexpressed in LHON cyb rids and lymphoblasts. Aldose reductase is also overexpressed in diabetic retino pathy, leading to optic nerve and retinal complications. The LHON- specific inc rease in transcript level was confirmed by quantitative reverse transcription- polymerase chain reaction (RT- PCR), and a western blot confirmed a higher leve l of aldose reductase in mutant mitochondria. One product of aldose reductase is sorbitol, which has been linked to osmotic stress, oxidative stress and optic n europathy, and sorbitol levels were increased in LHON cybrids. If these results are confirmed in patient tissues, aldose reductase inhibitors could have some th erapeutic value for LHON.  u001a Leber ’s hereditary optic neuropathy (LHON) is thought to be the most common disease resulting from mitochondrial DNA (mtDNA) point mutations, and transmito chondrial cytoplasmic hybrid (cybrid) cell lines are the most frequently used mo del for understanding the pathogenesis of mitochondrial We have used oligonucleotide microarrays and a novel study design based on shared transcripts to allocate transcriptomal changes into rho-zero-dependent, cybridization- dependent and LHON dependent categories in these cells. The analysis indicates that the rho-zero process has the largest transcriptomal impact, followed by t he cybridization process, and finally the LHON mutations. The transcriptomal imp acts of the rho-zero and cybridization processes preferentially and significantly affect the mitochondrial compartment, causing upregulation of many transcrip ts involved in oxidative phosphorylation, presumably in response to the mtDNA de pletion that occurs at the rhozero step. Nine LHON-specific transcriptional al terations were shared among osteosarcoma cybrids and lymphoblasts bearing LHON m utations. Notably, the aldose reductase transcript was overexpressed in LHON cyb rids and lymphoblasts. Aldose reductase is also overexpressed in diabetic retino pathy, leading to optic nerve and retinal complications. The LHON-specific inc rease in transcript level was confirmed by quantitative reverse transcription-polymerase chain reaction (RT-PCR), and a western blot confirmed a higher leve l of aldose reductase in mutant mitochondria. One product of aldose reductase is sorbitol , which has been linked to osmotic stress, oxidative stress and optic n europathy, and sorbitol levels were increased in LHON cybrids. If these results are confirmed in LHON cybrids.  u001a