Mitochondrial structure and function in the untreated Jackson toxic milk (tx-j) mouse, a model for Wilson disease.
Structural changes in hepatocellular mitochondria are characteristic of Wilson disease (WD). Features include variability in size and shape, increased density of matrix, discreet inclusions, and cystic dilatation of the cristae. We examined the functional basis for these mitochondrial changes in the toxic milk (tx-j) mouse model for WD. Its normal syngeic strain, C3H, served as control. Hepatic histology was near-normal in tx-j mice at 3-4-months-old and showed mild inflammation and steatosis at 6-months-old. Transmission electron microscopy showed typical mitochondrial abnormalities, specifically cystic dilatation of tips of cristae, in 3, 4, and 6-month-old tx-j mice and none in normal 3-month-old C3H mice. Citrate synthase (CS) activity was initially lower in tx-j mice than age-matched controls but increased over the first 6 months such that it was significantly greater at 5 and 6-months-old (p<0.003). No evidence for hepatic mtDNA depletion was found by long-PCR analysis. NB-PAGE showed preservation of all complexes in the oxidative-phosphorylation chain except complex IV which declined markedly from 5-months-old onwards. Hepatic complex IV activity was significantly decreased in 5-month-old tx-j mice (p<0.04). Expression of mitochondrial transfer factor A (TFAM) mRNA declined progressively in 6-8-month-old tx-j mice; immunodetectable protein levels declined in parallel. Expression of mtSSB mRNA was uniformly low in tx-j mice from 1-8-months-old. Levels of two mitochondrial antioxidant proteins capable of binding copper, thioredoxin-2 and peroxiredoxin-3, rose over the first 6 months of life. Mitochondrial changes occur early in WD and reflect complex, probably oxidative, injury.
Roberts
Eve A
EA
Genetics and Genomic Biology Program, Hospital for Sick Children Research Institute, University of Toronto, 555 University Avenue, Toronto, Ontario, Canada. eve.roberts@sickkids.ca
Robinson
Brian H
BH
Yang
Suyun
S
D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000032:analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D018450:Disease Progression; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism / Q000502:physiology; D005260:Female; D022781:Hepatocytes / Q000648:ultrastructure; D006527:Hepatolenticular Degeneration / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008817:Mice, Mutant Strains; D008892:Milk; D008930:Mitochondria, Liver / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure*; D010085:Oxidative Phosphorylation; D061105:Peroxiredoxin III; D054464:Peroxiredoxins / Q000235:genetics / Q000378:metabolism; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D045222:Electron Transport Chain Complex Proteins; D006609:High Mobility Group Proteins; C516116:Prdx3 protein, mouse; C081930:Tfam protein, mouse; C516112:Txn2 protein, mouse; C484072:mtSSB protein, mouse; D013879:Thioredoxins; D061105:Peroxiredoxin III; D054464:Peroxiredoxins; D002950:Citrate (si)-Synthase