ENU mutagenesis identifies mice with cardiac fibrosis and hepatic steatosis caused by a mutation in the mitochondrial trifunctional protein beta-subunit.
Using the metabolomics-guided screening coupled to N-ethyl-N-nitrosourea-mediated mutagenesis, we identified mice that exhibited elevated levels of long-chain acylcarnitines. Whole genome homozygosity mapping with 262 SNP markers mapped the disease gene to chromosome 5 where candidate genes Hadha and Hadhb, encoding the mitochondria trifunctional protein (MTP) alpha- and beta-subunits, respectively, are located. Direct sequencing revealed a normal alpha-subunit, but detected a nucleotide T-to-A transversion in exon 14 (c.1210T>A) of beta-subunit (Hadhb) which resulted in a missense mutation of methionine to lysine (M404K). Western blot analysis showed a significant reduction of both the alpha- and beta-subunits, consistent with reduced enzyme activity in both the long-chain 3-hydroxyacyl-CoA dehydrogenase and the long-chain 3-ketoacyl-CoA thiolase activities. These mice had a decreased weight gain and cardiac arrhythmias which manifested from a prolonged PR interval to a complete atrio-ventricular dissociation, and died suddenly between 9 and 16 months of age. Histopathological studies showed multifocal cardiac fibrosis and hepatic steatosis. This mouse model will be useful to further investigate the mechanisms underlying arrhythmogenesis relating to lipotoxic cardiomyopathy and to investigate pathophysiology and treatment strategies for human MTP deficiency.
Kao
Hsiao-Jung
HJ
Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei, Taiwan.
Cheng
Ching-Feng
CF
Chen
Yen-Hui
YH
Hung
Shuen-Iu
SI
Huang
Cheng-Chih
CC
Millington
David
D
Kikuchi
Tateki
T
Wu
Jer-Yuarn
JY
Chen
Yuan-Tsong
YT
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002331:Carnitine / Q000031:analogs & derivatives / Q000378:metabolism; D002874:Chromosome Mapping; D005038:Ethylnitrosourea / Q000633:toxicity; D005234:Fatty Liver / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005355:Fibrosis; D052439:Lipid Metabolism Disorders / Q000139:chemically induced / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D063991:Mitochondrial Trifunctional Protein; D063992:Mitochondrial Trifunctional Protein, alpha Subunit; D063993:Mitochondrial Trifunctional Protein, beta Subunit; D009097:Multienzyme Complexes / Q000235:genetics* / Q000378:metabolism; D016296:Mutagenesis / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D053719:Tandem Mass Spectrometry
D009097:Multienzyme Complexes; C116917:acylcarnitine; C576205:HADHA protein, human; D063992:Mitochondrial Trifunctional Protein, alpha Subunit; C576206:HADHB protein, human; D063991:Mitochondrial Trifunctional Protein; D063993:Mitochondrial Trifunctional Protein, beta Subunit; D005038:Ethylnitrosourea; D002331:Carnitine