Human Molecular Genetics Advance Access originally published online on November 20, 2006
Human Molecular Genetics 2006 15(24):3569-3577; doi:10.1093/hmg/ddl433
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ENU mutagenesis identifies mice with cardiac fibrosis and hepatic steatosis caused by a mutation in the mitochondrial trifunctional protein ß-subunit
1 Institute of Biomedical Sciences, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 11529, Taiwan, 2 Graduate Institutes of Life Sciences, National Defense Medical Center, Taipei 11490, Taiwan, 3 Department of Medical Research, China Medical College Hospital, Taichung 40408, Taiwan and 4 Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA
* To whom correspondence should be addressed. Tel: +011 886227899104; Fax: +011 886227825573; Email: chen0010{at}ibms.sinica.edu.tw
Received October 2, 2006; Accepted November 8, 2006
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) 
- and ß-subunits, respectively, are located. Direct sequencing revealed a normal -subunit, but detected a nucleotide T-to-A transversion in exon 14 (c.1210T>A) of ß-subunit (Hadhb) which resulted in a missense mutation of methionine to lysine (M404K). Western blot analysis showed a significant reduction of both the - and ß-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.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.