Alternative splicing in Acad8 resulting a mitochondrial defect and progressive hepatic steatosis in mice.

Using a combination of N-ethyl-N-nitrosourea-mediated mutagenesis and metabolomics-guided screening, we identified mice with elevated blood levels of short-chain C4-acylcarnitine and increased urine isobutyryl-glycine. Genome-wide homozygosity screening, followed by fine mapping, located the disease gene to 15-25 Mb of mouse chromosome 9 where a candidate gene, Acad8, encoding mitochondrial isobutyryl-CoA dehydrogenase was located. Genomic DNA sequencing revealed a single-nucleotide mutation at -17 of the first intron of Acad8 in affected mice. cDNA sequencing revealed an intronic 28-bp insertion at the site of the mutation, which caused a frame shift with a premature stop codon. In vitro splicing assay confirmed that the mutation was sufficient to activate an upstream, aberrant 3' splice site. There was a reduction in the expression of Acad8 at both the mRNA and protein levels. The mutant mice grew normally but demonstrated cold intolerance at young age with a progressive hepatic steatosis. Homozygous mutant mice hepatocytes had abnormal mitochondria with crystalline inclusions, suggestive of mitochondriopathy. This mouse model of isobutyryl-CoA dehydrogenase deficiency could provide us a better understanding of the possible role of IBD deficiency in mitochondriopathy and fatty liver.

Mutations in the SLC2A10 gene cause arterial abnormalities in mice.

AIMS: Glucose transporter 10 (GLUT10), encoded by the SLC2A10 gene, is a member of the class III facilitative glucose transporter family. Mutations in the SLC2A10 gene cause arterial tortuosity syndrome (ATS) in humans. To further study the pathogenesis of the disease, we generated mice carrying GLUT10 mutations. METHODS AND RESULTS: Using a gene-driven N-ethyl-N-nitrosourea (ENU)-mutagenesis approach, we generated mice carrying GLUT10 mutations c.383G>A and c.449C>T, which resulted in missense mutations of glycine to glutamic acid (p.G128E) and serine to phenylalanine (p.S150F), respectively. Both mutant strains appeared normal at birth, gained weight appropriately and survived to adulthood (>18 months). Blood and urine glucose were normal. Echocardiogram and electrocardiogram were also normal and brain magnetic resonance angiography revealed normal cerebral arteries without tortuosity, stenosis/dilatation, or aneurysm. Histopathology revealed thickening and irregular vessel wall shape of large and medium size arteries characterized by markedly increased elastic fibres, both in number and size. There was also intima endothelial hypertrophy and deranged elastic fibres that resulted in disruption of internal elastic lamina in the aorta of older mice. CONCLUSION: Abnormal elastogenesis with early elastic fibre proliferation provides a clue to the pathogenesis of arterial tortuosity in human ATS. Availability of this mouse model will allow testing of the relationship between diabetes and its vascular complications, including diabetic retinopathy, nephropathy and peripheral vascular disease.