Article

Haploinsufficiency is not the key mechanism of pathogenesis in a heterozygous Elovl4 knockout mouse model of STGD3 disease.

NIDCD/NEI, National Institutes of Health, Bethesda, MD 20892, USA.
Investigative Ophthalmology &amp Visual Science (impact factor: 3.6). 09/2006; 47(8):3603-11. DOI:10.1167/iovs.05-1527 pp.3603-11
Source: PubMed

ABSTRACT Autosomal dominant Stargardt-like (STGD3) disease results from mutations in the ELOVL4 gene (elongation of very-long-chain fatty acids). This study was undertaken to characterize a mouse model with a targeted deletion of Elovl4 and to explore the role of this gene in retinal/macular degeneration.
A construct targeted to exon 2 of the Elovl4 gene was used to suppress expression of the gene. Elovl4 homozygous pups were nonviable and were not available for study. Hence, the analysis was performed on heterozygous Elovl4(+/-) mice 16 to 22 month of age and littermate wild-type (WT) control mice of the same age. Characterization included examining gene message and protein levels, electroretinogram (ERG), retinal morphology and ultrastructure, and plasma and retinal fatty acid composition.
Although the level of Elovl4 mRNA was reduced in Elovl4(+/-) retinas, only minimal morphologic abnormalities were found, and the retinal (ERG) function was essentially normal in Elovl4(+/-) retinas compared with the WT control retinas. Systemic fatty acid profiles of Elovl4(+/-) mice were unremarkable, although the concentration of several fatty acids was significantly lower in Elovl4(+/-) retinas, particularly the monounsaturated fatty acids.
The detailed characterization of this animal model provides the first in vivo evidence that Elovl4 haploinsufficiency is not the underlying key disease mechanism in STGD3. The results are consistent with a dominant negative mechanism for the deletion mutation. The Elovl4 knockout mouse is one of three complementary animal models that will help elucidate the disease mechanism.

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Keywords

animal model
 
complementary animal models
 
Elovl4 gene
 
Elovl4 haploinsufficiency
 
Elovl4 homozygous pups
 
Elovl4 knockout mouse
 
Elovl4 mRNA
 
fatty acids
 
gene message
 
heterozygous Elovl4(+/-)
 
minimal morphologic abnormalities
 
monounsaturated fatty acids
 
mouse model
 
protein levels
 
retinal fatty acid composition
 
retinal morphology
 
Systemic fatty acid profiles
 
targeted deletion
 
very-long-chain fatty acids
 
WT control retinas