Retinal pathology and skin barrier defect in mice carrying aStargardt disease-3 mutation in elongase of very long chain fattyacids-4

[摘要] Purpose: Autosomal dominant Stargardt disease-3 (STGD3) is caused bymutations in elongase of very long chain fatty acids-4 (ELOVL4). Thegoal of this study was to generate and characterize heterozygous andhomozygous knockin-mice that carry a human STGD3 pathogenic mutation inthe mouse Elovl4 gene.Methods: Recombinant Stgd3-knockin mice were generated using a DNAconstruct which introduced a pathogenic five-base pair deletion and twopoint mutations in exon 6 of the Elovl4 gene. Stgd3-mouse genotypeswere confirmed by Southern blot analysis and expression of wild-type(wt) and mutated Elovl4 mRNAs assayed by nuclease protection assay. Theretinal phenotype of heterozygous Stgd3 mice was characterized bymorphological studies, elecroretinographic (ERG) analysis and assay oflipofuscin accumulation. Homozygous Stgd3 mice were examined for bothretinal and gross morphology. They were also analyzed for skinmorphology and skin barrier function, and for epidermal lipid contentusing high performance liquid chromatography (HPLC) combined with massspectrometry (MS).Results: The Stgd3 allele codes for a truncated mouse Elovl4protein, which also contains the same aberrant 8-amino acid C-terminusencoded by the human pathogenic STGD3 allele. Heterozygous Stgd3 miceexpressed equal amounts of both wt and mutant Elovl4 mRNAs in theretina, showed no significant changes in retinal morphology, but didshow accumulation of lipofuscin and reduced visual function. HomozygousStgd3 mice were born with an expected Mendelian frequency, without anyinitial gross anatomical or behavioral abnormalities. By 6-12 hpostpartum, they became dehydrated and died. A skin permeability assaydetected a defect in epidermal barrier function. Homozygous mutantepidermis expressed a normal content of mutated Elovl4 mRNA andcontained all four epidermal cellular layers. HPLC/MS analysis ofepidermal lipids revealed the presence of all barrier lipids with theexception of the complete absence of acylceramides, the critical lipidsfor barrier function of the skin.Conclusions: The generated Stgd3-knockin mice are a genetic model ofhuman STGD3 and reproduce features of the human disease: accumulation oflipofuscin and reduced visual functions. Homozygous Stgd3 mice showed acomplete absence of acylceramides from the epidermis. Their absencesuggests a role for Elovl4 in acylceramide synthesis, and in particular,a role in the synthesis of the unique very long chain C30-C40 fattyacids present in skin acylceramides.

[学科分类] 生物化学/生物物理