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Yuri V. Sergeev, Lauren Dalvin, Jamie Temple, Monika B. Dolinska, Brian P. Brooks, Kerry Goetz; Molecular Modeling And Functional Analysis Of Pathogenic Mutations In the Nucleotide Binding Domains Of the Abca4 Transporter. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2390.
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Stargardt disease, the most common form of juvenile macular dystrophy, is largely caused by mutations in the ABCA4 gene and is associated with accumulation of lipofuscin in the retinal pigment epithelium and photoreceptor cell death. Approximately 30% of pathogenic missense mutations in the ABCA4 gene associated with Stargrardt disease and cone-rod dystrophy are in one or the other of the two nucleotide binding domains (NBD) of ABCA4. Here we report molecular modeling of these NBD’s and consider structural perturbations caused by mutations found in human Stargardt disease subjects.
The two NBD protein structures were modeled by homology to the known crystal structures of NBDs. Structures of NBD’s were refined and equilibrated using molecular dynamics. We then evaluated possible correlations of this modeling with retinal function studied in patients reported to eyeGENE® or found in the literature. Missense mutations in the NBD domains were modeled, and severity of each mutation was evaluated using a method1 combining protein stabilization energy and a Grantham distance. Finally, a computed impact score for each mutation was compared with values estimating phenotypic severity of disease (age of retinal disease onset).
Analysis of two groups of missense changes based on the severe and non-severe computed impact scores (cut-off ~0.4) resulted in a statistically significant difference in average ages of retinal disease initiation of the two groups (p-value<0.002). Thus, early onset of disease is associated with more severe mutations as predicted by our model and less severe NBD’s structure perturbations are expected for individuals with later appearance of the disease.
These findings suggest an apparent association between age of retinal disease onset and molecular severity of missense changes in the nucleotide binding domains in ABCA4.1Sergeev Y.V. et al. (2010). Human Molecular Genetics, 19, 7: 1302-1313.
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