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Thor Eysteinsson, Stefán Broddi Daníelsson, Andrea García Llorca, Hallur Reynisson, Margrét Helga Ogmundsdottir, Eiríkur Steingrímsson; Mutations in the microphthalmia transcription factor (Mitf) gene affect retinal vessel diameter. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5854.
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© ARVO (1962-2015); The Authors (2016-present)
We have found that mice with mutations in the microphthalmia transcription factor (Mitf) gene show various structural and functional changes in the retina and pigment epithelium, and apparently in the retinal vasculature. The purpose of this study is to determine the retinal vessel diameter in normal and Mitf mutant mice, to assess the vascular changes in Mitf mutant mice.
The following mutations were examined: Mitfmi-vga9/+, Mitfmi-enu22 /Mitfmi-enu22 and wild type, six animals in each group, 3 months old. Mice were anaesthetized by an intraperitoneal injection of 40 mg/kg Ketamine and 4 mg/kg Xylazine. A Micron IV rodent imaging system (Phoenix Research Labs) was used to obtain fundus images after intraperitoneal injection of fluorescein sodium salt (0.1%, 10 µl/kg). These images were processed with Adobe Photoshop and a custom written MATLAB program to extract the mean vascular diameter at a specific distance from the optic disc. Each of the mutant mice was compared to wild type mice. A separate comparison was done for retinal arteries, venules and both combined. The comparison was made with respect to the number of retinal vessels, mean diameter and mean total diameter (mean diameter x number of vessels).
When comparing Mitfmi-enu22 /Mitfmi-enu22 to wild type mice, we found a significant 25% increase in mean total retinal arterial diameter (P=0.012), a 19% increase in mean venular diameter (P=0.013) and a 31% increase in mean total retinal vessel diameter (P=0.004). When comparing Mitfmi-vga9/+ to the wild type mice, we found an 18% increase in mean total retinal venular diameter (P=0.015) and a 15% increase in mean total retinal vessel diameter (P=0.047), but no significant change in mean total retinal arterial diameter (P=0.118).
We have developed a method to measure retinal vessel diameter in fundus images from mice. We found an increase in retinal vasculature in Mitfmi-enu22 /Mitfmi-enu22 mice compared to wild type mice, suggesting that there is an increased demand for blood flow to the retina in these mice. The increase in retinal venular vasculature in Mitfmi-vga9/+ mice, without a corresponding increase in retinal arterial vasculature is a surprising finding which requires further study.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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