Abstract
Purpose :
Familial exudative vitreoretinopathy (FEVR) is a genetic disorder in which the retinal vasculature fails to form fully (hypovascular). We discovered that loss of the T-box transcription factor, Tbx3, in mouse embryonic retinal progenitor cells results in a hypovascular retina. This study aimed to characterize this phenotype and determine how the loss of Tbx3 affects angiogenesis.
Methods :
To remove Tbx3, we crossed the validated Tbx3-floxed mice with the optic cup-Cre recombinase driver, BAC-Dkk3-CRE, and confirmed loss of retinal protein by western blot. Cryostat retinal sections and flat mounts were immunostained, imaged, and cells counted using standard techniques. Statistical analysis was performed using Prism v9.3. ImageJ (v1.52q) and Volocity (v6.3) software were used for analysis.
Results :
Blood vessels failed to extend to the edge of the P9 Tbx3 conditional knockout (cKO) retina and occupied significantly less of the total retinal surface area than wildtype siblings (WT, 0.489 ± 0.019; cKO, 0.230 ± 0.023). We also observed that the hyaloid artery failed to regress. At P30, we observed fewer branch points, decreased vascular density, and incomplete formation of the superficial plexus in mutant mice compared to controls. The astrocytic lattice was similarly stunted in the mutants, primarily in the dorsal region. Previous studies have shown that melanopsin-positive intrinsically photosensitive retinal ganglion (ipRGCs) and dopaminergic amacrine cells control retinal angiogenesis. At one month of age, we found a significant loss of ipRGCs (~30%) throughout the retina, with an even more substantial loss (~50%) in the dorsal region. In addition, we failed to detect the expression of tyrosine hydroxylase-positive amacrine cells in the Tbx3 cKO retina (3 litters: n=6 WT; n=5 cKO).
Conclusions :
The loss of Tbx3 in retinal progenitors inhibits retinal angiogenesis in a pattern consistent with previous mouse models of FEVR. Our working hypothesis is that defects in angiogenesis are caused by a loss of ipRGCs and the absence of dopaminergic amacrine cells. Future studies will determine the molecular mechanism driving this defect in the Tbx3 cKO retina.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.