Abstract Body: Background: We previously demonstrated retinal astrocyte expression of the transcription factor T-box 3 (Tbx3), and that its deletion at the optic cup stage disrupts neurogenesis, astrocyte migration, and angiogenesis in the dorsal retina. Here, we hypothesized that Tbx3-dependent mechanisms coordinate astrocyte migration independently of retinal ganglion cell–mediated signaling.
Methods: Astrocyte-specific Tbx3 knockout was achieved using Pdgfra-CreER^T2;Tbx3^Fl/Fl mice, with recombination induced via tamoxifen at E17.5 or P0 and validated through Ai9 reporter expression. Retinas were harvested at the indicated timepoints and stained using standard techniques. Astrocyte lattice formation and vascular growth were determined on ImageJ, while the vascular properties at P9 were evaluated on AngioTool.
Results: Tbx3 deletion at P0 delayed astrocyte migration by P3 (WT 1.00±0.026 n=3; cKO 0.666±0.038 n=4, P=0.000095) and this delay persisted at P5 (WT 1.00±0.034 n=4; cKO 0.826±0.031 n=4, P=0.000279). By P9, however, WT and cKO astrocytes reached the retinal periphery comparably (n = 4). Deletion at E17.5 produced a more pronounced migration delay at P5 than deletion at P0 (Δ lattice growth WT x cKO – E17.5: 38% P<0001 n=5 WT n=2 cKO; P0: 17.4% P<0.005 n=4). Despite delayed astrocyte migration, angiogenesis progressed similarly in WT and cKO retinas, with no changes observed in vascular growth (P3 WT 1.00±0.13 n=3; cKO 1.17±0.017 n=4; P5 WT 1.00±0.08 n=4; cKO 0.95±0.12 n=4) or completion of the superficial vascular plexus by P9.
Conclusions: Our findings reveal a novel Tbx3-dependent mechanism regulating astrocyte migration. Tbx3 loss delays early retinal migration in vivo, supporting a cell-autonomous role in astrocyte motility. Ongoing studies aim to define the molecular pathways through which Tbx3 orchestrates astrocyte migration, advancing our understanding of intrinsic mechanisms that support vascular development in the retina.