Abstract
Purpose: :
Ocular Albinism type I (OA1) is an X-linked recessive disease due to mutations in the OA1 gene. This study is aimed at determining to which extent and how Oa1 gene function, confined in Retinal Pigment Epithelium (RPE) cells of the eye, impacts on visual system development.
Methods: :
Oa1 knock-out and wt littermates were analyzed during development (E15.5 - P0 - P30) in order to analyze structure and function of all centers that relay visual information (retina-thalamus-visual cortex) using immunological stainings (ISH, IHC), Electron Microscopy, two-color-eye-fill tracing, BrdU proliferation assays and Real Time PCR.
Results: :
At E15.5 we found a significant reduction of Retinal Ganglion Cells (RGCs) positive to EphB1, a marker of cells projecting ipsilaterally at chiasm. In addition, by Islet ½ staining we showed a significant reduction of contralaterally projecting RGCs. Consistent with these findings, in adulthood (P30) we observed a reduction of total number of RGCs at optic nerve level and a reduction of both ipsi and contra-lateral volumes in the Lateral Geniculate Nuclei (dLGN). Furthermore serotonin uptake staining demonstrated that the thalamo-cortical projections are also reduced in Oa1 mice. Conversely, despite a normal V1 arealization, the reduced thalamic input present in Oa1 animals results in an increased expression of RorB layer IV specific marker. In addition, an increased cell density of layer IV was demonstrated by BrdU+ labeling. Finally, an altered Arc mRNA expression demonstrated a structural and functional anomaly of visual circuitry.
Conclusions: :
Our study indicates that ablation of Oa1 gene influences RGCs genesis and this in turn impacts on visual thalamic radiation development and visual corticogenesis.
Keywords: optic nerve • visual cortex • visual development