Abstract
Purpose :
BMI1, also known as B lymphoma Mo-MLV insertion region 1, is a protein in the Polycomb group that is implicated in various cellular processes, including stem cell self-renewal and proliferation. Data suggests BMI1 plays a role in the regulation of retinal progenitor cell differentiation. However, the presence, location, and quantification of BMI1 in the adult human eye has never previously been reported.
Methods :
Fresh frozen and paraffin-embedded sections of normal donor human eyes (donor ages 20-90 years) were obtained from NDRI and Lions Eye Bank (n=37). Ocular tissues were dissected. The retina and RPE were carefully removed, and punch biopsies were performed to isolate the macula and peripheral retina. BMI1 location was examined by light and fluorescence microscopy. ELISA was used to quantify protein levels in ocular tissues. Statistical analyses were performed in GraphPad prism and one-way ANOVA test was used to assess significance.
Results :
The BMI1 protein was found in all ocular tissues at the following levels: cornea (335.2±203.2pg/ml), iris/ciliary body (389.0±157.9pg/ml), lens (1846.7±1795.4pg/ml), vitreous (530.3±424.2pg/ml), retina (1483.6±542.2pg/ml), and RPE (296.4±220.8pg/ml). BMI1 expression was noted ubiquitously in GCL (Ganglion cell layer), INL (Inner nuclear layer), ONL (Outer nuclear layer), and RPE (Retinal pigment epithelium) by immunofluorescence (Figure 1) with higher levels in the inner than outer retinal layers and the RPE. No significant differences were seen in the macular BMI1 levels in the RPE and retina compared to the peripheral retina. BMI1 is localized in the membrane, cytoplasm, and nucleus of RPE cells by confocal microscopy (Figure 2).
Conclusions :
These data demonstrate that BMI1 is expressed in all ocular tissues and fluids with the highest levels being found in the lens and retina. Further studies will illuminate the role BMI1 plays in adult ocular cells.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.