Abstract
Purpose :
The mammalian retina does not regenerate, while retinas of cold-blooded animals generally have great regenerative capacity. The chick retina falls in between, generating Muller glia-derived progenitor cells (MGPCs) with limited neurogenic capacity. We investigated molecular mechanisms underlying MGPC production in the chick retina involving the role of histone acetylation. The state of histone acetylation is controlled by the activities of histone deacetylases (HDACs) and histone/lysine acetyl transferases (HAT/KATs).
Methods :
Retinal damage was induced in chicks by intraocular injection of NMDA. Bioinformatic expression analyses were performed using previously sequenced single cell RNA seq libraries of control or damaged retinas (Seurat package). HDAC activity was inhibited by injection of trichostatin A (TSA) into one eye; the other eye (injected with vehicle) served as a control. HAT/KAT activity was similarly inhibited using MG149 or curcumin. Eyes were isolated after 72 hours, hemisected, fixed, and processed for immunohistochemistry. MGPCs were identified by labelling for SOX2 and incorporated EdU and counted. Statistical comparisons were performed using Student’s t-test.
Results :
HDACs and HAT/KATs exhibited dynamic patterns of expression in Muller glia (MG) from control and damaged retinas. Inhibition of HDACs resulted in decreased MGPC production [control: 41.50 ± 36.23 MGPCs per retinal section, treated: 9.40 ± 10.96 MGPCs per section, p < 0.008 (n = 10)]. Conversely, inhibition of HAT/KATs using MG149 resulted in a significant increase in MGPCs [control: 5.0 ± 3.8 MGPCs per retinal section, treated: 37.0 ± 11.7 MGPCs per section, p < 0.002 (n = 4)]. Similarly, inhibition of HAT/KATs using curcumin increased the number of MGPCs in the damaged retina [control: 23.9 ± 17.2 MGPCs per retinal section, treated: 49.0 ± 24.6 MGPCs per section, p < 0.016 (n = 7)].
Conclusions :
We conclude that HDAC activity is normally required for reprogramming of Müller glia into MGPCs while HAT/KAT activity generally suppresses formation of proliferating MGPC. Additionally, treatment of damaged retinas with the HAT/KAT inhibitor MG149 results in a increase in neurogenesis. These results suggest that histone acetylation levels normally influence chromatin access to gene networks associated with maintenance of glial phenotype, reprogramming to progenitor-like cells.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.