Abstract
Purpose: :
Retinal Astrocytes play a pivotal role in the survival of retinal ganglion cells as well as retinal homeostasis. During development and disease, astrocytes exhibit changes in expression profiles as a result of chromatin reorganization. Chromatin reorganization can be induced through the modification of histones that form the core of proteins around which DNA is wrapped in the nucleus. The acetylation level of histones is governed by the opposing effects of two enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs), which are responsible for adding and removing acetyl groups from lysine residues, respectively. HATs and HDACs are known to regulate transcription by modifying the histones thereby enabling or restricting the access of transcription factors respectively. We examined the expression of HATs and HDACs in developing retinal astrocytes to understand their role in epigenetics of astrocytes during development and disease.
Methods: :
The expression of HATs and HDACs were ascertained in cultured murine retinal astrocytes and mouse cryosections from embryonic day 16 and postnatal day 30 through the developing optic nerve. Expression of HATs, namely p300 and P/CAF as well as class I HDACs namely HDAC 1,2,3 and 8 and class IV HDAC namely HDAC 11 were confirmed by western blotting as well as immunolabeling using specific antibodies. Astrocytes as well as tissue sections were double labeled for HAT/HDAC and tubulin followed by Hoechst stain to visualize the nucleus. The expression of HDACs following immunolabeling was examined by confocal fluorescence microscopy.
Results: :
Western blotting confirmed the expression of HATs and HDACs in retinal astrocytes. Immunolabeling of cultured astrocytes and developing astrocytes in vivo revealed that both the HATs and HDACs localize predominantly to the nucleus. Overall, expression of many of the HDACs appeared to be more abundant than HATs in the developing retinal astrocytes.
Conclusions: :
The expression of HATs as well as class I and class IV HDACs in retinal astrocytes suggests their involvement in the epigenetic regulation of developing astrocytes.
Keywords: astrocyte • retinal development • retina