Abstract
Purpose :
The role of Brn3 transcription factors in development of cell-specific dendritic arbors and synapse formation in the inner retina is not clearly understood. Brn3s regulate several genes in the retina that might have an important role in synapse formation. From the RNA sequencing done previously in our lab on wild –type and Brn3b -/- mouse retinas and purified RGCs, we identified a family of proteins-Copines which are regulated by Brn3b. Copines are intracellular proteins containing two C2 domains and an integrin like von Willebrand A domain. In this work, we investigate the distribution pattern of different Copines in the retina.
Methods :
There are nine Copines (1 to 9) present in the mammalian genome. Based on RNAseq data we predicted that 5 of them are differentially expressed in RGCs. We studied their expression in the inner retina, specifically in the RGCs, using in-situ hybridization. Cell type specific expression pattern was studied using immunohistochemistry (IHC) with commercially available and in-house antibodies for different Copines. The sub-cellular distribution of some of these Copine family members was also studied using IHC in a Cre dependent expression in Brn3b RGCs after intraocular injection with AAV constructs for the Copines.
Results :
Five Copine proteins are differentially expressed in the retina starting from early postnatal ages and have a dynamic expression through the retinal development. The different copines have a differential expression pattern in the RGCs and amacrine cells. The sub-cellular localization for the Copines indicate their presence in cell bodies as well as the dendrites of the RGCs.
Conclusions :
Our results show the differential expression of several Copines in the inner retina and also their sub-cellular localization within the Brn3b positive RGCs. Owing to the differences in their expression pattern and sub-cellular localization, the different Copines might participate in a combinatorial, cell type specific fashion in dendrite development and synaptogenesis in the inner retina.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.