Abstract
Purpose:
Extracellular matrix proteins (ECMPs) play a critical role in the three-dimensional (3D) construction of distinct interconnected cell layers in the developing retina. ECMPs participate in remodeling and damage repair during aging and disease conditions. Cell replacement therapies that include transplantation of photoreceptors (PRs) in degenerating retina would also greatly benefit from the better understanding of ECMPs that are associated with early lamination in developing retina.
Methods:
We carried out the high-throughput transcriptome profiling of developing and mature mouse retina using RNA-seq, Affymetrix exon arrays and quantitative reverse transcription polymerase chain reaction (qRT-PCR) methods. Of approximately 16,000 expressed genes from developmental RNA-seq data, we focused on the analysis of about 50 genes that encode the ECMPs, such as Vitronectin: Vtn, Collagen subtypes: Col, Fibronectin: Fn, Proteoglycans and Integrin subtypes. We also examined the expression of ECMP genes in RNA-seq data from purified rod photoreceptors. Immunohistochemistry was performed for selected ECMPs using mouse, primate and human retina sections.
Results:
We analyzed a subset of mouse retinal transcriptome (MRT) for cytoskeletal proteins, tubulins, actins and their cross-linking factors, microtubulin-actin crosslinking factor, MACF, cell adhesion molecules and ECMPs that are all threaded in a spatially self-organized 3D cell cluster and are very dynamic in orchestrating the 3D structure from birth, development and degeneration till death of an organism. Transcription dynamics was evaluated by plotting the normalized expression value of transcription with the age of developing mice. With some exceptions, the transcription levels reached a plateau in 30 days, suggesting a possible homeostasis of the corresponding proteins (ECM-proteostasis). The mean transcript ratios of ECMPs to Integrins are about 9 and 6 for mice and human respectively.
Conclusions:
RNA expression data for ECMPs and photoreceptor integrins are concordant with immunohistochemistry of retina. Our studies for the first time, uncover the developmental expression profile of ECMPs that are critical for retinal lamination and architecture. Identification of rod photoreceptor ECMPs can provide new avenues for exploring better strategies for integration of transplanted cells in the degenerating retinal milieu.
Keywords: 519 extracellular matrix •
698 retinal development •
533 gene/expression