Retina transcriptomic landscape of HbSS Townes - a sickle cell disease mouse model

Abstract

Purpose : Retinal alterations are the most important ocular manifestations of sickle cell disease. Proliferative sickle cell retinopathy (PSCR) is the most severe form of retinopathy, leading to retinal detachment and visual loss in 10 to 20% of the affected eyes. Here, we performed RNA-sequencing from the retina of the HbSS-Townes mouse model to gain insights into the molecular mechanisms underlying PSCR.

Methods : Eight-month-old female mice HbAA (C57BL/6J) and HbSS (Townes) were used (N=10/group). A) Characterization: The functional activity of the retina was evaluated using the UTAS-E3000 electroretinogram (ERG) system; Hematological, body weight, and spleen parameters were measured; Morphological parameters were analyzed by hematoxylin and eosin (HE) staining. The ocular globes were collected, and the retina was isolated. B) Transcriptome: RNA retina samples from HbSS and HbAA groups were sequenced using NovaSeq6000 (Illumina); Normalization, heatmap, principal component analysis (PCA), and differential gene expression (DEGs) analysis were performed through the edgeR package in R.

Results : We observed the following differences between the HbSS vs. HbAA groups: A) ERG showed a significant difference in A and B-waves amplitude followed by an increase in implicit time responses, indicating altered retinal activity in these mice; All hematological parameters were significantly different, as well as splenomegaly, indicating anemia and hemolysis. HE staining demonstrated increased vessels at the ganglion cell layer; B) PCA and heatmap confirmed the transcriptome profile difference between HbSS and HbAA (Figure 1). We identified 260 DEGs (139 upregulated/121 downregulated) in comparing HbSS vs HbAA. Among the DEGs, 31% are protein-coding genes (PCG). We identified a significant portion of noncoding genes, including 36% of pseudogenes, and 33% comprised lncRNA, snRNA, and miRNA. Pseudogenes are implicated in various cellular processes and pathological conditions and may compete with PCG for stabilizing factors and miRNAs, potentially influencing mRNA and protein expression levels.

Conclusions : Our studies demonstrated a distinct transcriptome profile in the retina of HbSS-Townes mice with retinal ischemia, highlighting the molecular complexity of PSCR. While the functional mechanisms of pseudogenes remain unclear, our findings offer avenues for future exploration of functional and molecular aspects of PSCR.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.