Abstract
Purpose :
In mice, it has been shown that loss of CIB2 (calcium and integrin binding protein 2) results in progressive retinal disease which recapitulates many characteristics of age-related macular degeneration (AMD). Cib2-KO mice demonstrate age-related vision impairments, accumulation of lipid deposits, and reduced lysosomal and autophagic capacity in the retinal pigment epithelium (RPE), due to dysregulation of mammalian target of rapamycin complex 1 (mTORC1). Here, unbiased transcriptomics in Cib2-KO mice were performed to assess molecular impacts of loss of CIB2, and to further decipher mechanisms through which CIB2 regulates cellular autophagy.
Methods :
RPE tissue samples, pooled from 2-3 mice for each biological replicate, were collected from Cib2-KO and wildtype (WT) mice at 2 (young) and 8 (aged) months of age. Bulk mRNA sequencing was performed from each sample using the Illumina HiSeq 4000. Reads were aligned to the UCSC mouse reference genome and quantified using HTSeq. Significant differentially expressed genes (DEGs) were assessed using DESeq, and unsupervised clustering of DEGs was performed using CLICK algorithm.
Results :
CLICK analysis revealed several functional pathways that were differentially expressed between sample groups. In both young and aged mice, pathways upregulated in Cib2-KO samples included Calcium Signaling, RhoA Signaling, and Integrin Signaling. Uniquely downregulated DEGs in young Cib2-KO animals were related to Complement and Coagulation Cascades, LXR/RXR Activation (related to lipid synthesis and transport), and Phagosomes. Aged Cib2-KO mice displayed the most significant downregulation of genes in the Phototransduction Pathway.
Conclusions :
Geographic atrophy in AMD is characterized by loss of photoreceptors and RPE, though a singular pathway has not been found responsible. Many current studies are investigating the role of complement activation, vesicle trafficking, and ion transport as top contributors to AMD development. We identified DEGs paralleling many of these molecular pathways in Cib2-KO mice, highlighting their potential use as a model to study age-related RPE pathologies and evaluate therapeutic interventions. Further study is needed to parse out individual genes and regulatory mechanisms involved, and extrapolate these findings to translational study of autophagy defects in the context of other disease and aging phenotypes.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.