Changes in Gene Expression Profiling and Phenotype in Aged Multidrug Resistance Protein 4-Deficient Mouse Retina

Abstract

Purpose : Multidrug resistance protein 4 (MRP4) is an energy-dependent membrane transporter responsible for cellular efflux of a broad range of xenobiotics and physiological substrates. Here, we aimed to investigate the coeffects of ageing and MRP4 deficiency using gene expression microarray and morphological and electrophysiological analyses of the mouse retina.

Methods : Mrp4-knockout (null) mice and wild-type (WT) mice were reared in the same condition to 8-12 weeks (young) or 45-55 weeks (aged). RNA was extracted from 6 retinas for each mouse genotype (WT and Mrp4-null), and RNA microarray using Agilent SurePrint G3 Mouse Gene Expression Arrays 8x60K Ver. 2.0 and the following KEGG pathway analyses were performed. Then, retinal wholemount immunostaining, immunohistochemical and H&E staining of tissue sections were conducted to assess changes in retinal layers and retinal cell types among 4 age/genotype categories (young/aged WT mice and young/aged Mrp4-null mice). Finally, electroretinogram was recorded to detect the difference in retinal function between aged WT and aged Mrp4-null mice.

Results : Microarray analysis identified 186 differentially expressed genes from the retinas of aged Mrp4-null mice compared with aged WT mice, and subsequent gene ontology and KEGG pathway analyses showed that differently expressed genes were related to lens, eye development, vision, and transcellular barrier function which are involved in metabolic pathways or viral infection pathways. No significant change in thickness was observed for each retinal layer among 4 age/genotype categories. In addition, immunohistochemical analyses of retinal cell type did not exhibit an overt change in cellular morphology or distribution among 4 age/genotype categories, either. Electroretinogram responses showed no significant differences in the amplitude or the latency between aged WT mice and aged Mrp4-null mice.

Conclusions : Although it affects gene expression profile in the mouse retina, ageing would be an insufficient stress to cause some damage to the retina in the condition of MRP4 deficiency.

This is a 2021 ARVO Annual Meeting abstract.