Abstract
Purpose :
Aβ42 peptide aggregation and drusen formation are due in part to the inability of homeostatic clearance mechanisms to remove these self-aggregating, pro-inflammatory neurotoxins. Aβ42 ubiquitinization is part of a cellular clearance mechanism essential for proteostatic pathways that regulate protein degradation. Ubiquitin conjugase (UBE2A; chr Xq24) was found to be significantly down-regulated in AD and AMD. Integrated mRNA-miRNA-array and RNA-sequencing analysis suggested that an up-regulated, NF-kB-sensitive miRNA-7 (chr 9q21.32) may be responsible for UBE2A deficits. The purpose of this study was to examine the nature of the miRNA-7-mediated mechanism of UBE2A down-regulation in AD and AMD.
Methods :
anti-miRNA, bioinformatics, mRNA-miRNA arrays; NF-kB inhibitors, LED-Northern dot blot, RNA sequencing, transfection, retinal and brain cell cultures, RNaseR, transgenic murine models.
Results :
miRNA-7 is an evolutionary ancient microRNA abundant in the CNS that associates with a circRNA for miRNA-7 (ciRS-7). ciRS-7 contains ~70 tandem anti-miRNA-7 sequences; ciRS-7 (~1400 nt) thereby acts as a kind of endogenous, competing, anti-complementary miRNA “sponge” to adsorb, and hence quench miRNA-7 functions. Deficits in ciRS-7 'sponging' might be expected to increase miRNA-7, as is observed in AD and AMD, to ultimately contribute to the down-regulation of miRNA-7-sensitive mRNA targets such as UBE2A.
Conclusions :
Our understanding of the specialized functions for CNS miRNAs continues to evolve. These data are the first to show an up-regulated miRNA-7 coupled to UBE2A down-regulation in AD and AMD, CNS diseases associated with Aβ42 accumulation. These data support six novel observations: that (i) an NF-kB-sensitive, miRNA-7 modulation of UBE2A contributes to Aβ42 clearance; (ii) gene products encoded on two different chromosomes (miRNA-7 at chr9q21.32; UBE2A at chrXq24) orchestrate a complex Aβ42 clearance system; (iii) this miRNA-7-UBE2A mechanism is inducible from outside of the cell; (iv) circRNAs, a naturally occurring class of miRNA regulators are abundant in the brain and retinal transcriptome; (v) deficits in ciRS-7 up-regulates miRNA-7, as is observed in AD and AMD; and (vi) anti-NF-kB and/or AM-based therapeutic strategies may be useful against defects in UBE2A-linked Aβ42 peptide clearance.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.