Age-related MicroRNA Profiling In Rat Brain

Background and Aims:Brain aging remains one of the great mysteries of biogerontology.Present evidence neither reveal exactly what breaks down during aging process,nor does discover the mechanistic causes of brain function decline and when such failure occurs.The increasing recognition that microRNAs(miRNAs),a family of highly conserved small non-coding RNAs,function as crucial regulators of gene expression has implicated these molecules in modulating age-related signaling pathways and may contribute to brain function loss and neurodegenerative disorders.However,a critical challenge is that the known rat miRNAs seem to be far from exhaustive,as the 728 mature miRNAs of rats collected in the miRBase version 20 are far fewer than those of mice(1908)and humans(2578).This will be the great hindrance to obtain a more global view of age-related changes of miRNAs and the molecular principles of brain aging in rats.Therefore,this study will profile the miRNAs and their regulating mechanisms in rat brains based on deep-sequencing.Methods:Aging rats models were constructed based on Specific-pathogen-free male Sprague-Daley rats,followed by histological analysis,miRNAs extraction,deep sequencing,bioinformaticsanalysis and Q-PCR validation.Results:(1)After more than two years experiment,different aged(6 months,14 months ans 22 months)rats models with no obvious pathologic features were successful constructed.(2)547 known miRNAs and 171 novel miRNA candidates were identified using high-throughput deep-sequencing.(3)The profiling expression of rat brain miRNAs did not show a progressive decline with advanced aging,but rather a quadratic curve related with age.(4)The fold changes between Q-PCR and deep sequencing were consistent.(5)The bioinformatics analysis of the targets of known matured miRNAs revealed that many target genes played critical roles in the signaling pathways related with brain aging and neurodegenerative diseases.(6)Most of the novel miRNAs were conserved with known matured miRNAs in other species,and their target genes were also involved in the molecular nodes directly relevant to the manifestations of aging and neurodegenerativediseases.Conclusions:(1)This deep sequencing study has identified 171 potential novel miRNAs in rat brains,making evaluation of the full regulating mechanism for age-related genes or pathways feasible.(2)Age is a critical regulator for miRNA expression,and the age-related decline of miRNA expression is not a progressive process,but rather a quadratic one.(3)Age-regulated miRNAs and novel miRNAs are predicted to target genes involving in nodes of signaling pathways relevant to brain aging and neurodegenerative diseases.