Developmental Cytoplasmic-to-Nuclear Translocation of RNA-Binding Protein HuR Is Required for Adult Neurogenesis

Although neurogenesis in the adult brain recapitulates processes that occur during embryonic development, adult neurogenesis exhibits distinct characteristics from its embryonic counterpart. However, the intrinsic mechanism underlying the differential regulation of neurogenesis between these two stages remains unclear. Herein, we show that the ablation of RNA-binding protein HuR in neural stem cells (NSCs) impairs adult, but not embryonic, neurogenesis. HuR is predominantly expressed in the cytoplasm of embryonic NSCs but translocates into the nucleus of adult NSCs. Transcriptomic analysis of HuR-deficient adult NSCs revealed that nuclear HuR primarily regulates alternative splicing of numerous premRNA transcripts, including focal adhesion kinase (FAK). HuR-deficient adult NSCs generate increased FAK mRNA isoforms with shorter 5' UTRs, leading to enhanced FAK mRNA translation and hyperactivated FAK signaling, and inhibition of FAK ameliorates defective adult neurogenesis and impaired hippocampus-dependent learning in HuR-deficient mice. Taken together, these findings reveal novel mechanistic insights into the differential regulation of embryonic and adult neurogenesis through developmental cytoplasmic-to-nuclear translocation of HuR in NSCs. Overall design: Total RNA was extracted from HuRf/f aNSCs infected with lenti-dCre or lenti-Cre using TRIzol (Invitrogen). The integrity of the extracted total RNA was analyzed using Agilent 2100 Bioanalyzer (Agilent Technologies, Santa Clara, CA, USA). The samples with RNA Integrity Number (RIN) = 7 were subjected to the subsequent analysis. The libraries were constructed using TruSeq Stranded mRNA LTSample Prep Kit (Illumina, San Diego, CA, USA) according to the manufacturer's instructions. The standard Illumina protocol was used to prepare the libraries for RNA-Seq. RNA-seq was performed using Illumina HiSeq2500 ?>?45 million 2?×?100 reads per sample was produced and alignment was performed using mouse genome database GRCm38 version 67. Only uniquely and properly mapped read pairs were used for further analysis. FPKM value of each gene was calculated using cufflinks, and the read counts of each gene were obtained by htseq-count. Differentially expressed genes (DEGs) were identified using the DESeq (2012) functions estimateSizeFactors and nbinomTest. P value < 0.05 and foldChange >2 or foldChange < 0.5 was set as the threshold for significantly differential expression. Hierarchical cluster analysis of DEGs was performed to explore genes expression pattern. GO enrichment and KEGG pathway enrichment analysis of DEGs were respectively performed using R based on the hypergeometric distribution. The alternatively splicing analysis of differentially regulated transcripts isoforms or exons was performed using multivariate analysis of transcript splicing (MATS).