In vivo post‐transcriptional regulation of GAP‐43 mRNA by overexpression of the RNA‐binding protein HuD

• Published in: Journal of neurochemistry 2006-02, Vol.96 (3), p.790-801
• Main Authors: Bolognani, Federico, Tanner, Daniel C., Merhege, Melissa, Deschênes‐Furry, Julie, Jasmin, Bernard, Perrone‐Bizzozero, Nora I.
• Format: Article
• Language: English
• Subjects: Animals; Binding sites; Biological and medical sciences; Blotting, Northern - methods; Brain - anatomy & histology; Brain - metabolism; Cell structures and functions; Cytoskeleton, cytoplasm. Intracellular movements; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; ELAV; ELAV Proteins - genetics; ELAV Proteins - metabolism; ELAV-Like Protein 4; Fundamental and applied biological sciences. Psychology; GAP-43 Protein - genetics; GAP-43 Protein - metabolism; GAP‐43; Gene expression; Gene Expression - physiology; Gene Expression Regulation - physiology; HuD; Humans; Immunohistochemistry - methods; Immunoprecipitation - methods; In Situ Hybridization - methods; Medical sciences; Mice; Mice, Transgenic; Molecular and cellular biology; mRNA stability; Neurology; Neurons; Proteins; Ribonucleic acid; RNA; RNA Processing, Post-Transcriptional - physiology; RNA, Messenger - metabolism; Time Factors; transgenic mice
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2005.03607.x

HuD is a neuronal‐specific RNA‐binding protein that binds to and stabilizes the mRNAs of growth‐associated protein‐43 (GAP‐43) and other neuronal proteins. HuD expression increases during brain development, nerve regeneration, and learning and memory, suggesting that this protein is important for controlling gene expression during developmental and adult plasticity. To examine the function of HuD in vivo, we generated transgenic mice overexpressing human HuD under the control of the calcium–calmodulin‐dependent protein kinase IIα promoter. The transgene was expressed at high levels throughout the forebrain, including the hippocampal formation, amygdala and cerebral cortex. Using quantitative in situ hybridization, we found that HuD overexpression led to selective increases in GAP‐43 mRNA in hippocampal dentate granule cells and neurons in the lateral amygdala and layer V of the neorcortex. In contrast, GAP‐43 pre‐mRNA levels were unchanged or decreased in the same neuronal populations. Comparison of the levels of mature GAP‐43 mRNA and pre‐mRNA in the same neurons of transgenic mice suggested that HuD increased the stability of the transcript. Confirming this, mRNA decay assays revealed that the GAP‐43 mRNA was more stable in brain extracts from HuD transgenic mice than non‐transgenic littermates. In conclusion, our results demonstrate that HuD overexpression is sufficient to increase GAP‐43 mRNA stability in vivo.