RNA-binding Factors Implicated in Neurogenesis, Alzheimer's Disease, and other Neurodegenerative Pathologies

National Institute On Aging

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Abstract

Several studies are underway in the RNA Regulation Section to investigate the gene expression programs that influence neuronal physiology and pathology, with particular emphasis on neurodegeneration. During this review period, we have studied the transcriptomic programs of senescent cells that modulate amyloid plaques in Alzheimers disease (AD). We previously reported that the levels of amyloid precursor protein (APP), which is cleaved to release the Alzheimers disease hallmark peptide Abeta, was regulated by RBPs FMRP (fragile X mental retardation protein) and hnRNP C (heterogeneous nuclear ribonucleoprotein C) (Lee et al., Nature Structural and Molecular Biology, 2010), as well as by the RBP HuD (Kang et al., Cell Reports 2014) led us to propose that HuD jointly promotes the production of APP and the cleavage of its amyloidogenic fragment, Abeta. We later identified heterogeneous nuclear ribonucleoproteins H1 and H2(HNRNPH) as RBPs specifically capable of interacting with the spliced RNA segment (exon 7) of Trf2 pre-mRNA. HNRNPH proteins prevent the production of the short isoform of Trf2 mRNA, as HNRNPH silencing selectively elevates TRF2-S levels. Accordingly, HNRNPH levels decline while TRF2-S levels increase during neuronal differentiation. Using CRISPR/Cas9-mediated deletion of hnRNPH2 we found a selective acceleration of the NGF-triggered differentiation of rat pheochromocytoma cells into neurons. We propose that HNRNPH is a splicing regulator of Trf2 pre-mRNA that prevents the expression of TRF2-S, a factor implicated in neuronal differentiation (Grammatikakis et al., Cell Reports, 2016). A follow-up review discussed the distinct nuclear and cytoplasmic functions of TRF2 (Grammatikakis et al., Cell Cycle 2016). We also reviewed the role of a lncRNA, Pnky, which influenced neural stem cell differentiation by binding to PTBP1 (Grammatikakis et al., Stem Cell Investigation, 2016). In this review period, we have identified senescent oligodendrocyte precursor cells (OPCs) in the vicinity of amyloid beta plaques and have characterized their gene expression programs and their impact on the size, number, and pathology of plaques. We discovered that eliminating senescent cells alleviated AD pathogenesis and improved learning and memory in an AD mouse model (Zhang et al., Nature Neuroscience, 2019). of compiled and discussed long noncoding RNAs implicated in Alzheimers disease. In ongoing studies, we are investigating the role of extracellular vesicles from this senescent population, both as mediators of AD pathology and as markers of AD.