Project description:Here, we show that epidural electrical stimulation (EES) of the lumbar spinal cord applied during neurorehabilitation (EESREHAB) restored walking in nine people with chronic spinal cord injury (SCI). This recovery involved a reduction of the metabolic activity in the lumbar spinal cord during walking. We hypothesized that this unexpected reduction reflects activity-dependent selection of specific neuronal subpopulations that become essential to walk after SCI. To identify these putative neurons, we modelled the technological and therapeutic features underlying EESREHAB in mice. We applied single-nucleus RNA sequencing and spatial transcriptomics to the spinal cord of these mice to chart a spatially-resolved molecular atlas of recovery from paralysis. We then employed cell type and spatial prioritization to uncover the neurons involved in the recovery of walking. A single population of excitatory interneurons nested within intermediate laminae emerged. Although these neurons were not necessary to walk before SCI, we demonstrate that they are essential to regain walking following SCI. In turn, augmenting their activity instantly phenocopied the recovery of walking enabled by EESREHAB. We thus identified a recovery-organizing neuronal subpopulation that is necessary and sufficient to regain walking after SCI. Moreover, our methodology establishes a framework to identify the neurons producing complex behaviours using molecular cartography.
Project description:Here, we show that epidural electrical stimulation (EES) of the lumbar spinal cord applied during neurorehabilitation (EESREHAB) restored walking in nine people with chronic spinal cord injury (SCI). This recovery involved a reduction of the metabolic activity in the lumbar spinal cord during walking. We hypothesized that this unexpected reduction reflects activity-dependent selection of specific neuronal subpopulations that become essential to walk after SCI. To identify these putative neurons, we modelled the technological and therapeutic features underlying EESREHAB in mice. We applied single-nucleus RNA sequencing and spatial transcriptomics to the spinal cord of these mice to chart a spatially-resolved molecular atlas of recovery from paralysis. We then employed cell type and spatial prioritization to uncover the neurons involved in the recovery of walking. A single population of excitatory interneurons nested within intermediate laminae emerged. Although these neurons were not necessary to walk before SCI, we demonstrate that they are essential to regain walking following SCI. In turn, augmenting their activity instantly phenocopied the recovery of walking enabled by EESREHAB. We thus identified a recovery-organizing neuronal subpopulation that is necessary and sufficient to regain walking after SCI. Moreover, our methodology establishes a framework to identify the neurons producing complex behaviours using molecular cartography.
Project description:Although axon regeneration can now be induced experimentally across anatomically complete spinal cord injury (SCI), restoring meaningful function after such injuries has been elusive. This failure contrasts with the spontaneous, naturally occuring repair that restores walking after severe but incomplete SCI. Here, we applied projection-specific and comparative single-nucleus RNA sequencing to uncover the transcriptional phenotype and connectome of neuronal subpopulations involved in natural spinal cord repair. We identified a molecularly defined population of excitatory projection neurons in the thoracic spinal cord that extend axons to the lumbar spinal cord where walking execution centers reside. We show that regrowing axons from these specific neurons across anatomically complete SCI and guiding them to reconnect with their appropriate target region in the lumbar spinal cord restores walking in mice. These results demonstrate that mechanism-based repair strategies that recapitulate the natural topology of molecularly defined neuronal subpopulations can restore neurological functions. Expanding this principle to different classes of neurons across the central nervous system may unlock the framework to achieve complete repair of the injured spinal cord.
Project description:U1 snRNA is the small nuclear RNA that services as the backbone of U1 snRNP. Removing intron from pre-mRNA to produce mature mRNA is the core function of the U1 snRNA. As one of the most abundant small noncoding RNA in human cells – estimated to be in the region of 1x10^6 copies per human cell (Hela) – U1 snRNA level is much more abundant than the other snRNAs. However, the potential role of the different amounts of the snRNAs is still unknown. To study the function of U1 snRNA in human neurons, we used lentivirus vector to overexpression U1 snRNA. We analyzed the gene expression change and identified target genes of U1 snRNA overexpression. We uncovered a novel role of U1 snRNA in regulating gene expression in human neurons.
Project description:Spliceosomal snRNA are key components of small nuclear ribonucleoprotein particles (snRNPs), the building blocks of the spliceosome. The biogenesis of snRNPs is a complex process involving multiple cellular and subcellular compartments, the details of which are yet to be described. In short, the snRNA is exported to the cytoplasm as 3‘-end extended precursor (pre-snRNA), where it acquires a heptameric Sm ring. The SMN complex which catalyses this step, recruits Sm proteins and assembles them around the pre-snRNA at the single stranded Sm site. After additional modification, the complex is re-imported into the nucleus where the final maturation step occurs. Our modeling suggests that during the cytoplasmic stage of maturation pre-snRNA assumes a compact secondary structure containing Near Sm site Stem (NSS) which is not compattible with the formation of the Sm ring. To validate our in silico predictions we employed selective 2'-hydroxyl acylation analyzed by primer extension sequencing (SHAPE-Seq) on U2 snRNA in vivo, ex vivo and in vitro, and U4 pre-snRNA in vitro. For the in vivo experiment HeLa cells were incubated for 10 min at 37°C with NAI or DMSO to final concentration 200 mM. RNA was isolated using Trizol (Sigma) and 200 µl chloroform and precipitated with ethanol at -20°C overnight. For the ex vivo experiment, RNA was isolated from HeLa cells after Protease K treatment at room temperature for 45 min. After incubation, RNA was isolated using equilibrated phenol/chloroform/isoamyl alcohol buffered by folding buffer (110 mM HEPES pH 8.0, 110 mM KCl, 11 mM MgCl2) and cleaned on a PD-10 column according to the manufacturer’s instructions. Isolated RNA was treated with 100mM NAI or DMSO for 10 min at 37°C. For the in vitro experiment, U2WT and U4 pre-snRNA were transcribed by T7 polymerase followed by DNase I (30 min at 37 °C) and Proteinase K (30 min at 37°C) treatments. U2 snRNA was purified on 30 kDa Amicon columns, folded for 30 min at 37°C in 57 mM MgCl2 and incubated with 100 mM NAI at 37°C for 10 min. DMSO was used as a negative control. U4 pre-snRNA was purified on Superdex 200 Increase 10/300GL, folded for 30 min at 37°C in 60 mM MgCl2 and incubated with 100 mM NAI at 37°C for 10 min. DMSO was used as a negative control. All prepared RNA samples (in vitro, ex vivo, in vivo) were used for reverse transcription with the gene-specific primer 5’-CGTTCCTGGAGGTACTGCAA for U2 snRNA and 5’- AAAAATTCAGTCTCCG for U4 pre-snRNA. We used SHAPE MaP buffer (50 mM Tris-HCl pH 8.0, 75 mM KCl, 10 mM DTT, 0.5 mM dNTP, 6 mM MnCl2) and SuperScript II (Invitrogen). Amplicons for snRNAs were generated using gene-specific forward and reverse primers. Importantly, the primers include Nextera adaptors required for downstream library construction. PCR reaction products were cleaned using Monarch PCR&DNA Clean-up Kits. Remaining Illumina adaptor sequences were added using the PCR MasterMix and index primers provided in the NexteraXT DNA Library Preparation Kit (Illumina) according to the manufacturer’s protocol. Libraries were quantified using Qubit (Invitrogen) and BioAnalyzer (Agilent). Amplicons were sequenced on a NextSeq 500/550 platform using a 150 cycle mid-output kit. All sequencing data was analyzed using the ShapeMapper 2 analysis pipeline1. The ‘—amplicon’ and ‘—primers’ flags were used, along with sequences of gene-specific handles PCR primers, to ensure primer binding sites are excluded from reactivity calculations. Default read-depth thresholds of 5000x were used. Analysis of statistically significant reactivity differences between ex vivo and in vivo-determined SHAPE reactivities was performed using the DeltaSHAPE automated analysis tool and default settings2. 1. Busan, S. & Weeks, K.M. Accurate detection of chemical modifications in RNA by mutational profiling (MaP) with ShapeMapper 2. RNA 24, 143-148 (2018). 2. Smola, M.J., Rice, G.M., Busan, S., Siegfried, N.A. & Weeks, K.M. Selective 2'-hydroxyl acylation analyzed by primer extension and mutational profiling (SHAPE-MaP) for direct, versatile and accurate RNA structure analysis. Nat Protoc 10, 1643-69 (2015).