Development of Neurogenic Detrusor Overactivity after Thoracic Spinal Cord Injury Is Accompanied by Time-Dependent Changes in Lumbosacral Expression of Axonal Growth Regulators

Thoracic spinal cord injury (SCI) results in urinary dysfunction, which majorly affects the quality of life of SCI patients. Abnormal sprouting of lumbosacral bladder afferents plays a crucial role in this condition. Underlying mechanisms may include changes in expression of regulators of axonal growth, including chondroitin sulphate proteoglycans (CSPGs), myelin-associated inhibitors (MAIs) and repulsive guidance molecules, known to be upregulated at the injury site post SCI. Here, we confirmed lumbosacral upregulation of the growth-associated protein GAP43 in SCI animals with bladder dysfunction, indicating the occurrence of axonal sprouting. Neurocan and Phosphacan (CSPGs), as well as Nogo-A (MAI), at the same spinal segments were upregulated 7 days post injury (dpi) but returned to baseline values 28 dpi. In turn, qPCR analysis of the mRNA levels for receptors of those repulsive molecules in dorsal root ganglia (DRG) neurons showed a time-dependent decrease in receptor expression. In vitro assays with DRG neurons from SCI rats demonstrated that exposure to high levels of NGF downregulated the expression of some, but not all, receptors for those regulators of axonal growth. The present results, therefore, show significant molecular changes at the lumbosacral cord and DRGs after thoracic lesion, likely critically involved in neuroplastic events leading to urinary impairment

Tlx3 exerts direct control in specifying excitatory over inhibitory neurons in the dorsal spinal cord

© 2021 Monteiro, Miranda, Samina, Dias, Raposo, Oliveira, Reguenga, Castro and Lima. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.The spinal cord dorsal horn is a major station for integration and relay of somatosensory information and comprises both excitatory and inhibitory neuronal populations. The homeobox gene Tlx3 acts as a selector gene to control the development of late-born excitatory (dILB) neurons by specifying glutamatergic transmitter fate in dorsal spinal cord. However, since Tlx3 direct transcriptional targets remain largely unknown, it remains to be uncovered how Tlx3 functions to promote excitatory cell fate. Here we combined a genomics approach based on chromatin immunoprecipitation followed by next generation sequencing (ChIP-seq) and expression profiling, with validation experiments in Tlx3 null embryos, to characterize the transcriptional program of Tlx3 in mouse embryonic dorsal spinal cord. We found most dILB neuron specific genes previously identified to be directly activated by Tlx3. Surprisingly, we found Tlx3 also directly represses many genes associated with the alternative inhibitory dILA neuronal fate. In both cases, direct targets include transcription factors and terminal differentiation genes, showing that Tlx3 directly controls cell identity at distinct levels. Our findings provide a molecular frame for the master regulatory role of Tlx3 in developing glutamatergic dILB neurons. In addition, they suggest a novel function for Tlx3 as direct repressor of GABAergic dILA identity, pointing to how generation of the two alternative cell fates being tightly coupled.This work is a result of the project Norte-01-0145-FEDER-000008 – Porto Neurosciences and Neurologic Disease Research Initiative at I3S, supported by Norte Portugal Regional Operational Program (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (FEDER). This work was also supported by FCT – Fundação para a Ciência e Tecnologia (Grants PTDC/SAU-OBD/099886/2008 to DL and PTDC/NEU-NMC/0315/2012 to DC) and Universidade do Porto/Banco Santander Totta (Projetos Pluridisciplinares to FM). We acknowledge the support of POCI-01-0145-FEDER-022122, granted to i3S Scientific Platform Advanced Light Microscopy, member of the national infrastructure PPBI-Portuguese Platform of BioImaging.info:eu-repo/semantics/publishedVersio

DRG11 immunohistochemical expression during embryonic development in the mouse

DRG11 is a paired domain transcription factor that is necessary for the assembly of the nociceptive circuitry in the spinal cord dorsal horn. It is expressed in small dorsal root ganglion (DRG) neurons and in their projection area in the spinal cord. Drg11 knockout mice exhibit structural and neurochemical defects both at the DRG and spinal superficial dorsal horn and present reduced nociceptive responses. In this study, a polyclonal antibody against DRG11 was generated and used for a detailed systematic spatiotemporal analysis of DRG11 expression during development. DRG11 is first detected at E10.5 in the spinal dorsal horn, DRG and trigeminal ganglion, where it persists until P14-21. At the cranial level, DRG11 expression is observed from E10.5 up to the same early post-natal ages in several cranial sensory ganglia and brain nuclei. These results suggest that DRG11 is required for the establishment of the first neuronal sensory relay along development. © 2007 Wiley-Liss, Inc.Link_to_subscribed_fulltex

Several cis-regulatory elements control mRNA stability, translation efficiency, and expression pattern of Prrxl1 (paired related homeobox protein-like 1)

The homeodomain transcription factor Prrxl1/DRG11 has emerged as a crucial molecule in the establishment of the pain circuitry, in particular spinal cord targeting of dorsal root ganglia (DRG) axons and differentiation of nociceptive glutamatergic spinal cord neurons. Despite Prrxl1 importance in the establishment of the DRG-spinal nociceptive circuit, the molecular mechanisms that regulate its expression along development remain largely unknown. Here, we show that Prrxl1 transcription is regulated by three alternative promoters (named P1, P2, and P3), which control the expression of three distinct Prrxl1 5′-UTR variants, named 5′-UTR-A, 5′-UTR-B, and 5′-UTR-C. These 5′-UTR sequences confer distinct mRNA stability and translation efficiency to the Prrxl1 transcript. The most conserved promoter (P3) contains a TATA-box and displays in vivo enhancer activity in a pattern that overlaps with the zebrafish Prrxl1 homologue, drgx. Regulatory modules present in this sequence were identified and characterized, including a binding site for Phox2b. Concomitantly, we demonstrate that zebrafish Phox2b is required for the expression of drgx in the facial, glossopharyngeal, and vagal cranial ganglia.This work was supported by the Fundação para a Ciência e a Tecnologia (SFRH/BD/65300/2009 (to I. R.) and PTDC/SAU-OBD/099886/2008), COMPETE: FCOMP-01-0124-FEDER-011262, and Universidade do Porto/Banco Santander Totta (Projectos Pluridisciplinares).Peer reviewe

Development of Neurogenic Detrusor Overactivity after Thoracic Spinal Cord Injury Is Accompanied by Time-Dependent Changes in Lumbosacral Expression of Axonal Growth Regulators

Thoracic spinal cord injury (SCI) results in urinary dysfunction, which majorly affects the quality of life of SCI patients. Abnormal sprouting of lumbosacral bladder afferents plays a crucial role in this condition. Underlying mechanisms may include changes in expression of regulators of axonal growth, including chondroitin sulphate proteoglycans (CSPGs), myelin-associated inhibitors (MAIs) and repulsive guidance molecules, known to be upregulated at the injury site post SCI. Here, we confirmed lumbosacral upregulation of the growth-associated protein GAP43 in SCI animals with bladder dysfunction, indicating the occurrence of axonal sprouting. Neurocan and Phosphacan (CSPGs), as well as Nogo-A (MAI), at the same spinal segments were upregulated 7 days post injury (dpi) but returned to baseline values 28 dpi. In turn, qPCR analysis of the mRNA levels for receptors of those repulsive molecules in dorsal root ganglia (DRG) neurons showed a time-dependent decrease in receptor expression. In vitro assays with DRG neurons from SCI rats demonstrated that exposure to high levels of NGF downregulated the expression of some, but not all, receptors for those regulators of axonal growth. The present results, therefore, show significant molecular changes at the lumbosacral cord and DRGs after thoracic lesion, likely critically involved in neuroplastic events leading to urinary impairment