Expression of RBMX After Spinal Cord Injury in Rats

Identification and Characterization of Alternative Splicing Variants and Positive Selection Genes Related to Distinct Growth Rates of Antlers Using Comparative Transcriptome Sequencing

Simple Summary

The size of antlers varies among species; antlers of the wapiti (Cervus canadensis xanthopygus) grow much faster than those of its close relative the sika deer (Cervus nippon hortulorum) in the same growing period. This contrast provides a potential model for comparative studies for the identification of potent growth factors and unique regulatory systems. In the present study, the reference transcriptomes of the antler reserve mesenchyme (RM) tissue of wapiti and sika deer were constructed using single molecule real time sequencing data. The expression profiling, positive selection, and alternative splicing of the antler transcripts were compared, and interactive relationships and expression patterns of hub genes were identified and analysed. We identified that RNA Binding Motif Protein X-Linked (RBMX) gene was under strongly positive selection. One gene found to interact with RBMX was methyltransferase-like 3 (METTL3), an oncogene that could promote translation of cancer cell proteins. There was a contrasting relationship in expression level between RBMX and METTL3 genes in the RM tissue. We believe our study can provide a better understanding of rapid antler growth at the molecular level in particular and endochondral ossification in general.

Abstract

The molecular mechanism underlying rapid antler growth has not been elucidated. The contrast of the wapiti and sika deer antler provides a potential model for comparative studies for the identification of potent growth factors and unique regulatory systems. In the present study, reference transcriptomes of antler RM tissue of wapiti and sika deer were constructed using single molecule real time sequencing data. The expression profiling, positive selection, and alternative splicing of the antler transcripts were compared. The results showed that: a total of 44,485 reference full-length transcripts of antlers were obtained; 254 highly expressed transcripts (HETs) and 1936 differentially expressed genes (DEGs) were enriched and correlated principally with translation, endochondral ossification and ribosome; 228 genes were found to be under strong positive selection and would thus be important for the evolution of wapiti and sika deer; among the alternative splicing variants, 381 genes were annotated; and 4 genes with node degree values greater than 50 were identified through interaction network analysis. We identified a negative and a positive regulator for rapid antler growth, namely RNA Binding Motif Protein X-Linked (RBMX) and methyltransferase-like 3 (METTL3), respectively. Overall, we took advantage of this significant difference in growth rate and performed the comparative analyses of the antlers to identify key specific factors that might be candidates for the positive or negative regulation of phenomenal antler growth rate.

Expression of miR-210 mediated by adeno-associated virus performed neuroprotective effects on a rat model of acute spinal cord injury

Acute spinal cord injuries (ASCI) are common neural disorders in traumatology medicine. MicroRNA-210 (miR-210) plays a crucial role in cell survival, endothelial cell migration and cell regeneration. This paper is aim to validate the pathophysiological function of miR-210 on ASCI. We built a rat model of ASCI and utilized an adeno-associated virus (rAAV)-expressing miR-210 for stable over-expression of miR-210. We tested in vivo miR-210 gain of function on ASCI by microinjected rAAV-miR-210 into the rat spinal cord. We further screened the targeting genes of miR-210 by PCR array and detected related signal proteins by Western Blot and qPCR. Over-expression of miR-210 protected neurons while neurologic function scores were improved. We further identified less TUNEL-positive cells, few features of apoptosis under electron microscopy, decreased activities of caspase-3 and 8 and increased vessel count in the spinal cord from rAAV-miR-210 group. We also found rAAV-miR-210 promoted expression of angiogenesis and metastasis-related protein (VEGF and Glut1) and regulated serum levels of inflammation-related cytokines. PCR screen array showed PTP1B, target of miR-210, was significantly down-regulated and Akt phosphorylation was significantly increased in rAAV-miR-210 group. The current data suggest that over-expression of miR-210 may target PTP1B and plays a neuroprotective role on rats after ASCI.

RBMX family proteins connect the fields of nuclear RNA processing, disease and sex chromosome biology

RBMX is a ubiquitously expressed nuclear RNA binding protein that is encoded by a gene on the X chromosome. RBMX belongs to a small protein family with additional members encoded by paralogs on the mammalian Y chromosome and other chromosomes. These RNA binding proteins are important for normal development, and also implicated in cancer and viral infection. At the molecular level RBMX family proteins contribute to splicing control, transcription and genome integrity. Establishing what endogenous genes and pathways are controlled by RBMX and its paralogs will have important implications for understanding chromosome biology, DNA repair and mammalian development. Here we review what is known about this family of RNA binding proteins, and identify important current questions about their functions.

Decreased expression of LATS1 correlates with astrogliosis after spinal cord injury

Large tumor suppressor kinase 1 (LATS1) is a serine/threonine kinase of the AGC kinase family in mammals and involved in various biological processes, it is a key regulator of cell cycle progression. However, the role of LATS1 in central nervous system trauma is still unknown. In present study, we performed an acute spinal cord injury (SCI) model in adult rats and investigated the dynamic changes of LATS1 expression in the spinal cord. We found that LATS1 protein levels were significantly decreased at day 1 after injury. Meanwhile, double immunofluorescence staining showed these changes were striking in astrocytes, which were largely proliferated after SCI. In vitro, LATS1 overexpression inhibited astrocyte proliferation. Conversely, LATS1 depletion by siRNA promoted cell proliferation in primary astrocyte. Moreover, LATS1 overexpression reduced cyclin D1 expression and increased the expression of p27^kip1. In addition, LATS1 overexpression also promoted yes-associated protein 1 (YAP) phosphorylation. Our data suggested that LATS1 might play an important role in spinal cord injury and suppress astrogliosis through regulating the expression of cyclin D1, p27^kip1 and p-YAP.

Cold Shock Induced Protein RBM3 but Not Mild Hypothermia Protects Human SH-SY5Y Neuroblastoma Cells From MPP+-Induced Neurotoxicity

The cold shock protein RBM3 can mediate mild hypothermia-related protection in neurodegeneration such as Alzheimer's disease. However, it remains unclear whether RBM3 and mild hypothermia provide same protection in model of Parkinson's disease (PD), the second most common neurodegenerative disorder. In this study, human SH-SY5Y neuroblastoma cells subjected to insult by 1-methyl-4-phenylpyridinium (MPP+) served as an in-vitro model of PD. Mild hypothermia (32°C) aggravated MPP+-induced apoptosis, which was boosted when RBM3 was silenced by siRNA. In contrast, overexpression of RBM3 significantly reduced this apoptosis. MPP+ treatment downregulated the expression of RBM3 both endogenously and exogenously and suppressed its induction by mild hypothermia (32°C). In conclusion, our data suggest that cold shock protein RBM3 provides neuroprotection in a cell model of PD, suggesting that RBM3 induction may be a suitable strategy for PD therapy. However, mild hypothermia exacerbates MPP+-induced apoptosis even that RBM3 could be synthesized during mild hypothermia.

Spatiotemporal expression of FOXA1 correlates with reactive gliosis after spinal cord injury

Forkhead box A1 (FOXA1) is a member of the FOX family of transcription factors and involved in various mammalian processes. However, the expression and function of FOXA1 in central nervous system (CNS) are still with limited acquaintance. In present study, we performed an acute spinal cord injury (SCI) model in adult rats and investigated the dynamic changes of FOXA1 expression in spinal cord. We found that FOXA1 protein levels were significantly increased after SCI and we observed that the expression of FOXA1 is enhanced in the white matter. Meanwhile, double immunofluorescence staining showed that increased levels of FOXA1 were striking in astrocytes and microglia. We also examined the expression of proliferating cell nuclear antigen (PCNA), whose changes were correlated with the expression profiles of FOXA1. In vitro, FOXA1 depletion by siRNA inhibited astrocyte proliferation and migration. Meanwhile, FOXA1 knockdown also reduce cell cycle related proteins. Which indicated that FOXA1 might modulate cell cycle progression and play a crucial role in cell proliferation. Furthermore, FOXA1 knockdown also inhibited LPS-induced synthesis/secretion of IL-1β and TNF-α in primary microglia. These results indicated that FOXA1 might play an important role in pathophysiology after SCI.

RNA binding motif protein 3: a potential biomarker in cancer and therapeutic target in neuroprotection

RNA binding motif 3 (RBM3) is a highly conserved cold-induced RNA binding protein that is transcriptionally up-regulated in response to harsh stresses. Featured as RNA binding protein, RBM3 is involved in mRNA biogenesis as well as stimulating protein synthesis, promoting proliferation and exerting anti-apoptotic functions. Nowadays, accumulating immunohistochemically studies have suggested RBM3 function as a proto-oncogene that is associated with tumor progression and metastasis in various cancers. Moreover, emerging evidences have also indicated that RBM3 is equally effective in neuroprotection. In the present review, we provide an overview of current knowledge concerning the role of RBM3 in various cancers and neuroprotection. Additionally, its potential roles as a promising diagnostic marker for cancer and a possible therapeutic target for neuro-related diseases are discussed.

Chitosan scaffolds induce human dental pulp stem cells to neural differentiation: potential roles for spinal cord injury therapy

Cell-based transplantation strategies hold great potential for spinal cord injury (SCI) repair. Chitosan scaffolds have therapeutic benefits for spinal cord regeneration. Human dental pulp stem cells (DPSCs) are abundant available stem cells with low immunological incompatibility and can be considered for cell replacement therapy. The purpose of this study is to investigate the role of chitosan scaffolds in the neural differentiation of DPSCs in vitro and to assess the supportive effects of chitosan scaffolds in an animal model of SCI. DPSCs were incubated with chitosan scaffolds. Cell viability and the secretion of neurotrophic factors were analyzed. DPSCs incubated with chitosan scaffolds were treated with neural differentiation medium for 14 days and then neural genes and protein markers were analyzed by Western blot and reverse transcription plus the polymerase chain reaction. Our study revealed a higher cell viability and neural differentiation in the DPSC/chitosan-scaffold group. Compared with the control group, the levels of BDNF, GDNF, b-NGF, and NT-3 were significantly increased in the DPSC/chitosan-scaffold group. The Wnt/β-catenin signaling pathway played a key role in the neural differentiation of DPSCs combined with chitosan scaffolds. Transplantation of DPSCs together with chitosan scaffolds into an SCI rat model resulted in the marked recovery of hind limb locomotor functions. Thus, chitosan scaffolds were non-cytotoxic and provided a conducive and favorable microenvironment for the survival and neural differentiation of DPSCs. Transplantation of DPSCs might therefore be a suitable candidate for treating SCI and other neuronal degenerative diseases.

Effect of adenovirus-mediated RNA interference of IL-1β expression on spinal cord injury in rats

STUDY DESIGN

We introduced an adenoviral vector expressing interleukin-1β (IL-1β) small-hairpin RNA (shRNA) into the injured spinal cords to evaluate the therapeutic potential of IL-1β downregulation in a rat model of spinal cord injury (SCI).

OBJECTIVES

The purpose of this study was to investigate the possible protective effects of the IL-1β downregulation on traumatic SCI in rats.

SETTING

Department of Orthopedic Surgery, The Second Affiliated Hospital, Fujian Medical University, Quanzhou, People's Republic of China.

METHODS

An adenoviral shRNA targeting IL-1β was constructed and injected at the T12 section 7 days before SCI. The rats' motor functions were evaluated by the Basso-Beattie-Bresnahan (BBB) rating scale. Immunofluorescence, enzyme-linked immunosorbent assay, flow-cytometric analysis and western blots were also performed.

RESULTS

Animals downregulating IL-1β had significantly better recovery of locomotor function and less neuronal loss after SCI. In addition, IL-1β downregulation significantly decreased tumor necrosis factor-alpha (TNF-α) level and Bax expression, reduced the activity of caspase-3 and increased Bcl-2 expression after SCI.

CONCLUSION

This study demonstrated that the IL-1β downregulation may have potential therapeutic benefits for both reducing secondary damages and improving the outcomes after traumatic SCI.

Temporospatial expression of fibulin-1 after acute spinal cord injury in rats

OBJECTIVE

Fibulin-1 is a matricellular protein that plays important roles in motility inhibition in a variety of cells and blocks the proliferation of cultured neural stem cells. The biological function of fibulin-1 in the spinal cord has not been fully elucidated.

METHODS

To clarify the expressions and possible functions of fibulin-1 in spinal cord injury (SCI), we performed an acute spinal cord contusion injury model in adult rats. Our work studied the temporospatial expression patterns of fibulin-1.

RESULTS

Western blot analysis revealed that fibulin-1 levels significantly increased 5 days after spinal cord contusion. Immunohistochemistry confirmed an increased number of fibulin-1 immunopositive cells about 2 mm from the lesion site. Moreover, double immunofluorescence labeling suggested that these changes were especially prominent in neurons and microglia.

CONCLUSION

These findings suggest that fibulin-1 may be involved in neuronal apoptosis and microglial activation after SCI.

Nuclear translocation of PKM2 modulates astrocyte proliferation via p27 and -catenin pathway after spinal cord injury

Aberrant functionality of the cell cycle has been implicated in the pathology of traumatic SCI. Although it has been reported that the expressions of various cell cycle related proteins were altered significantly following SCI, detailed information on the subject remains largely unclear. The embryonic pyruvate kinase M2 (PKM2) is an important metabolic kinase in aerobic glycolysis or the warburg effect, however, its functions in central nervous system (CNS) injury remains elusive. Here we demonstrate that PKM2 was not only significantly upregulated by western blot and immunohistochemistry but certain traumatic stimuli also induced translocation of PKM2 into the nucleus in astrocytes following spinal cord injury (SCI). Furthermore, the expression levels and localization of p-β-catenin, p27, cyclin D1 and PCNA were correlated with PKM2 after SCI. In vitro, we also found that PKM2 co-immunoprecipitation with p-β-catenin and p27 respectively. Knockdown of PKM2 apparently decreased the level of PCNA, cyclinD1, p27 in primary astrocyte cells. Taken together, our findings indicate that nuclear translocation of PKM2 promotes astrocytes proliferation after SCI through modulating cell cycle signaling. These discoveries firstly uncovered the role of PKM2 in spinal cord injury and provided a potential therapeutic target for CNS injury and repair.

Expression of RBMX in the light-induced damage of rat retina in vivo

RNA-binding motif protein, X-linked (RBMX) is a 43 kDa nuclear protein in the RBM family and functions on alternative splicing of RNA. The gene encoding RBMX is located on chromosome Xq26. To investigate whether RBMX is involved in retinal neuron apoptosis, we performed a light-induced retinal damage model in adult rats. Western blotting analysis showed RBMX gradually increased, reached a peak at 12 h and then declined during the following days. The association of RBMX in retinal ganglion cells (RGCs) with light exposure was found by immunofluorescence staining. The injury-induced expression of RBMX was detected in active caspase-3 and TUNEL positive cells. We also examined the expression profiles of active caspase-3, bcl-2 and Bax, whose changes were correlated with the expression profiles of RBMX. To summarize, we uncovered the dynamic changes of RBMX in the light-induced retinal damage model for the first time. RBMX might play a significant role in the degenerative process of RGCs after light-induced damage in the retina.

RBM5 and p53 expression after rat spinal cord injury: implications for neuronal apoptosis

RBM5 (RNA-binding motif protein 5), a nuclear RNA binding protein, is known to trigger apoptosis and induce cell cycle arrest by regulating the activity of the tumor suppressor protein p53. However, its expression and function in spinal cord injury (SCI) are still unknown. To investigate whether RBM5 is involved in central nervous system injury and repair, we performed an acute SCI model in adult rats in this study. Our results showed RBM5 was unregulated significantly after SCI, which was accompanied with an increase in the levels of apoptotic proteins such as p53, Bax, and active caspase-3. Immunofluorescent labeling also showed that traumatic SCI induced RBM5 location changes and co-localization with active caspase-3 in neurons. To further probe the role of RBM5, a neuronal cell line PC12 was employed to establish an apoptotic model. Knockdown of RBM5 apparently decreased the level of p53 as well as active caspase-3, demonstrating its pro-apoptotic role in neurons by regulating expressions of p53 and caspase-3. Taken together, our findings indicate that RBM5 promotes neuronal apoptosis through modulating p53 signaling pathway following SCI.

Wogonin protects rat dorsal root ganglion neurons against tunicamycin-induced ER stress through the PERK-eIF2α-ATF4 signaling pathway

Endoplasmic reticulum (ER) stress has been demonstrated to contribute to neurodegeneration in multiple nervous system diseases. Wogonin is a flavonoid isolated from Scutellaria baicalensis root and has multiple pharmacological effects, including anti-inflammatory, antioxidant, and anticancer effects. It has a protective role in nervous system diseases; however, the pharmacological function of wogonin in the spinal cord is still with limited acquaintance. In the present study, rat dorsal root ganglion (DRG) neurons were pretreated with different concentrations of wogonin (0-100 μM) before inducing ER stress using tunicamycin (TUN) (0.75 μg/ml). Wogonin pretreatment at 75 and 100 μM had a cytoprotective effect on cells against TUN-induced toxicity. Wogonin also decreased the number of the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive DRG neurons and increased expression of superoxide dismutase (SOD), which was accompanied by decreased malondialdehyde (MDA) level. The induction of apoptosis was prevented with reduction in expression level of Bax and concomitant increase in B cell lymphoma 2 (Bcl-2) level. Furthermore, wogonin downregulated expression level of ER stress genes coding for glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), active caspase 12, transcription factor 4 (ATF4), and phosphorylation of pancreatic ER stress kinase (PERK) and eukaryotic initiation factor 2 alpha (eIF2α). The current study indicated that wogonin modulated stress-responsive genes, helping DRG neurons prevent TUN-induced ER stress through the PERK-eIF2α-ATF4 signaling pathway.

Matrix metalloproteinase-1 (MMP-1) expression in rat spinal cord injury model

Matrix metalloproteinase-1 (MMP-1), a member of the matrix metalloproteinases family, plays an integral role in extracellular matrix degradation and has been reportedly involved in the regulation of the brain or spinal cord traumatic neurovascular remodeling. Although the critical involvement of MMP-1 in the metastasis of tumors has been extensively documented, the role of MMP-1 in the pathology of neurological diseases remains largely elusive. In the present study, we established an adult rat spinal cord injury (SCI) model and investigated a potential role of MMP-1 in the pathological process of SCI. Using Western blot analysis, we identified notable expression change of MMP-1 after SCI. Immunohistochemistry showed that MMP-1 was distributed widely in rat spinal cord. Double immunofluorescence staining revealed that MMP-1 immunoreactivity was predominantly increased in neurons and astrocytes following SCI. Moreover, after injury, colocalization of MMP-1/active caspase-3 in neurons (NeuN-positive), and colocalization of MMP-1/PCNA in astrocytes (GFAP-positive) were clearly observed. We also examined the protein expression of PCNA, active caspase-3, Bcl-2, and Bax and found that the expression of the proteins was closely correlated with that of MMP-1. Taken together, our findings indicate that MMP-1 might play an important role in the regulation of neuronal apoptosis and astrocyte proliferation after SCI.

Increased Expression of TBP/TFIID after spinal cord injury in adult rats

Transcription factor IID (TFIID), as a general transcription factor, plays a pivotal role in the preinitiation complex (PIC) assembly and transcription initiation by recruiting RNA polymerase II to the promoter. The TFIID complex contains the TATA-box binding protein (TBP) and a group of conserved TAF proteins. However, its distribution and function in the central nervous system (CNS) are more diverse than previously understood. Here, we mainly investigated the spatiotemporal expression and cellular localization of TBP/TFIID during spinal cord injury (SCI) in adult rats. Western blot analysis revealed that TBP/TFIID was present in normal rat's spinal cord. It gradually increased, reached a peak at the third day after SCI, and then decreased. We observed that TBP/TFIID was widely distributed in spinal cord, mainly in neurons and glial cells. In addition, Western blot detection also showed that the third day post-injury was the proliferation peak indicated by the elevated expression of proliferating cell nuclear antigen (PCNA), a marker of proliferating cells. Importantly, injury-induced expression of TBP/TFIID was colabelled by PCNA showed the increase of TBP/TFIID expression in proliferating astrocytes and microglia. Collectively, we hypothesize that TBP/TFIID may be implicated in the proliferation of astrocytes and microglia and the recovery of neurological outcomes.

Spatiotemporal pattern of RNA-binding motif protein 3 expression after spinal cord injury in rats

RNA-binding motif protein 3 (RBM3) belongs to a very small group of cold inducible proteins with anti-apoptotic and proliferative functions. To elucidate the expression and possible function of RBM3 in central nervous system (CNS) lesion and repair, we performed a spinal cord injury (SCI) model in adult rats. Western blot analysis revealed that RBM3 level significantly increased at 1 day after damage, and then declined during the following days. Immunohistochemistry further confirmed that RBM3 immunoactivity was expressed at low levels in gray and white matters in normal condition and increased at 1 day after SCI. Besides, double immunofluorescence staining showed RBM3 was primarily expressed in the neurons and a few of astrocytes in the normal group. While after injury, the expression of RBM3 increased both in neurons and astrocytes at 1 day. We also examined the expression profiles of proliferating cell nuclear antigen (PCNA) and active caspase-3 in injured spinal cords by western blot. Importantly, double immunofluorescence staining revealed that cell proliferation evaluated by PCNA appeared in many RBM3-expressing cells and rare caspase-3 was observed in RBM3-expressing cells at 1 day after injury. Our data suggested that RBM3 might play important roles in CNS pathophysiology after SCI.

Spatiotemporal profile and essential role of RBM3 expression after spinal cord injury in adult rats

Hypoxia and other adverse conditions are usually encountered by rapidly growing cells. The RNA-binding motif protein 3 (RBM3) is induced by low temperature and hypoxia. However, its expression and function in spinal cord injury are still unclear. To investigate the certain expression and biological function in the central nervous system, we performed an acute spinal cord contusion injury (SCI) model in adult rats. Western blot analysis indicated a striking expression upregulation of RBM3 after spinal cord injury (SCI). Double immunofluorescence staining prompted that RBM3 immunoreactivity was found in astrocytes and neurons. Interestingly, RBM3 expression was increased predominantly in astrocytes. Furthermore, colocalization of RBM3 with proliferating cell nuclear antigen (PCNA) was detected in astrocytes. To further understand whether RBM3 plays a role in astrocyte proliferation, we applied lipopolysaccharide (LPS) to induce astrocyte proliferation in vitro. Western blot analysis demonstrated that RBM3 expression was positively correlated with PCNA expression following LPS stimulation. Immunofluorescence analysis showed that the expression of RBM3 was also changed following the stimulation of astrocytes with LPS, which was parallel with the data in vivo. Additionally, knocking RBM3 down with small interfering RNA (siRNA) demonstrated that RBM3 might play a significant role in the proliferation of astrocytes treated by hypoxia in vitro. These results suggest that RBM3 may be involved in the proliferation of astrocytes after SCI. To summarize, we firstly uncover the temporal and spatial expression changes of RBM3 in spinal cord injury. Our data suggest that RBM3 might be implicated in central nervous system pathophysiology after SCI.

Up-regulation of FoxN4 expression in adult spinal cord after injury

FoxN4 (forkhead box N4), which is a transcription factor involved in developing spinal cord and spinal neurogenesis, implied important roles in the central nervous system (CNS). However, its expression and function in the adult CNS lesion are still unclear. In this study, we established a spinal cord injury (SCI) model in adult rats and investigated the expression of FoxN4 in the spinal cord. Western blot analysis revealed that FoxN4 was present in normal spinal cord. It gradually increased, peaked at day 3 after SCI, and then decreased during the following days. Immunohistochemistry further confirmed that FoxN4 was expressed at low levels in gray and white matters in normal condition and increased after SCI. Double immunofluorescence staining showed that FoxN4 is located on neurons and astrocytes, and FoxN4 expression was increased progressively in reactive astrocytes within the vicinity of the lesion, predominately in the white matter. In addition, almost all FoxN4-positive cells also expressed nestin or PCNA. Our data suggested that FoxN4 might play important roles in CNS pathophysiology after SCI.