Reptiles are the most morphologically and physiologically diverse tetrapods, and have undergone 300 million years of adaptive evolution. Within the reptilian tetrapods, geckos possess several interesting features, including the ability to regenerate autotomized tails and to climb on smooth surfaces. Here we sequence the genome of Gekko japonicus (Schlegel's Japanese Gecko) and investigate genetic elements related to its physiology. We obtain a draft G. japonicus genome sequence of 2.55 Gb and annotated 22,487 genes. Comparative genomic analysis reveals specific gene family expansions or reductions that are associated with the formation of adhesive setae, nocturnal vision and tail regeneration, as well as the diversification of olfactory sensation. The obtained genomic data provide robust genetic evidence of adaptive evolution in reptiles.

Peripheral nerve injury is a common clinical problem. Nerve growth factor (NGF) promotes peripheral nerve regeneration, but its clinical applications are limited by several constraints. In this study, we found that the time-dependent expression profiles of eight let-7 family members in the injured nerve after sciatic nerve injury were roughly similar to each other. Let-7 microRNAs (miRNAs) significantly reduced cell proliferation and migration of primary Schwann cells (SCs) by directly targeting NGF and suppressing its protein translation. Following sciatic nerve injury, the temporal change in let-7 miRNA expression was negatively correlated with that in NGF expression. Inhibition of let-7 miRNAs increased NGF secretion by primary cultured SCs and enhanced axonal outgrowth from a coculture of primary SCs and dorsal root gangalion neurons. In vivo tests indicated that let-7 inhibition promoted SCs migration and axon outgrowth within a regenerative microenvironment. In addition, the inhibitory effect of let-7 miRNAs on SCs apoptosis might serve as an early stress response to nerve injury, but this effect seemed to be not mediated through a NGF-dependent pathway. Collectively, our results provide a new insight into let-7 miRNA regulation of peripheral nerve regeneration and suggest a potential therapy for repair of peripheral nerve injury.

The regulation of Schwann cell (SC) responses to injury stimuli by microRNAs (miRNAs) remains to be explored. Here, we identified 17 miRNAs that showed dynamic expression alterations at five early time points following rat sciatic nerve resection. Then we analyzed the expression pattern of 17 miRNAs, and integrated their putative targets with differentially expressed mRNAs. The resulting 222 potential targets were mainly involved in cell phenotype modulation, including immune response, cell death and cell locomotion. Among 17 miRNAs, miR-182 expression was up-regulated. The enhanced expression of miR-182 was correlated with nerve injury-induced phenotype modulation of SCs. Further investigation revealed that fibroblast growth factor 9 (FGF9) and neurotrimin (NTM) were two direct targets of miR-182 in SCs, with miR-182 binding to the 3′-untranslated region of FGF9 and NTM. Silencing of FGF9 and NTM recapitulated the inhibiting effect of miR-182 mimics on SC proliferation and migration, respectively, whereas enforced knockdown of FGF9 and NTM reversed the promoting effect of miR-182 inhibitor on SC proliferation and migration, respectively. Our data indicate that nerve injury inhibits SC proliferation and migration through rapid regulation of miR-182 by targeting FGF9 and NTM, providing novel insights into the roles of miRNAs in nerve injury and repair.

Summary microRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the post-transcriptional level. Their roles in regulating the responses of Schwann cells (SCs) to injury stimuli remain unexplored. Here we report dynamic alteration of miRNA expression following rat sciatic nerve injury using microarray analysis. We harvested the proximal nerve stumps and identified 77 miRNAs that showed significant changes at four time points after nerve transection. Subsequently, we analyzed the expression pattern of miRNA, selected one significant profile, and then integrated putative miRNA targets with differentially expressed mRNA yielding 274 potential targets. The 274 targets were mainly involved in cell proliferation, cell locomotion and cellular homeostasis that were known to play important roles in modulating cell phenotype. The upregulation of the miR-221 and miR-222 cluster (miR-221/222) was found to correlate with the injury-induced SC phenotypic modulation. Enhanced expression of miR-221/222 could promote SC proliferation and migration in vitro, whereas silencing their expression resulted in a reduced proliferation and migration. Further studies revealed that longevity assurance homologue 2 (LASS2) was a direct target of miR-221/222 in SCs because miR-221/222 bound directly to the 39-untranslated region of LASS2, thus reducing both mRNA and protein levels of LASS2. Silencing of LASS2 recapitulated the effects of miR-221/222 mimics, whereas enforced knockdown of LASS2 reversed the suppressive effects of miR-221/222 inhibitors. Our findings indicate that injury promotes SC proliferation and migration through the regulation of miR-221/222 by targeting LASS2, and provide new insights into the role of miRNAs in nerve regeneration.

We analyzed 314,254 soybean expressed sequence tags (ESTs), including 29,540 from our laboratory and 284,714 from GenBank. These ESTs were assembled into 56,147 unigenes. About 76.92% of the unigenes were homologous to genes from Arabidopsis thaliana ( Arabidopsis). The putative products of these unigenes were annotated according to their homology with the categorized proteins of Arabidopsis. Genes corresponding to cell growth and/or maintenance, enzymes and cell communication belonged to the slow-evolving class, whereas genes related to transcription regulation, cell, binding and death appeared to be fast-evolving. Soybean unigenes with no match to genes within the Arabidopsis genome were identified as soybean-specific genes. These genes were mainly involved in nodule development and the synthesis of seed storage proteins. In addition, we also identified 61 genes regulated by salicylic acid, 1,322 transcription factor genes and 326 disease resistance-like genes from soybean unigenes. SSR analysis showed that the soybean genome was more complex than the Arabidopsis and the Medicago truncatula genomes. GC content in soybean unigene sequences is similar to that in Arabidopsis and M. truncatula. Furthermore, the combined analysis of the EST database and the BAC-contig sequences revealed that the total gene number in the soybean genome is about 63,501.

BackgroundAstrocytes act as immune effector cells with the ability to produce a wide array of chemokines and cytokines in response to various stimuli. Macrophage migration inhibitory factor (MIF) is inducibly expressed in injured spinal cord contributing to excessive inflammation that affects motor functional recovery. Unknown is whether MIF can facilitate inflammatory responses through stimulating release of chemokines from astrocytes following spinal cord injury.MethodsFollowing the establishment of the contusion spinal cord injury rat model, the correlation of chemokine (C-C motif) ligand 5 (CCL5) expression with that of MIF was assayed by Western blot, ELISA, and immunohistochemistry. Immunoprecipitation was used to detect MIF interaction with membrane CD74 receptor. Intracellular signal transduction of MIF/CD74 axis was analyzed by transcriptome sequencing of primary astrocytes and further validated by treatment of various inhibitors. The effects of CCL5 released by astrocytes on macrophage migration were performed by transwell migration assay. The post-injury locomotor functions were assessed using the Basso, Beattie, and Bresnahan (BBB) locomotor scale.ResultsThe protein levels of chemokine CCL5/RANTES were remarkably increased in the astrocytes of rat injured spinal cord, in parallel with the expression of MIF. Treatment of MIF inhibitor 4-IPP in the lesion sites resulted in a significant decrease of CCL5 protein levels. In vitro study revealed MIF was capable of facilitating CCL5 production of astrocytes through interaction with CD74 membrane receptor, and knockdown of this receptor attenuated such effects. Production of CCL5 in astrocytes was significantly blocked by inhibitor of c-Jun N-terminal kinase, rather than by those of ERK and P38. Recombinant CCL5 protein was found to be more effective in promoting migration of M2- compared to M1-type macrophages.ConclusionCollectively, these data reveal a novel function of MIF in regulation of CCL5 release from astrocytes, which in turn favors for recruitment of inflammatory cells to the injured site of the spinal cord, in association with activation of excessive inflammation.Electronic supplementary materialThe online version of this article (10.1186/s12974-018-1297-z) contains supplementary material, which is available to authorized users.

Following peripheral nerve injury, transcriptional responses are orchestrated to regulate the expression of numerous genes in the lesioned nerve, thus activating the intrinsic regeneration program. To better understand the molecular regulation of peripheral nerve regeneration, we aimed at investigating the transcriptional landscape of dorsal root ganglia (DRGs) after sciatic nerve transection in rats. The cDNA microarray analysis was used to identify thousands of genes that were differentially expressed at different time points post nerve injury (PNI). The results from Euclidean distance matrix, principal component analysis, and hierarchical clustering indicated that 2 nodal transitions in temporal gene expressions could segregate 3 distinct transcriptional phases within the period of 14 d PNI. The 3 phases were designated as “a stress response phase”, “a pre-regeneration phase”, and “a regeneration phase”, respectively, by referring to morphological observation of post-nerve-injury changes. The gene ontology (GO) analysis revealed the distinct features of biological process, cellular component, and molecular function at each transcriptional phase. Moreover, Ingenuity Pathway Analysis suggested that differentially expressed genes, mainly transcription factors and genes associated with neurite/axon growth, might be integrated into regulatory networks to mediate the regulation of peripheral nerve regeneration in a highly cooperative manner.

Background: HMGB1 in spontaneously regenerating spinal cord does not trigger the inflammation in contrast to those in injured mammalian cords. Results: Gecko HMGB1 paralogs failed to interact with TLR2 and TLR4 but do with RAGE receptors to activate the signaling pathway. Conclusion: HMGB1 is beneficial for spontaneous spinal cord regeneration by eliciting negligible inflammation and promoting oligodendrocyte migration. Significance: HMGB1 displays distinct functions in regenerative vertebrates.