RNA sequencing data and the data preprocessing
The miRNA transcription profile of GSE82195 and the mRNA transcription profile of GSE82196 [7] (Illumina HiSeq 2500) including dorsal root ganglion (DRG) tissue samples of normal adult rat (none, n = 6), 10 weeks post-pyramidotomy, intramuscular AAV-1 GFP (injury, n = 6) and 10 weeks post-pyramidotomy, intramuscular AAV-1 prepro-neurotrophin-3 (NT-3, n = 6) were downloaded from the Gene Expression Omnibus (GEO; http://www.ncbi.nlm.nih.gov/geo/). The preprocess Core package in R language (version 1.44, https://www.bioconductor.org/packages/devel/bioc/html/preprocessCore.html) was employed to perform the background correction and the normalization [9].
Differentilly Expressed Rnas Analysis
Limma package in R language [10] (Version 3.34.0, https://bioconductor.org/packages/release/bioc/html/limma.html) to screen the differentilly expressed RNAs (DERs) including differentially expressed genes (DEGs) and differentially expressed miRNA (DEmiRNAs) between group injury and group none, as well as the DEGs and DEmiRNAs between group NT-3 and group injury. We used the FDR-value < 0.05 and |log2 FC| > 0.5 as the cutoff criteria for DEGs and DEmiRNAs. Furthermore, the intersection DERs were also screened. The pheatmap package in R [11] (version 1.0.8, https://cran.r-project.org/package=pheatmap) was employed to conduct the bidirectional hierarchical clustering.
Clustering Analysis
With the aforementioned cut-off criteria, two clusters were obtained including cluster 1 (44 DERs, containing 10 miRNAs and 4 mRNAs) and cluster 2 (36 DERs, containing 10 miRNAs and 26 mRNAs) (Table 1). DREs in cluster 1 were firstly significantly downregulated in group injury and subsequently were significantly upregulated in group NT-3. DERs in cluster 2 were firstly upregulated in group injury and subsequently downregulated in group NT-3 (Fig. 3).
Table 1
cluster1 | cluster2 |
Adsl | Abca4 |
Aurkb | Aptx |
Bace2 | Bdh2 |
Chdh | Cybrd1 |
Col9a1 | Dmac2 |
Cxcl14 | Drc1 |
Dhh | Fgd1 |
Ehd4 | Fli1 |
Epha10 | Frzb |
Etv5 | Gclc |
Fam83d | Ghsr |
Fam83f | Id1 |
Gas7 | Mrnip |
Gjb1 | Nebl |
Gucy2d | Nme3 |
Loxl4 | Oprl1 |
Map4k4 | Pdcd2l |
Meox1 | Pgf |
Pdia5 | Ppl |
Plk2 | Prkag3 |
Plxdc1 | Rbpms2 |
Ppp4r1 | rno-let-7d-3p |
Ptger4 | rno-miR-182 |
Radil | rno-miR-187-5p |
Rasa3 | rno-miR-27a-3p |
Reln | rno-miR-29b-1-5p |
rno-miR-145-5p | rno-miR-30e-3p |
rno-miR-146b-5p | rno-miR-379-3p |
rno-miR-1839-5p | rno-miR-455-3p |
rno-miR-217-5p | rno-miR-505-5p |
rno-miR-3072 | rno-miR-672-3p |
rno-miR-344b-1-3p | Slc22a25 |
rno-miR-3594-3p | Slc4a4 |
rno-miR-381-3p | Slc6a6 |
rno-miR-666-5p | Slc9a5 |
rno-miR-667-5p | Smpd2 |
Sh3rf1 | |
Shbg | |
Shc4 | |
Mirna-mrna Regulatory Networks Construction
By using DERs in the clusters, the the miRNA-mRNA regulatory network was constructed. Firstly, DEmiRNA targets was predicted using starBase database (Version 2.0, http://starbase.sysu.edu.cn/). Secondly, the miRNA-mRNA pair with the negative correlation were retained. lastly, the screened miRNA-mRNA pairs were visualized using Cytoscape software with the DEmiRNAs in cluster 1 and their target DEGs in cluster 2, as well as using the DEmiRNAs in cluster 2 and their target DEGs in cluster 1 (Version 3.6.1, http://www.cyto scape.org) [13]. DAVID (version 6.8, https://david.ncifcrf.gov/) was used to perform the GO and KEGG pathway enrichment for the mRNA in the network [14].
Central Nervous System Injury Related Kegg Pathway Screening
In the CTD database, 13 KEGG pathways were searched, among which Neuroactive ligand-receptor interaction (including two genes: OPRL1 and GHSR in cluster 2) was intersected with enriched KEGG pathway for the DEGs in the miRNA-mRNA regulatory network. GHSR could be the target of rno-miR-1839-5p and rno-miR-344-3p while OPRL1could be the target of rno-miR-3072 and rno-miR-667-5p (Fig. 6).