Abstract
Papillary thyroid carcinoma (PTC) is one of the most common endocrine system malignancies. However, the mechanism of tumor development is unclear. microRNA-129-5p is a microRNA that plays an important role in the development of tumors. The main purpose of our article is to find the potential target genes of microRNA-129 and their pathways based on gene array, sequencing and bioinformatics studies. We obtained microRNA-129 expression and clinical associations in the TCGA database. In addition, we found a microRNA-129-related chip GSE19933, which is overexpressing microR-129-5p in thyroid cancer cell lines. The down-regulated gene is considered to be a potential target gene for microRNA-129. The target genes were predicted through 12 online tools. We performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of all down-regulated and predicted target genes. Furthermore, protein-protein interactions (PPI) were also analyzed for all potential genes. Finally, with intersecting down-regulated genes by overexpressed microRNA-129 and predicted target genes, the 889 genes are mainly enriched in the calcium signaling pathway, cGMP-PKG signaling pathway, ErbB signaling pathway and Proteoglycans in cancer, etc. The role of ten hub genes is particularly prominent in PPI analysis. These genes are differentially expressed in the thyroid by immunohistochemistry. We confirmed that microRNA-129 may play a major role in PTC through the above pathways, but more experiments are still needed to prove our results.
Keywords: microRNA-129, papillary thyroid carcinoma, TCGA, target gene, signaling pathways
Introduction
Thyroid cancer is a common disease and its diagnosis remains challenging. The symptoms of a palpation, examination by ultrasound, detection of endocrine hormone, fine needle aspiration (FNA) and pathological observation play crucial parts in the diagnosis of thyroid carcinomas. However, the specificity and sensitivity are all required to be improved [1-4]. Papillary thyroid carcinoma (PTC) is the most common cancer originating from the thyroid. Although the prognosis of PTC is commonly good with a high 5-year survival rate, some patients have poorer prognosis. An early diagnosis is of great importance in clinical settings [5-8]. Recently, a class of non-coding single-stranded RNA molecule coded by an endogenous gene, microRNAs (miRNAs) has been reported to be evidently related to the incidence and progress of many cancers, including PTC [9-13]. Hence, miRNAs possess the potential to be trustworthy biomarkers in PTC. However, only a small number of miRNAs have been studied in PTC.
MicroRNA-129 is one of the miRNAs whose clinical role and function remain largely unknown in PTC. To the best of our knowledge, only two research groups have performed relevant studies on microRNA-129 in thyroid cancer. Brest et al. [14] found that histone deacetylase inhibitors (HDACi)s, trichostatin A and vorinostat, could enhance microRNA-129-5p expression in cultured cell lines of BCPAP, TPC-1, 8505C, and CAL62, as well as in primary cultures of PTC cells. Moreover, microRNA-129 was adequate to induce cell death and accentuate the anti-proliferative effects of other cancer drugs. However, no clinical value or molecular target genes of microRNA-129 in PTC were identified in the study [14]. Duan et al. [15] found that microRNA-129-5p was apparently down-regulated in medullary thyroid carcinomas. And microRNA-129-5p could suppress the RET proto-oncogene expression by directly binding its 3’-untranslated regions. However, the study by Duan et al. solely focused on medullary subtype of thyroid carcinoma, without mentioning the more frequent papillary subtype. Besides, only one target gene, RET, was identified.
Therefore, in the present study, the expression level of microRNA-129 was analyzed based on the microRNA sequencing data from the Cancer Genome Atlas (TCGA) Research Network databases, which has recently published a molecular signature based on of 507 PTC and 59 matched non-cancerous adjacent tissues with regard to genomic, transcriptomic and proteomic characteristics, as well as clinicopathological features including survival status [16,17]. Subsequently, the potential target genes of microRNA-129 were gathered by both microarray data and predicting platforms. Finally, a comprehensive functional annotation and validation of the proteins were also performed using different in silico tools.
Materials and methods
Clinical significance of microRNA-129 in papillary thyroid carcinoma based on microRNA sequencing data
The expression levels of microRNA-129-1 and microRNA-129-2, as well as the clinical data of papillary thyroid carcinoma patients and non-tumorous thyroid tissues were provided publically by TCGA data portal (https://gdc-portal.nci.nih.gov/). The expressions of microRNAs were log2 transformed and records were considered as censored when the expression level was less than one. Student’s t test was performed examine the difference of microRNA-129-1 and microRNA-129-2 between cancerous tissues and their non-cancerous counterparts. Receiver operating characteristic (ROC) was drawn to evaluate the diagnostic values of microRNA-129-1 and microRNA-129-2. Kaplan-Meier analysis and univariate Cox proportional hazards regression model were used to assess the prognostic value of microRNA. Overall survival (OS), relapse free survival (RFS) and metastasis free survival data were obtained from PROGmiRV2-Pan Cancer miRNA Prognostics Database (http://xvm145.jefferson.edu/progmir/index.php). SPSS 22.0 (SPSS Inc., Chicago, IL, USA) was used for the statistics and P<0.05 was regarded as being significant.
Potential target genes of microRNA-129
To collect the potential target genes of microRNA-129, we combined two parts of genes together.
The first part was the differentially expressed genes (DEGs) post pre-microRNA-129 overexpression from Gene Expression Omnibus (GEO) database. After searching for “miR-129 OR microRNA-129” in thyroid cancer in GEO, we obtained the database of GSE19933. In the study [14], three independent experiments were performed in dye-swap with TCP1 PTC cells: miRNA-129-5p versus miR-Neg. The experiments included a negative pre-miRNA as control and a synthetic pre-miRNA-129-5p as experimental group. TCP1 papillary thyroid carcinoma cells were transfected with 10 nM of a synthetic pre-miRNA-129-5p or a negative pre-miRNA using Lipofectamine RNAiMAX reagent. RNA samples were harvested at 24 and 48 hours post-transfection. The results of three experiments were merged and the down-expressed genes with a log(FC) value less than -0.5 were gathered as the genes which were directly influenced by microRNA-129 and possessed the potential to be the targets of microRNA-129 in PTC.
The second part was the predicted target genes achieved from 12 different predicting tools, including Targetscan miRWalk, miRMap, Microt4, miRanda, mirbridge, miRDB, miRNAMap, PITA, Pictar2, RNA22, and RNAhybrid. The genes co-predicted by at least six databases were selected.
Finally, the overlapped genes from the two parts were considered as potential target genes of microRNA-129 in PTC.
Functional annotation of the target genes of microRNA-129
To evaluate the function of microRNA-129 target genes in PTC, we analyzed the Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation through DAVID (http://david.abcc.ncifcrf.gov/). The GO terms with a modified Fisher Exact P-value less than 0.01 and the KEGG pathways with P-value less than 0.05 were chosen for next analysis. The GO enrichment analysis was visualized by software Cytoscape v3.5.0. Further, the protein-protein interactions network of genes was conducted through STRING v10.0 (http://string.embl.de/).
Validation of the protein expression level of potential targets
To further confirm the relationship between microRNA-129 and some of the potential target genes. The hub genes from the most significantly enriched pathway in KEGG analysis were selected randomly. We examined the protein expression of these hub genes by Proteinatlas (http://www.proteinatlas.org/). If immunohistochemistry was performed in both non-tumorous tissue and papillary thyroid carcinoma for a certain protein, the immunostaining was presented.
Results
The lowered levels of microRNA-129 in papillary thyroid carcinoma based on microRNA sequencing data
Altogether, there were 507 cases of PTC and 59 non-cancerous thyroid counterparts included in the current study. The level of microRNA-129-1 in papillary thyroid carcinoma tissues was slightly lower than that in non-tumorous tissues. However, the P-value was only 0.082. The AUC also indicated a suboptimal diagnostic value. Regarding microRNA-129-2, a significant lowered level could be observed in the cases of PTC as compared to the counterparts (P=0.049). Furthermore, the AUC was superior to that of microRNA-129-1 (0.588, P=0.027, Figure 1). The interest of the prognostic value of microRNA-129 was also followed subsequently. The K-M curves suggested that the patients with higher microRNA-129-1 and -129-2 levels tended to have a slightly better metastasis free survival (MFS) than those with lower levels, however, the P-value did not reach the significantly statistical standard. Either, no noticeable correlations could be observed between microRNA-129-1 or microRNA-129-2 and OS or RFS (Figures 2, 3 and 4).
Figure 1.

Clinical value of microRNA-129 in papillary thyroid carcinoma based on microRNA sequencing data from TCGA. Expression levels of microRNA-129-1 (A) and microRNA-129-2 (B). Receiver Operating Characteristic (ROCs) curve of microRNA-129-1 (C) and microRNA-129-2 (D). NT: non-tumorous tissue, T: tumor. AUC: area under the ROC curve.
Figure 2.

Correlation between microRNA-129 level and overall survival in papillary thyroid carcinoma based on microRNA sequencing data from TCGA. Expression levels of microRNA-129-1 (A) and microRNA-129-2 (B) were divided according to the median level. The analysis was performed by “PROGmiR” (http://www.compbio.iupui.edu/progmir).
Figure 3.

Correlation between microRNA-129 level and relapse free survival in papillary thyroid carcinoma based on microRNA sequencing data from TCGA. Expression levels of microRNA-129-1 (A) and microRNA-129-2 (B) were divided according to the median level. The analysis was performed by “PROGmiR” (http://www.compbio.iupui.edu/progmir).
Figure 4.

Correlation between microRNA-129 level and metastasis free survival in papillary thyroid carcinoma based on microRNA sequencing data from TCGA. Expression levels of microRNA-129-1 (A) and microRNA-129-2 (B) were divided according to the median level. The analysis was performed by “PROGmiR” (http://www.compbio.iupui.edu/progmir).
Identification of the potential targets of microRNA-129
To further study the potential role of microRNA-129 in PTC, we selected the overlapped genes from two main sources. The dataset GSE19933 represented DEG profiling by microarray post microRNA-129 overexpression, from which we gathered 8378 DEGs after the process described in Materials and Methods. We also obtained 3273 genes as predicted targets of microRNA-129 from at least 6 among 12 predicting platforms. Only genes overlapped by both sources were pooled for next evaluation. Finally, 889 genes were considered as potential targets of microRNA-129 in PTC.
Functional annotation of microRNA-129 target genes
To clarify the function of microRNA-129 in PTC, we conducted gene-annotation enrichment and the KEGG pathway annotation by DAVID. Regarding the biological process in GO analysis, the potential targets of microRNA-129 were significantly involved in the pathways of transcription from RNA polymerase II promoter, negative regulation of cell proliferation, and protein dephosphorylation, etc (Table 1). For cellular component, the genes were most enriched in cytoplasm, nucleus, and nucleoplasm, etc (Table 1). And for molecular function, the selected genes were markedly involved in transcription factor activity, protein binding and sequence-specific DNA binding, etc (Table 1). Regarding the KEGG pathway analysis, the potential targets of microRNA-129 were notably associated with Calcium signaling pathway, cGMP-PKG signaling pathway, ErbB signaling pathway and Proteoglycans in cancer, etc (Table 2). The network analyses of GO-terms and KEGG pathway were visualized by Cytoscape (Figures 5, 6). The protein-protein interaction network analysis was conducted based on the top four pathways from KEGG (Figure 7), which included Calcium signaling pathway, Glioma pathway, Prostate cancer pathway and cGMP-PKG signaling pathway.
Table 1.
GO functional annotation of microRNA-129-5p target genes
| ID | GO Term | Count | P Value | Genes |
|---|---|---|---|---|
| Biological Process | ||||
| GO:0006366 | Transcription from RNA polymerase II promoter | 70 | 1.3E-14 | MEF2C, MEF2A, BACH2, ARID4A, STAT5B, MITF, CCNT1, PAX2, TMF1,etc |
| GO:0045944 | Positive regulation of transcription from RNA polymerase II promoter | 104 | 7.0E-14 | MEF2C, MEF2A, STAT5B, RORA, JAG1, GDNF, IL11, GATA2, MYOCD, etc |
| GO:0045893 | Positive regulation of transcription, DNA-templated | 56 | 3.7E-08 | MEF2C, E2F3, MITF, RORA, PAX2, RFXAP, ZIC2, FUBP3, MYOCD, etc |
| GO:0006351 | Transcription, DNA-templated | 144 | 2.9E-07 | MEF2C, FHIT, MEF2A, JDP2, ZNF451, BBX, CNOT2, ZXDB, RORA, etc |
| GO:0008285 | Negative regulation of cell proliferation | 43 | 1.8E-06 | DLC1, CYP1B1, TFAP4, ERBB4, E2F7, STRN, SOX4, CBFA2T3, MYOCD, etc |
| GO:0006470 | Protein dephosphorylation | 21 | 2.9E-06 | PTPN9, PDP2, PTPN3, SSH1, CDC14B, EPM2A, STYX, SSH2, PTPN14, etc |
| GO:0000122 | Negative regulation of transcription from RNA polymerase II promoter | 63 | 9.0E-06 | MEF2C, JDP2, MEF2A, BACH2, FGF9, E2F7, DICER1, NR6A1, MITF, etc |
| GO:0000186 | Activation of MAPKK activity | 12 | 9.5E-06 | MAP3K7, EGFR, BRAF, ZAK, PLCG1, MAP3K1, KIDINS220, MAP3K13, etc |
| GO:0030279 | Negative regulation of ossification | 7 | 6.9E-05 | MEF2C, NOTCH1, SFRP1, SMAD6, BCL2, CHSY1, SOX9 |
| GO:0000165 | MAPK cascade | 29 | 8.3E-05 | MEF2C, FGFR1, MEF2A, ERBB4, FGF9, GRB2, FGF13, IL17RD, GDNF, etc |
| GO:0035335 | Peptidyl-tyrosine dephosphorylation | 16 | 8.5E-05 | PTPRJ, PTPN9, PTPN3, SSH1, CDC14B, PTPN2, SSH2, PTPN14, DUSP10, etc |
| GO:0006355 | Regulation of transcription, DNA-templated | 105 | 1.5E-04 | MEF2C, FHIT, MEF2A, BBX, CNOT2, ZXDB, HOXD1, RORA, RCBTB1, etc |
| GO:0008284 | Positive regulation of cell proliferation | 42 | 1.9E-04 | FGFR1, E2F3, ERBB4, FGF9, PKHD1, NAP1L1, SOX4, ESM1, SOX9, etc |
| GO:0035019 | Somatic stem cell population maintenance | 12 | 2.8E-04 | ZFP36L2, GATA2, BRAF, SFRP1, EPAS1, SOX2, SMAD4, SOX4, SOX9, etc |
| GO:0007399 | Nervous system development | 29 | 3.8E-04 | MEF2C, ERBB4, FGF13, JAG1, NRN1, GDNF, SEMA5A, PCSK2, ROBO1, etc |
| GO:0001654 | Eye development | 8 | 4.8E-04 | ADAMTS18, ATF6, HMGB1, HIPK1, FGF9, SOX2, SIX3, SIPA1L3 |
| GO:0043410 | Positive regulation of MAPK cascade | 13 | 5.3E-04 | FGFR1, HMGB1, FGF9, SOX2, CDH2, IL6R, KDR, IL11, GRM4, ADRB3, etc |
| GO:0001525 | Angiogenesis | 24 | 5.7E-04 | PIK3CG, FGFR1, EMCN, CYP1B1, EPAS1, FGF9, LEPR, MMP19, RORA, etc |
| GO:0071364 | Cellular response to epidermal growth factor stimulus | 8 | 8.9E-04 | EGFR, ZFP36L2, BAG4, PLCG1, STAT5B, PAX2, SOX9, PTPN12 |
| GO:0001822 | Kidney development | 13 | 9.1E-04 | KIF3A, PKHD1, SOX11, ARID5B, MME, RRM2B, BCL2L11, CDKN1C, etc |
| GO:0010629 | Negative regulation of gene expression | 17 | 1.0E-03 | XDH, PLAG1, MEF2C, STC2, LDLR, RBL2, SOX11, CCR1, NDFIP1, etc |
| GO:0003357 | Noradrenergic neuron differentiation | 4 | 1.1E-03 | PHOX2B, HAND2, SOX11, SOX4 |
| GO:0010468 | Regulation of gene expression | 14 | 1.1E-03 | PHOX2B, DNMT3A, IL7, SOX2, CDK6, FAM46A, GDNF, TAPBP, DDX46, etc |
| GO:0031175 | Neuron projection development | 14 | 1.1E-03 | HMGB1, GNAO1, LYN, VAPA, UBE4B, DOCK7, RB1, GDNF, CAPZB, etc |
| GO:0018108 | Peptidyl-tyrosine phosphorylation | 18 | 1.3E-03 | EGFR, FGFR1, IL3, LYN, ERBB4, FGF9, STAT5B, TTN, EPHB1, KDR, etc |
| GO:0043066 | Negative regulation of apoptotic process | 38 | 1.6E-03 | ERBB4, PKHD1, STAT5B, SOX9, PAX2, GDNF, TMF1, PHIP, IGF1R, etc |
| GO:0060314 | Regulation of ryanodine-sensitive calcium-release channel activity | 6 | 1.8E-03 | JPH4, NOS1, PLN, CAMK2D, PDE4D, CALM1 |
| GO:0046777 | Protein autophosphorylation | 19 | 1.9E-03 | EGFR, FGFR1, LYN, ERBB4, MAK, TAOK3, STK17B, SMG1, PRKX, etc |
| GO:0007601 | Visual perception | 21 | 2.0E-03 | MYO5A, OPA3, CYP1B1, IRX5, EPAS1, PITPNA, SIX3, KCNJ10, PAX2, etc |
| GO:0071560 | Cellular response to transforming growth factor beta stimulus | 9 | 2.3E-03 | MEF2C, ZFP36L2, SFRP1, FYN, PDE3A, XCL1, YES1, SOX9, WWOX |
| GO:0071456 | Cellular response to hypoxia | 13 | 2.4E-03 | DNMT3A, ACAA2, KCND2, EPAS1, STC2, RORA, SLC2A4, SFRP1, GNB1, etc |
| GO:0007169 | Transmembrane receptor protein tyrosine kinase signaling pathway | 13 | 2.4E-03 | EGFR, MPZL1, LYN, ERBB4, PTPRT, KDR, IGF1R, FYN, ROR1, JAK1, etc |
| GO:0045668 | Negative regulation of osteoblast differentiation | 8 | 2.5E-03 | TWSG1, HDAC4, NOTCH1, SFRP1, HAND2, CDK6, TOB1, IGFBP5 |
| GO:0007223 | Wnt signaling pathway, calcium modulating pathway | 8 | 2.5E-03 | MAP3K7, GNAO1, GNB1, GNG2, FZD3, PPP3CA, CAMK2A, CALM1 |
| GO:0045892 | Negative regulation of transcription, DNA-templated | 40 | 2.5E-03 | ARID4A, TFAP4, PAX2, SOX9, CBFA2T3, CBFA2T2, ZIC2, MINA, etc |
| GO:0043547 | Positive regulation of GTPase activity | 44 | 2.5E-03 | DLC1, ALS2, SNX9, FGFR1, ERBB4, GRB2, FGF9, MYO9B, MYO9A, etc |
| GO:0048706 | Embryonic skeletal system development | 7 | 2.9E-03 | HOXC6, SLC35D1, FGF9, SP3, HOXB9, HOXD1, PCSK5 |
| GO:0038083 | Peptidyl-tyrosine autophosphorylation | 8 | 2.9E-03 | IGF1R, ERBB4, LYN, FYN, JAK1, YES1, ABL2, KDR |
| GO:0006357 | Regulation of transcription from RNA polymerase II promoter | 36 | 3.2E-03 | GLIS3, HMGB1, JDP2, SOX21, ARID4A, KIAA1958, MITF, ARID4B, etc |
| GO:0048839 | Inner ear development | 8 | 3.3E-03 | MAF, PHOX2B, CDKN1B, FREM2, SOX2, PDGFRB, SLC25A27, PTPN11 |
| GO:0060045 | Positive regulation of cardiac muscle cell proliferation | 6 | 3.6E-03 | MEF2C, FGFR1, NOTCH1, ERBB4, FGF9, FGF2 |
| GO:0060021 | Palate development | 11 | 3.7E-03 | MEF2C, CHD7, MSX1, HAND2, BNC2, ARID5B, FOXF2, GDF11, SMAD4, etc |
| GO:0010001 | Glial cell differentiation | 5 | 3.8E-03 | PHOX2B, CDH2, PAX2, FGF2, NFIB |
| GO:0001658 | Branching involved in ureteric bud morphogenesis | 8 | 3.8E-03 | LHX1, BCL2, SMAD4, WNT9B, PAX2, SOX9, GDNF, FGF2 |
| GO:0010976 | Positive regulation of neuron projection development | 12 | 3.9E-03 | FGFR1, LYN, FYN, AVIL, PRKCI, PTN, NFE2L2, KIDINS220, etc |
| GO:0030155 | Regulation of cell adhesion | 8 | 4.4E-03 | PTPRJ, EMCN, ROCK1, EPHA8, PPP1R12A, SOX9, ABL2, PRKX |
| GO:0048485 | Sympathetic nervous system development | 5 | 5.0E-03 | PHOX2B, HAND2, SOX11, SOX4, GDNF |
| GO:0046928 | Regulation of neurotransmitter secretion | 5 | 5.0E-03 | CPLX4, MEF2C, FMR1, RIMS1, CAMK2A |
| GO:0060397 | JAK-STAT cascade involved in growth hormone signaling pathway | 5 | 5.0E-03 | LYN, STAT5B, PTPN1, STAT3, GHR |
| GO:0046903 | Secretion | 4 | 5.4E-03 | NPY2R, PRKCI, TPD52, RIMS1 |
| GO:1903358 | Regulation of Golgi organization | 4 | 5.4E-03 | MYO5A, STX18, RAB33B, USP6NL |
| GO:0007173 | Epidermal growth factor receptor signaling pathway | 9 | 5.5E-03 | EGFR, CBLB, CAMLG, PLCG1, GRB2, TGFA, SOCS5, SOX9, PTPN11 |
| GO:0046854 | Phosphatidylinositol phosphorylation | 12 | 5.9E-03 | PIK3CG, EGFR, FGFR1, ERBB4, FYN, GRB2, FGF9, PDGFRB, SMG1, etc |
| GO:0008584 | Male gonad development | 12 | 5.9E-03 | NCOA1, TNFSF10, SFRP1, FGF9, BCL2, ARID5B, GATA4, RNF38, etc |
| GO:0060216 | Definitive hemopoiesis | 5 | 6.4E-03 | TAL1, ZFP36L2, GATA2, HIPK1, SP3 |
| GO:0030900 | Forebrain development | 8 | 6.5E-03 | DLC1, TWSG1, NOTCH1, SSTR2, GNAO1, FYN, SOX2, FRS2 |
| GO:0007267 | Cell-cell signaling | 23 | 6.6E-03 | IL3, MPZL1, FGF9, IL7, GRB2, CCR1, PCDH8, FGF13, IL11, GJA3, etc |
| GO:0017148 | Negative regulation of translation | 9 | 6.8E-03 | TIA1, FMR1, CNOT2, SYNCRIP, FXR2, TOB1, PURA, IGFBP5, FXR1 |
| GO:0001501 | Skeletal system development | 15 | 7.0E-03 | HAPLN1, FGFR1, SOX11, SOX4, MEPE, SOX9, ANKH, HOXC10, CDKN1C, etc |
| GO:0071407 | Cellular response to organic cyclic compound | 9 | 7.5E-03 | CDKN1B, CYP1B1, ITGA6, PAK2, PAK3, SMAD5, STAT3, TMF1, IGFBP5 |
| GO:0010863 | Positive regulation of phospholipase C activity | 4 | 7.8E-03 | FGFR1, PDGFRB, ABL2, FGF2 |
| GO:2000737 | Negative regulation of stem cell differentiation | 4 | 7.8E-03 | ZFP36L2, NOTCH1, JAG1, STAT3 |
| GO:0050679 | Positive regulation of epithelial cell proliferation | 9 | 8.3E-03 | EGFR, NOTCH1, KIF3A, SFRP1, FGF9, TGFA, PAX2, SOX9, FOXP1 |
| GO:0072332 | Intrinsic apoptotic signaling pathway by p53 class mediator | 6 | 8.9E-03 | FHIT, E2F2, TP53BP2, EDA2R, PERP, WWOX |
| GO:0030522 | Intracellular receptor signaling pathway | 7 | 9.5E-03 | NOTCH2, NCOA1, NR4A2, RORA, HNF4G, STAT3, ARNT |
| Cellular Component | ||||
| GO:0005737 | Cytoplasm | 314 | 3.3E-08 | MEF2C, DLC1, FHIT, MEF2A, PITPNA, DZIP1, STAT5B, BBX, AQP4, etc |
| GO:0005634 | Nucleus | 319 | 2.0E-07 | MEF2C, DLC1, FHIT, MEF2A, DZIP1, STAT5B, SYNCRIP, RORA, RFXAP, etc |
| GO:0005654 | Nucleoplasm | 182 | 6.2E-07 | MEF2C, MEF2A, DZIP1, STAT5B, IDE, BBX, SYNCRIP, RORA, IL17RD, etc |
| GO:0005667 | Transcription factor complex | 24 | 3.1E-05 | E2F2, E2F3, MEF2A, EPAS1, RBL2, SMAD6, E2F7, SMAD5, SOX2, etc |
| GO:0043005 | Neuron projection | 25 | 2.7E-04 | MYO5A, HMGB1, SLC6A2, FGF13, CXADR, HNMT, ANK3, BCL11B, AVIL, etc |
| GO:0005794 | Golgi apparatus | 63 | 3.8E-04 | IER3IP1, SYT4, LDLR, PAX2, IL17RD, SLC35A3, SPRY4, TMF1, etc |
| GO:0043235 | Receptor complex | 16 | 7.8E-04 | EGFR, FGFR1, OLR1, ERBB4, LDLR, LEPR, LRP1B, PEX5L, ITPR2, etc |
| GO:0017053 | Transcriptional repressor complex | 10 | 8.7E-04 | HMGB1, HDAC4, CTBP2, TFAP4, ARID4A, SP3, JAZF1, HDGF, YWHAB, PHF12 |
| GO:0005886 | Plasma membrane | 228 | 1.5E-03 | VAPA, SYT4, AQP4, MAP3K7, ATP2B3, GRIN2D, RAPGEF4, GNG2, etc |
| GO:0005829 | Cytosol | 186 | 2.7E-03 | ALS2, DLC1, MEF2C, FHIT, STAT5B, EIF5, IDE, STYX, CNOT2, TTN, etc |
| GO:0030425 | Dendrite | 28 | 3.8E-03 | GNAZ, ALS2, SYT4, DICER1, KCNA1, MME, FGF13, EPHB1, ALCAM, etc |
| GO:0005768 | Endosome | 21 | 4.0E-03 | EGFR, HMGB1, SNX9, LEPROTL1, LDLR, GRB2, RAB4A, MYO1D, PRKCI, etc |
| GO:0016323 | Basolateral plasma membrane | 18 | 4.2E-03 | EGFR, MPZ, ERBB4, LDLR, LEPR, MYO1D, AQP4, KCNJ10, IL6R, etc |
| GO:0016529 | Sarcoplasmic reticulum | 7 | 4.3E-03 | XDH, ANK1, NOS1, ATP2A2, ANK3, MRVI1, CAMK2D |
| GO:0045202 | Synapse | 18 | 4.4E-03 | CPLX4, EGFR, NMNAT2, FLRT2, NOS1, FMR1, KCNA1, DLGAP4, MME, etc |
| GO:0030054 | Cell junction | 35 | 4.8E-03 | CPLX4, SYT4, KCNA1, NRN1, CXADR, RIMS1, AMPH, GRIN2D, GOPC, etc |
| GO:0044853 | Plasma membrane raft | 4 | 6.7E-03 | PRKAR2A, KCND2, MYO1D, CDH2 |
| GO:0043234 | Protein complex | 31 | 9.7E-03 | MEF2C, ALS2, DZIP1, MITF, NR3C1, SOX9, PAX2, CXADR, HAND2, etc |
| Molecular Function | ||||
| GO:0001077 | Transcriptional activator activity, RNA polymerase II core promoter proximal region sequence-specific binding | 43 | 1.9E-13 | MEF2C, CAMTA1, MEF2A, TFAP4, STAT5B, NR6A1, SOX2, MITF, SOX4, etc |
| GO:0003700 | Transcription factor activity, sequence-specific DNA binding | 100 | 5.2E-13 | MEF2C, MEF2A, JDP2, ZNF451, STAT5B, RORA, RFXAP, ZIC2, HOXC6, etc |
| GO:0005515 | Protein binding | 504 | 1.5E-08 | MEF2C, DLC1, ALS2, FHIT, MEF2A, LTBP2, SYNCRIP, STRN, RORA, etc |
| GO:0043565 | Sequence-specific DNA binding | 54 | 2.2E-07 | JDP2, MEF2A, NR6A1, RORA, HOXD1, HOXC6, HOXC9, GATA4, FOXF2, etc |
| GO:0000978 | RNA polymerase II core promoter proximal region sequence-specific DNA binding | 42 | 2.3E-07 | MEF2C, JDP2, MEF2A, TFAP4, NR6A1, MITF, CTCFL, NR3C1, MYBL1, etc |
| GO:0000977 | RNA polymerase II regulatory region sequence-specific DNA binding | 30 | 2.9E-07 | MEF2C, MEF2A, E2F7, RORA, TAL1, GATA2, HAND2, GATA4, FOXF2, etc |
| GO:0005088 | Ras guanyl-nucleotide exchange factor activity | 20 | 2.5E-06 | EGFR, FGFR1, IL3, ERBB4, FGF9, GRB2, GDNF, ADRB1, RASGRF2, etc |
| GO:0004725 | Protein tyrosine phosphatase activity | 18 | 5.7E-06 | PTPRJ, PTPN9, PTPN3, SSH1, CDC14B, PTPN2, EPM2A, SSH2, PTPN14, etc |
| GO:0003677 | DNA binding | 119 | 1.7E-05 | MEF2C, MEF2A, BBX, RORA, RFXAP, ZIC2, HOXC6, GATA4, FOXF2, etc |
| GO:0044212 | Transcription regulatory region DNA binding | 25 | 1.1E-04 | MEF2C, ARID4A, ERBB4, TFAP4, SMAD6, ARID5B, CCNT1, SOX2, etc |
| GO:0004713 | Protein tyrosine kinase activity | 18 | 2.4E-04 | EGFR, FGFR1, IL3, LYN, ERBB4, FGF9, STAT5B, TTN, KDR, IGF1R, etc |
| GO:0001105 | RNA polymerase II transcription coactivator activity | 9 | 3.2E-04 | MEF2A, NCOA1, MYOCD, SOX11, PYGO2, SOX4, POU3F2, ISL1, WWOX |
| GO:0003682 | Chromatin binding | 36 | 3.6E-04 | MEF2C, JDP2, MEF2A, CCNT1, STAT5B, SOX9, TAL1, GATA2, CHD7, etc |
| GO:0019899 | Enzyme binding | 32 | 4.0E-04 | HLCS, TTN, TAL1, DAOA, GSTM3, ANK1, PPP1R3B, CNTNAP2, HSPA5, etc |
| GO:0046934 | Phosphatidylinositol-4,5-bisphosphate 3-kinase activity | 11 | 7.4E-04 | PIK3CG, EGFR, FGFR1, ERBB4, FYN, GRB2, FGF9, PDGFRB, FGF2, etc |
| GO:0042803 | Protein homodimerization activity | 56 | 7.7E-04 | ALS2, SEPHS1, IDE, NR6A1, HLCS, TPD52, GDNF, GSTM3, BHLHB9, etc |
| GO:0005516 | Calmodulin binding | 21 | 8.7E-04 | MYO5A, EGFR, NOS1, PHKG2, MYO1D, STRN, EEA1, MYO9B, TTN, etc |
| GO:0044325 | Ion channel binding | 15 | 1.1E-03 | NOS1, LYN, KCNAB1, FMR1, FGF13, PDE4D, RIMS1, PPP1R9A, YWHAH, etc |
| GO:0046982 | Protein heterodimerization activity | 38 | 2.2E-03 | MEF2C, MEF2A, JDP2, SEPHS1, TFAP4, VAPA, SOX4, TPD52, RRAGD, etc |
| GO:0001158 | Enhancer sequence-specific DNA binding | 6 | 2.2E-03 | GATA2, SOX11, GATA4, ZNF395, ISL1, SOX9 |
| GO:0005545 | 1-phosphatidylinositol binding | 6 | 2.2E-03 | WDFY3, SNX9, WDFY1, SESTD1, EEA1, SNX10 |
| GO:0001222 | Transcription corepressor binding | 4 | 3.4E-03 | SIX3, HDGF, PHF12, RORA |
| GO:0004709 | MAP kinase activity | 6 | 3.5E-03 | MAP3K7, EGFR, BRAF, ZAK, MAP3K1, MAP3K13 |
| GO:0033613 | Activating transcription factor binding | 6 | 3.5E-03 | MEF2C, MEF2D, HDAC4, MEF2A, HAND2, GATA4 |
| GO:0001047 | Core promoter binding | 10 | 3.5E-03 | E2F2, HDAC4, NOTCH1, E2F3, MTF1, ELK4, E2F7, TFAP2C, RB1, CLOCK |
| GO:0042826 | Histone deacetylase binding | 13 | 3.8E-03 | MEF2C, MEF2A, TFAP4, YWHAB, PKN2, SIX3, HDAC4, MEF2D, TAL1, etc |
| GO:0000981 | RNA polymerase II transcription factor activity, sequence-specific DNA binding | 18 | 4.0E-03 | MEF2C, MEF2A, SOX21, EPAS1, KIAA1958, SIX3, FOXJ3, SOX9, etc |
| GO:0030971 | Receptor tyrosine kinase binding | 8 | 4.3E-03 | CBLB, PLCG1, PTPN2, PTPN14, PTPN1, SOCS5, TOB1, PTPN11 |
| GO:0003705 | Transcription factor activity, RNA polymerase II distal enhancer sequence-specific binding | 10 | 4.4E-03 | MEF2A, PKNOX1, TFAP4, FOXF2, RFX3, OLIG2, SOX9, FOXP1, ARNT, PURA |
| GO:0005178 | Integrin binding | 13 | 4.8E-03 | EGFR, LYN, ADAM23, PTPN2, EDIL3, ESM1, CXADR, ECM2, COL5A1, etc |
| GO:0004726 | Non-membrane spanning protein tyrosine phosphatase activity | 4 | 5.3E-03 | PTPN9, PTPN2, PTPN12, PTPN11 |
| GO:0004721 | Phosphoprotein phosphatase activity | 8 | 5.5E-03 | PPP1R3B, SSH1, PPP2CB, SSH2, DUSP10, PPP3CA, PTPN12, PTPN11 |
| GO:0008134 | Transcription factor binding | 25 | 6.0E-03 | E2F2, HMGB1, SP100, EPAS1, CCNT1, KEAP1, RB1, RORA, PAX2, etc |
| GO:0001228 | Transcriptional activator activity, RNA polymerase II transcription regulatory region Sequence-specific binding | 12 | 6.2E-03 | MAF, GATA2, MSX1, PKNOX1, MYOCD, FOXF2, GATA4, ESRRG, SMAD4, etc |
| GO:0046872 | Metal ion binding | 124 | 8.8E-03 | MKRN1, PDP2, SYT4, SLC6A2, DZIP1, ZNF451, IDE, ZXDB, ZIC2, etc |
| GO:0003713 | Transcription coactivator activity | 22 | 9.4E-03 | SP100, CTBP2, TFAP4, UBE3A, MAK, TAF4B, ARID5B, SIX3, RB1, etc |
Note: GO, Gene Ontology.
Table 2.
KEGG pathway enriched by microRNA-129-5p target genes
| ID | GO Term | Count | P Value | Genes |
|---|---|---|---|---|
| hsa04020 | Calcium signaling pathway | 28 | 1.2E-06 | ERBB4, PPP3R2, ADRB3, HRH1, ATP2B3, GRIN2D, CAMK2D, PPP3CA, etc |
| hsa05214 | Glioma | 16 | 1.4E-06 | PIK3CG, EGFR, E2F2, E2F3, BRAF, GRB2, CDK6, RB1, IGF1R, PLCG1, etc |
| hsa05215 | Prostate cancer | 17 | 1.7E-05 | PIK3CG, EGFR, FGFR1, E2F2, E2F3, BRAF, GRB2, CREB5, RB1, etc |
| hsa04022 | cGMP-PKG signaling pathway | 24 | 3.0E-05 | MEF2C, PIK3CG, MEF2A, ROCK1, MRVI1, PPP3R2, PDE3A, CREB5, etc |
| hsa04012 | ErbB signaling pathway | 16 | 6.1E-05 | PIK3CG, EGFR, ERBB4, BRAF, GRB2, STAT5B, CBLB, CDKN1B, PAK2, etc |
| hsa05205 | Proteoglycans in cancer | 26 | 7.9E-05 | FGFR1, ERBB4, TFAP4, GRB2, SDC2, IGF1R, ANK1, ANK3, SOS2, etc |
| hsa05200 | Pathways in cancer | 41 | 8.1E-05 | E2F2, FGFR1, E2F3, GRB2, FGF9, STAT5B, MITF, FGF13, CXCL12, etc |
| hsa05218 | Melanoma | 14 | 1.0E-04 | PIK3CG, EGFR, FGFR1, E2F2, E2F3, BRAF, FGF9, MITF, CDK6, etc |
| hsa05161 | Hepatitis B | 21 | 1.1E-04 | PIK3CG, E2F2, EGR3, E2F3, GRB2, STAT5B, SMAD4, YWHAB, CDK6, etc |
| hsa05220 | Chronic myeloid leukemia | 14 | 1.2E-04 | PIK3CG, E2F2, E2F3, CBLB, CDKN1B, CTBP2, BRAF, GRB2, SOS2, etc |
| hsa05223 | Non-small cell lung cancer | 12 | 1.8E-04 | PIK3CG, EGFR, FHIT, E2F2, E2F3, BRAF, PLCG1, GRB2, SOS2, etc |
| hsa04151 | PI3K-Akt signaling pathway | 36 | 2.5E-04 | FGFR1, FGF9, GRB2, FGF13, IGF1R, BCL2, PPP2CB, SOS2, CREB3L2, etc |
| hsa04024 | cAMP signaling pathway | 24 | 4.5E-04 | PIK3CG, PTGER3, ROCK1, BRAF, PDE3A, CREB5, PDE4D, GRIA4, etc |
| hsa04360 | Axon guidance | 18 | 5.0E-04 | LRRC4, ROCK1, PLXNA2, DPYSL5, PPP3R2, CXCL12, EPHB1, SLIT3, etc |
| hsa05212 | Pancreatic cancer | 12 | 6.9E-04 | PIK3CG, EGFR, E2F2, E2F3, BRAF, SMAD4, TGFA, BRCA2, JAK1, etc |
| hsa04725 | Cholinergic synapse | 16 | 9.5E-04 | PIK3CG, GNAO1, CREB5, ITPR2, KCNQ5, GNB1, FYN, CHRM1, BCL2, etc |
| hsa04728 | Dopaminergic synapse | 17 | 1.5E-03 | GNAO1, CREB5, GRIA4, ITPR2, GNAL, GNB1, PPP2CB, CAMK2D, etc |
| hsa04066 | HIF-1 signaling pathway | 14 | 2.4E-03 | EGFR, PIK3CG, IGF1R, CYBB, CDKN1B, PLCG1, BCL2, CAMK2D, HK2, etc |
| hsa05211 | Renal cell carcinoma | 11 | 2.5E-03 | PIK3CG, BRAF, PAK2, EPAS1, PAK3, GRB2, SOS2, TGFA, TCEB1, etc |
| hsa04010 | MAPK signaling pathway | 26 | 3.0E-03 | MEF2C, FGFR1, ZAK, FGF9, GRB2, CACNB1, DUSP10, PPP3R2, FGF13, etc |
| hsa04014 | Ras signaling pathway | 23 | 5.7E-03 | PIK3CG, EGFR, FGFR1, GRB2, FGF9, FGF13, KDR, PTPN11, IGF1R, etc |
| hsa04915 | Estrogen signaling pathway | 13 | 7.3E-03 | EGFR, PIK3CG, GNAO1, SP1, FKBP5, GRB2, SOS2, CREB3L2, etc |
| hsa05203 | Viral carcinogenesis | 21 | 8.0E-03 | PIK3CG, EGR3, SP100, RBL2, LYN, UBE3A, GRB2, STAT5B, YWHAB, etc |
| hsa05031 | Amphetamine addiction | 10 | 9.1E-03 | GRIN2D, CREB3L2, CAMK2D, PPP3R2, CREB3L1, CREB5, GRIA4, etc |
| hsa04660 | T cell receptor signaling pathway | 13 | 9.9E-03 | PIK3CG, GRB2, PPP3R2, MAP3K7, CBLB, PLCG1, PAK2, FYN, PAK3, etc |
| hsa04921 | Oxytocin signaling pathway | 17 | 1.2E-02 | PIK3CG, EGFR, MEF2C, GNAO1, ROCK1, CACNB1, PPP3R2, ITPR2, etc |
| hsa04261 | Adrenergic signaling in cardiomyocytes | 16 | 1.3E-02 | PIK3CG, MYL3, CACNB1, CREB5, TPM3, ATP2B3, ADRB1, PLN, BCL2, etc |
| hsa04520 | Adherens junction | 10 | 1.4E-02 | MAP3K7, PTPRJ, EGFR, IGF1R, FGFR1, SORBS1, FYN, SMAD4, PTPN1, YES1 |
| hsa04730 | Long-term depression | 9 | 1.5E-02 | GNAZ, IGF1R, GNAO1, NOS1, BRAF, LYN, PPP2CB, GRM1, ITPR2 |
| hsa04550 | Signaling pathways regulating pluripotency of stem cells | 15 | 2.0E-02 | PIK3CG, FGFR1, GRB2, SMAD5, SOX2, SMAD4, FZD3, ISL1, STAT3, etc |
| hsa04724 | Glutamatergic synapse | 13 | 2.1E-02 | GNAO1, PPP3R2, GRIA4, SHANK2, GRM1, ITPR2, GRM4, GRM8, GNB1, etc |
| hsa04810 | Regulation of actin cytoskeleton | 20 | 2.1E-02 | PIK3CG, EGFR, FGFR1, ROCK1, SSH1, BRAF, FGF9, SSH2, FGF13, etc |
| hsa04720 | Long-term potentiation | 9 | 2.6E-02 | BRAF, GRIN2D, CAMK2D, PPP3R2, PPP3CA, GRM1, CAMK2A, ITPR2, CALM1 |
| hsa04722 | Neurotrophin signaling pathway | 13 | 3.0E-02 | PIK3CG, PLCG1, BRAF, GRB2, BCL2, MAP3K1, SOS2, CAMK2D, etc |
| hsa04068 | FoxO signaling pathway | 14 | 3.1E-02 | PIK3CG, EGFR, BRAF, RBL2, GRB2, SMAD4, GRM1, BCL2L11, STAT3, etc |
| hsa04925 | Aldosterone synthesis and secretion | 10 | 3.1E-02 | LDLR, CREB3L2, CAMK2D, NR4A2, CREB3L1, CREB5, CAMK2A, CAMK1D, etc |
| hsa04662 | B cell receptor signaling pathway | 9 | 3.3E-02 | PIK3CG, LYN, DAPP1, GRB2, SOS2, PPP3R2, PPP3CA, NFATC2, NFATC3 |
| hsa04015 | Rap1 signaling pathway | 19 | 3.7E-02 | PIK3CG, EGFR, FGFR1, GNAO1, BRAF, FGF9, PRKCI, SIPA1L3, etc |
| hsa04910 | Insulin signaling pathway | 14 | 3.8E-02 | PIK3CG, BRAF, GRB2, PHKG2, HK2, PRKCI, PRKAR2A, CBLB, etc |
| hsa04350 | TGF-beta signaling pathway | 10 | 3.9E-02 | INHBB, ROCK1, SP1, SMAD6, PPP2CB, SMAD5, FST, INHBC, SMAD4, TGIF2 |
| hsa04723 | Retrograde endocannabinoid signaling | 11 | 4.8E-02 | GNAO1, GABRA4, GNB1, GABRA3, GNG2, GRIA4, GRM1, RIMS1, GNG7, etc |
Note: KEGG, Kyoto Encyclopedia of Genes and Genomes.
Figure 5.

GO-terms network analysis enriched by microRNA-129 target genes. The analysis was visualized by Cytoscape. The color of lines represents the degree of fold enrichment, and the color of circles represents the enriched number of genes.
Figure 6.

KEGG pathway network analysis enriched by microRNA-129 target genes. The analysis was visualized by Cytoscape. The color of lines represents the degree of fold enrichment, and the color of circles represents the enriched number of genes.
Figure 7.
Interaction network analysis of genes from top four KEGG pathways. A. Calcium signaling pathway. B. Glioma. C. Prostate cancer. D. cGMP-PKG signaling pathway.
Validation of the potential targets from calcium signaling pathway
To validate the relationship between microRNA-129 and some of the potential target genes. We examined the protein expression of the 10 hub genes randomly selected from Calcium signaling pathway, which was demonstrated as the most significantly enriched pathway in KEGG analysis and was also confirmed to play essential role in the tumorigenesis and development of PTC [18-25]. The Human Protein Atlas showed that prominently higher expression of ERBB4, PDGFRB, PLCG1, PPP3CA, PPP3R2, CALM1, CAMK2A, CAMK2D and EGFR could be observed (Figures 8, 9), which supported the hypothesis that these genes could be the real targets of microRNA-129 in PTC. GRIN2D protein expression data was not provided by Proteinatlas.
Figure 8.

Protein expression of hub genes in papillary thyroid carcinoma. NT, normal tissue; PTC, papillary thyroid carcinoma. The immunohistochemical staining of potential targets of microRNA-129-5p were provided by The Human Protein Atlas. A: Erb-b2 receptor tyrosine kinase 4 (ERBB4). B: Patelet-derived growth factor receptor, beta polypeptide (PDGFRB). C: Phospholipase C, gamma 1 (PLCG1). D: Protein phosphatase 3, catalytic subunit, alpha isozyme (PPP3CA). E: Protein phosphatase 3, regulatory subunit B, beta (PPP3R2).
Figure 9.

Protein expression of hub genes in papillary thyroid carcinoma. NT, normal tissue; PTC, papillary thyroid carcinoma. The immunohistochemical staining of potential targets of microRNA-129-5p were provided by The Human Protein Atlas. A: Calmodulin 1 (phosphorylase kinase, delta) (CALM1). B: Calcium/calmodulin-dependent protein kinase II alpha (CAMK2A). C: Calcium/calmodulin-dependent protein kinase II delta (CAMK2D). D: Epidermal growth factor receptor (EGFR).
Discussion
In the present study, the significant lowered expression level of microRNA-129 in PTC was observed based on the microRNA sequencing data from TCGA with 507 patients. The potential target genes were enriched in various signaling pathways, especially calcium signaling pathway from KEGG analysis. Furthermore, nine targets, namely ERBB4, PDGFRB, PLCG1, PPP3CA, PPP3R2, CALM1, CAMK2A, CAMK2D and EGFR were randomly selected from calcium signaling pathway for the protein validation. All the nine genes were markedly overexpressed in PTC tissues based on Proteinatlas data with tissue array and immunohistochemistry. The results of current study provide new insight for the future clinical application of microRNA-129 in PTC. However, the exact molecular mechanism of microRNA-129 in PTC needs further investigation.
There is an increasing knowledge that identifies the significance of microRNA-129 during the progress of various cancers, including prostate cancer, gastric cancer, breast cancer, hepatocellular carcinoma, and glioblastoma, etc [26-38]. However, the clinical role and function of microRNA-129 remained largely unclarified in thyroid cancer. By far, only two groups performed relevant study on microRNA-129 in thyroid cancers. Brest et al. [14] found that microRNA-129-5p was obligatory for histone deacetylase inhibitor-induced cell death in thyroid cancer cells, but no clinical role and target genes were identified. Duan et al. [15] reported that microRNA-129-5p expression was remarkably lowered in medullary thyroid carcinomas, without investigating other subtypes of thyroid cancers. In the current study, we found the microRNA-129-2 was apparently down-regulated in PTC tissues, similar but not significant down-regulation was also observed with microRNA-129-1. These patterns suggested that microRNA-129 might be a suppressive microRNA in thyroid carcinoma. In the survival analysis, no significant relationship was obtained between either microRNA-129-1 or microRNA-129-2 and different prognostic parameters, including OS, RFS or MFS. However, the aforementioned data were based on a single detecting method, microRNA sequencing. The exact diagnostic and prognostic values of microRNA-129 need to be validated with other approaches, such as real time RT-qPCR or FISH, with other independent cohort.
As for the function and molecular mechanism of microRNA-129 in PTC, no study has been performed so far. Duan et al. [15] found that microRNA-129-5p could target and suppress REarranged during Transfection proto-oncogene (RET) expression. Ectopic expression of microRNA-129-5p reduced cell growth, induced apoptosis and inhibited migration capability in medullary thyroid carcinomas cells via reducing the phosphorylated level of AKT.
Mature miRNA participates in the construction of RNA-induced silencing complex, identified as the miRNA ribonucleoprotein complex. In most of the circumstances, single-stranded miRNA of compounds and 3’-UTR of its homologous mRNA share imperfect complementary pairing bases, which will thus disturb the translation of the gene and modulate the following protein expression. In some other cases, miRNA and its target mRNAs share thorough complementation, which will cause a particular degradation of target mRNA in the complementary region and finally lead to gene silencing [39,40]. This characteristics of miRNA assists the development of various predicting programs for the potential target genes of miRNAs.
The existing methodologies of miRNA target gene prediction via in silico inquiry are manufactured upon sequence similarity search and thermodynamic stability. However, it is known that the results of in silico target prediction algorithms undergo limited specificity. Hence, the combination of in silico target predictions with gene expression profiling has been demonstrated to be able to increase the identification of functional miRNA-target gene relationships. After receiving such inspiration, we combined the predicting target genes from at least 6 platforms and the DEGs post microRNA-129 transfection in vitro. The eventual 889 genes were achieved, which we believed to have high possibilities to be the real targets of microRNA-129 in PTC. To test this hypothesis, we randomly took 10 hub genes from the calcium signaling pathway for validation. Only the protein level of GRIN2D was absent in Proteinatlas. Importantly, the leaving nine genes all showed consistently higher expression level in PTC, which suggested that they had more likelihoods to be targeted by microRNA-129, as it is lowered expressed in PTC, including ERBB4, PPP3R2, PPP3CA, CAMK2D, CAMK2A, CALM1, PLCG1, PDGFRB and EGFR. However, other in-depth in vitro experiments need to be carried out to unveil the miRNA-target relationships.
Collectively, the notably lowered expression level of microRNA-129 in PTC could play a pivotal role in the tumorigenesis of PTC. The biological function of microRNA-129 might be carried out via target multiple signaling pathways, among which, calcium signaling pathway from KEGG analysis is the most significant one. Nine targets, including ERBB4, PPP3R2, PPP3CA, CAMK2D, CAMK2A, CALM1, PLCG1, EGFR and PDGFRB, could be real target of microRNA-129 in PTC. However, the clinical role and exact molecular mechanism of microRNA-129 in PTC needs further exploration.
Acknowledgements
The authors thank TCGA and Protein atlas for providing the data. The study is funded by Guangxi Scientific Research and Technology Development Plan (1598011-4), the National Natural Science Foundation of China (81560448), and Guangxi Health Bureau Research Project (Z2012053).
Disclosure of conflict of interest
None.
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