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MicroRNA-seq of cartilage reveals an over-abundance of miR-140-3p which contains functional isomiRs (Illumina HT12v4 expression arrays)

ABSTRACT: MiR-140 is selectively expressed in cartilage. Deletion of the entire miR-140 locus in mice results in a growth retardation phenotype and an early-onset osteoarthritis-like pathology, however the relative contribution of miR-140-5p or miR-140-3p to the phenotype remains to be determined. An unbiased small RNA sequencing approach identified that miR-140-3p was in vast abundance (>10-fold) to miR-140-5p in human cartilage. Analysis of these data identified multiple miR-140-3p isomiRs differing from the miRBase [1] annotation at both the 5´ and 3´ end, with >99% of miR-140-3p isomiRs having one of two ‘seed’ sequences (5´ bases 2-8). The most abundant isomiR with each seed were selected for further analysis; miR-140-3p.2 which has an identical seed to the miRBase miR-140-3p (ACCACAG) and miR-140-3p.1 which has an altered seed (CCACAGG), and thus different potential targets. Each isomiR was overexpressed in chondrocytes and whole-genome transcriptomics used to identify targets. miR-140-3p.1 and miR-140-3p.2 significantly down-regulated 694 and 238 genes respectively (adj.P.Val<0.05), of which only 162 genes were commonly down-regulated by both isomiRs. Targets of both isomiRs were validated using 3´UTR luciferase assays. A significant enrichment of miR-140-3p.1 targets was identified within genes whose expression increase in the rib chondrocytes of Mir140-null mice and within genes whose expression decreased during human chondrogenesis. Finally, through imputing the expression of miR-140 from the expression of the host gene WWP2 in 124 previously published datasets an inverse correlation with miR-140-3p.1 predicted targets was identified. Together these data suggest the novel seed containing isomiR miR-140-3p.1 is more functional than the original consensus miR-140-3p or the isomiR with the same seed, miR-140-3p.2.

ORGANISM(S): Homo sapiens

PROVIDER: GSE144367 | GEO | 2020/07/17

REPOSITORIES: GEO

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Project description:miRNAs are small noncoding RNA molecules that play an important role in post-transcriptional regulation of gene expression. Length and/or sequence variants of the same miRNA are termed isomiRs. While most isomiRs are functionally redundant compared to their canonical counterparts, so-called 5âisomiRs exhibit a shifted 5â end and therefore a shifted seed sequence resulting in a different target spectrum. However, not much is known about the functional relevance of these isoforms. Analysis of miRNA-seq data from breast cancer cell lines identified six pairs of highly expressed miRNAs and associated 5âisomiRs. Among them, hsa-miR-140-3p was of particular interest because its 5âisomiR showed higher expression compared to the canonical miRNA annotated in miRbase. This miRNA has previously been shown to control stemness of breast cancer cells. MiRNAseq data of breast cancer patients (TCGA dataset) showed that both the canonical hsa-miR-140-3p and its 5âisomiR-140-3p were highly expressed in patients compared to normal breast tissue. In the current work, we present the functional characterization of 5âisomiR-140-3p and the cellular phenotypes associated with its overexpression in MCF10A and MDA-MB-231 cell lines in comparison to the canonical hsa-miR-140-3p. Contrary to the effect of the canonical hsa miR 140-3p, overexpression of the 5âisomiR-140-3p led to a decrease in cell viability. The latter observation was supported by cell cycle analysis, where the 5âisomiR-140-3p but not the hsa-miR-140-3p caused cell cycle arrest in G0/G1-phase. Additionally, 5âismoiR-140-3p overexpression was found to cause a decrease in cell migration in MCF10A cells. We identified three novel direct target genes of the 5â isomiR-140-3p; COL4A1, ITGA6 and MARCKSL1. Finally, we have shown that knocking down these genes partially phenocopied the effects of the 5âisomiR-140-4p overexpression, where COL4A1 and ITGA6 knockdown led to reduced cell viability and cell cycle arrest, while MARCKSL1 knockdown resulted in a decrease in the migratory potential of cells. In summary, this work presents evidence that there is a functional synergy between the canonical hsa-miR-140-3p and the newly identified 5âisomiR-140-3p in suppressing growth and progression of breast cancer by simultaneously targeting genes related to differentiation, proliferation, and migration. With this array, we aimed to address the question which genes are regulated by either of the two forms of the miRNA. Samples were measured in one biological replicate of cells transfected with mimic-ctrl1 and mimic-ctrl2 (Dharmacon) as control samples and two biological replicates of cells transfected with hsa-miR-140-3p and 5'isomiR-140-3p (Exiqon) in 30nM concentration using Lipofectamin 2000 as transfection reagent.

Project description:miRNAs are small noncoding RNA molecules that play an important role in post-transcriptional regulation of gene expression. Length and/or sequence variants of the same miRNA are termed isomiRs. While most isomiRs are functionally redundant compared to their canonical counterparts, so-called 5’isomiRs exhibit a shifted 5’ end and therefore a shifted seed sequence resulting in a different target spectrum. However, not much is known about the functional relevance of these isoforms. Analysis of miRNA-seq data from breast cancer cell lines identified six pairs of highly expressed miRNAs and associated 5’isomiRs. Among them, hsa-miR-140-3p was of particular interest because its 5’isomiR showed higher expression compared to the canonical miRNA annotated in miRbase. This miRNA has previously been shown to control stemness of breast cancer cells. MiRNAseq data of breast cancer patients (TCGA dataset) showed that both the canonical hsa-miR-140-3p and its 5’isomiR-140-3p were highly expressed in patients compared to normal breast tissue. In the current work, we present the functional characterization of 5’isomiR-140-3p and the cellular phenotypes associated with its overexpression in MCF10A and MDA-MB-231 cell lines in comparison to the canonical hsa-miR-140-3p. Contrary to the effect of the canonical hsa miR 140-3p, overexpression of the 5’isomiR-140-3p led to a decrease in cell viability. The latter observation was supported by cell cycle analysis, where the 5’isomiR-140-3p but not the hsa-miR-140-3p caused cell cycle arrest in G0/G1-phase. Additionally, 5’ismoiR-140-3p overexpression was found to cause a decrease in cell migration in MCF10A cells. We identified three novel direct target genes of the 5’ isomiR-140-3p; COL4A1, ITGA6 and MARCKSL1. Finally, we have shown that knocking down these genes partially phenocopied the effects of the 5’isomiR-140-4p overexpression, where COL4A1 and ITGA6 knockdown led to reduced cell viability and cell cycle arrest, while MARCKSL1 knockdown resulted in a decrease in the migratory potential of cells. In summary, this work presents evidence that there is a functional synergy between the canonical hsa-miR-140-3p and the newly identified 5’isomiR-140-3p in suppressing growth and progression of breast cancer by simultaneously targeting genes related to differentiation, proliferation, and migration. With this array, we aimed to address the question which genes are regulated by either of the two forms of the miRNA.

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MicroRNA-seq of cartilage reveals an over-abundance of miR-140-3p which contains functional isomiRs (Illumina HT12v4 expression arrays)

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