Characterization of microRNA expression in B cells derived from Japanese black cattle naturally infected with bovine leukemia virus by deep sequencing

Abstract

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis (EBL), a malignant B cell lymphoma. However, the mechanisms of BLV-associated lymphomagenesis remain poorly understood. Here, after deep sequencing, we performed comparative analyses of B cell microRNAs (miRNAs) in cattle infected with BLV and those without BLV. In BLV-infected cattle, BLV-derived miRNAs (blv-miRNAs) accounted for 38% of all miRNAs in B cells. Four of these blv-miRNAs (blv-miR-B1-5p, blv-miR-B2-5p, blv-miR-B4-3p, and blv-miR-B5-5p) had highly significant positive correlations with BLV proviral load (PVL). The read counts of 90 host-derived miRNAs (bta-miRNAs) were significantly down-regulated in BLV-infected cattle compared to those in uninfected cattle. Only bta-miR-375 had a positive correlation with PVL in BLV-infected cattle and was highly expressed in the B cell lymphoma tissue of EBL cattle. There were a few bta-miRNAs that correlated with BLV tax/rex gene expression; however, BLV AS1 expression had a significant negative correlation with many of the down-regulated bta-miRNAs that are important for tumor development and/or tumor suppression. These results suggest that BLV promotes lymphomagenesis via AS1 and blv-miRNAs, rather than tax/rex, by down-regulating the expression of bta-miRNAs that have a tumor-suppressing function, and this downregulation is linked to increased PVL.

Bovine leukemia virus encoded blv-miR-b4-3p microRNA is associated with reduced expression of anti-oncogenic gene in vivo

“…However, in our study we did not find any association between blv-miR-b4-3p expression in cattle naturally infected with BLV and HBP-1 mRNA expression levels, compared to the control group (BLV-). In agreement with our observation, Ochiai et al [6] reported that HBP-1 mRNA in B-cells derived from BLV-infected cattle did not differ from those of BLV-negative animals. In a different study, Rosewick and colleagues used an ovine model of BLV infection to describe the expression of BLV-encoded miRNAs in vivo [5].…”

“…In agreement with our observation, Ochiai et al . [ 6 ] reported that HBP-1 mRNA in B-cells derived from BLV-infected cattle did not differ from those of BLV-negative animals. In a different study, Rosewick and colleagues used an ovine model of BLV infection to describe the expression of BLV-encoded miRNAs in vivo [ 5 ].…”

“…Although the production of viral proteins is abolished during the chronic stage, viral transcription is not completely shut down. Different groups have shown that BLV genome encodes for different micro-RNAs (miRNAs) which have the potential to regulate different host metabolic routes and modulate pathogenesis [4][5][6][7][8][9]. miRNAs are small (19-24 bases) non-coding RNAs with posttranscriptional regulatory capacity [10].…”

Diagnosis and Early Prediction of Lymphoma Using High-Throughput Clonality Analysis of Bovine Leukemia Virus-Infected Cells

“…Each DNA sample was tested in duplicate. For the blood and tumor samples of sheep, the BLV tax gene was measured in the DNA samples using real-time PCR, as described previously ( 26 ).…”

Diagnosis and early prediction of lymphoma using high-throughput clonality analysis of bovine leukemia virus-infected cells

“…Each DNA sample was tested in duplicate. For the blood and tumor samples of sheep, the BLV tax gene was measured in the DNA samples using real-time PCR, as described previously (19).…”