MicroRNAs (miRNAs) are endogenous small non-coding RNAs that participate in diverse biological processes via regulating expressions of target genes at post-transcriptional level. Amphioxus, a modern survivor of an ancient chordate lineage, is a model organism for comparative genomics study. However, miRNAs involved in regulating immune responses in Branchiostoma belcheri are largely unclear. In a recent study, researchers from Nanjing Normal University systematically investigated the microRNAs (miRNAs) involved in regulating immune responses in the cephalochordate amphioxus (Branchiostoma belcheri) through small RNA sequencing of amphioxus samples infected with Vibrio parahemolyticus.

Researchers identified 198 novel amphioxus miRNAs, consisting of 12 conserved miRNAs, 33 candidate star miRNAs and 153 potential amphioxus-specific-miRNAs. Using microarray profiling, 14 miRNAs were differentially expressed post infection, suggesting they are immune-related miRNAs. Eight miRNAs (bbe-miR-92a-3p, bbe-miR-92c-3p, bbe-miR-210-5p, bbe-miR-22-3p, bbe-miR-1∼bbe-miR-133 and bbe-miR-217∼bbe-miR-216 clusters) were significantly increased at 12 h post-infection, while bbe-miR-2072-5p was downregulated at 6 h and 24 h. Three miRNAs, bbe-miR-1-3p, bbe-miR-22-3p and bbe-miR-92a-3p, were confirmed to be involved in immune responses to infection by qRT-PCR.

These findings further clarify important regulatory roles of miRNAs in the innate immune response to bacterial infection in amphioxus.

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Reference
P. Jin, L. Sun, C. Lv, F. Ma (2017) Transcriptome-wide analysis of microRNAs in Branchiostoma belcheri upon Vibrio parahemolyticus infection Dev. & Comp. Immuno. doi: 10.1016/j.dci.2017.05.002 [abstract]

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