An invertebrate-specific miRNA targeted the ancient cholinergic neuroendocrine system of oyster

• Main Authors: Hao Chen, Zhi Zhou, Lingling Wang, Hao Wang, Rui Liu, Huan Zhang, Linsheng Song
• Format: Article
• Language: English
• Published: The Royal Society 2016-01-01
• Series: Open Biology
• Subjects: mirna; mir-2 family; choline transporter-like protein; acetylcholine; cholinergic system; immunomodulation
• Online Access: https://royalsocietypublishing.org/doi/pdf/10.1098/rsob.160059

Acetylcholine (ACh) is the main neurotransmitter in the cholinergic neuroendocrine system and plays an indispensable role in modulating diverse immune responses. As important transporters in choline uptake, choline transporter-like proteins (CTLs) can control ACh synthesis and release indirectly in multiple organisms. In this study, cgi-miR-2d, an invertebrate-specific miRNA in oyster Crassostrea gigas, is proved to repress the synthesis/release of ACh by targeting CgCTL1 and choline uptake in haemocytes during the early stage of pathogen infection. In short, an opposite expression pattern between CgCTL1 and cgi-miR-2d is observed during Vibrio splendidus infection, accompanied by changes in haemolymph ACh. In addition, the expression level of CgCTL1 is found to be significantly repressed after cgi-miR-2d overexpression in vivo, while both haemocyte choline and haemolymph ACh are also decreased simultaneously, similar to the finding in CgCTL1 knock-down assay. As a result, the expression of two tumour necrosis factor-like proteins and the bacteriostatic activity of oyster haemocytes are found to be altered significantly by either gain-of-function cgi-miR-2d or knock-down of CgCTL1. To our knowledge, this is the first miRNA identified in invertebrates that can target the ancient cholinergic system and augment immune response during infection.