Molecular characterization and expression analysis of the CCR9 gene from cobia (Rachycentron canadum) following bacterial and poly I:C challenge

Abstract

Chemokine receptors play an important role in coordination of cell trafficking in many biological processes. In this study, a CC chemokine receptor 9 of cobia Rachycentron canadum (RcCCR9) was identified. Analysis of the ORF (1119 bp) of RcCCR9 revealed a predicted protein of 41.87 kDa with typical seven transmembrane domain architecture. RcCCR9 shared several conserved structural features with homologs from mammals and other fish, and had a consistent relationship with phylogenetic trees and sequence identities. Reverse transcription quantitative PCR analysis showed ubiquitous RcCCR9 transcripts in healthy cobia, mainly in immune-related organs, with the highest levels in blood and lower levels in intestines and brain. After challenge with inactivated Vibrio harveyi or viral mimic poly I:C, RcCCR9 expression was up-regulated in head kidney and down-regulated in spleen. Compared with poly I:C, V. harveyi induced a stronger up/down-regulation of CCR9 mRNA levels in the central immune organs. RcCCR9 seems to be strongly involved in host defense against bacterial infection. ARTICLE HISTORY

GPR15–C10ORF99 functional pairing initiates colonic Treg homing in amniotes

“…Treg cells play central roles in maintaining intestinal homeostasis by restraining inappropriate immune responses in the gastrointestinal tract under healthy and pathological conditions (Campbell, 2015 ). The CCR9/CCL25‐chemokine axis controls Treg homing to the small intestine (Perrigoue et al , 2014 ), and CCR9–CCL25 pairing maintains sequence conservation and functional conservation in vertebrates (Devries et al , 2006 ; Galindo‐Villegas et al , 2013 ; Su et al , 2019 ), which is also consistent with the conservation of the small intestine in vertebrates (Devries et al , 2006 ; Bird & Tafalla, 2015 ). Notably, the gastrointestinal tracts of zebrafish and medaka express colon‐specific genes (Wang et al , 2010 ; Aghaallaei et al , 2016 ).…”

A novel chemerin receptor 1 (Chemerin1) takes part in the immune response of cobia (Rachycentron canadum)

“…Chemerin 1 is regulated by several cytokines and pathogen-associated molecular patterns (PAMPs), and its activation leads to up-regulation of the phosphatidylinositol 3-kinase/Akt signaling pathway and down-regulation of NF-κB [9] , [10] . Previous studies demonstrated that expression levels of some pro-inflammatory cytokines, e.g., IL-1β, IL-8, TNF-α , and chemokine CC ( CCR3 ) [36] , [37] , and chemokine receptor, CCR9 [38] , [39] , were up-regulated in immune organs of cobia following bacterial or poly I: C challenge. V. harveyi is a gram-negative, rod-shaped, facultatively anaerobic, and non-spore forming bacterial species, which can infect cobia and other fish species [34] , and poly I: C is a synthetic double-stranded RNA (dsRNA), which can mimic the viral infection [35] .…”