Lineage/species-specific expansion of the Mx gene family in teleosts: Differential expression and modulation of nine Mx genes in rainbow trout Oncorhynchus mykiss

Abstract

Myxovirus resistance (Mx) proteins are interferon (IFN)-inducible Dynamin-like GTPases, which play an important role in antiviral immunity. Three Mx genes (Mx1-3) have been cloned previously in rainbow trout. In this study, an additional six Mx genes were cloned that reside in four chromosomal loci. Further bioinformatics analysis suggests the presence of three teleost Mx groups (TMG) each with a characteristic gene organisation. Salmonid Mx belong to TMG1 and TMG2. The increased salmonid Mx gene copies are due mainly to local gene duplications that happened before and after salmonid speciation, in a lineage/species specific manner. Trout Mx molecules have been diversified in the loop 1 and 4 regions, and in the nuclear localisation signal in loop 4. The trout Mx genes were shown to be differentially expressed in tissues, with high levels of expression of TMG1 (Mx1-4) in blood and TMG2 (Mx5-9) in intestine. The expression of the majority of the trout Mx genes was induced by poly IC in vitro and in vivo, and increased during development. In addition, induction by antiviral (IFN) and proinflammatory cytokines was studied, and showed that type I IFN, IFNγ and IL-1β can induce Mx gene expression in an Mx gene-, cytokine-and cell line-dependent manner. These results show that salmonids possess a large number Mx genes as well as complex regulatory pathways, which may contribute to their success in an anadromous life style.

Expansion of fish CCL20_like chemokines by genome and local gene duplication: Characterisation and expression analysis of 10 CCL20_like chemokines in rainbow trout (Oncorhynchus mykiss)

“…show cytokine-specific effects in terms of modulation of gene expression, as seen previously (Wang et al, 2019b) and in this study. With regards to LPS contamination, the cytokines have been tested for their ability to upregulate known LPS-inducible genes in RTS-11 cells ( Fig.…”

“…Type I IFNa, but not type II IFNγ, was found to be another inducer of CCL20_L expression in RTS-11 cells. As both IL-1β and IFNa are induced by Poly I:C and LPS in rainbow trout (Wang et al, 2019b), the Poly I:C and bacterial infection induced CCL20_L gene expression may be mediated by these proinflammatory cytokines.…”

“…The rainbow trout was stimulated in vivo by the viral dsRNA mimic polyinosinic:polycytidylic acid (Poly I:C, Sigma) as described previously (Wang et al, 2019b). Briefly, 12 fish (~100 g) were injected intraperitoneally (ip) with 1 mg Poly I:C in 0.2 ml PBS and another group of 12 fish were given the same amount of PBS as control.…”

“…The rainbow trout monocyte/macrophage cell line RTS-11 (Ganassin and Bols, 1998) (Hong et al, 2001), IL-6 (100 ng/ml) (Costa et al, 2011) or TNFα (50 ng/ml) (Hong et al, 2013) were added to the cells. All the cytokines were produced in E. coli, purified under denaturing conditions with stringent washing buffer to remove LPS contamination, refolded and re-purified under native conditions, and have been used recently (Wang et al, 2019b). For all treatments, medium alone was added as the control.…”

Selective Stimulation of Duplicated Atlantic Salmon MHC Pathway Genes by Interferon-Gamma

“…This is in line with results from a previous study ( 45 ), where ssMX8 also was strongest regulated by rIFNG stimulation as opposed to MX1-3 genes that displayed a stronger response to type I IFN. Also two rainbow trout sequences clustering with this ssMX8 sequence (onmy-MX5 and onmy-MX6, Supplementary File 6 ), are more stimulated by IFNg than IFNa ( Supplementary File 6 ) ( 46 ).…”