Sequence and expression analysis of rainbow trout CXCR2, CXCR3a and CXCR3b aids interpretation of lineage-specific conversion, loss and expansion of these receptors during vertebrate evolution.
Xu, Qiaoqing a,b; Li, Ronggai a; Monte, Milena M. a; Jiang, Yousheng a,c; Nie, Pin d; Holland, Jason W. a; Secombes, Chris J. a,*; Wang, Tiehui a,*
[Article] Developmental and Comparative Immunology. 45(2):201-213, August 2014.

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Highlights:

* The cDNA sequences of CXCR2, CXCR3a and CXCR3b have been cloned in rainbow trout.

* The linked CXCR1/CXCR2 and CXCR3a/CXCR3b loci are hypothesised to have been present in the teleostomian ancestor.

* CXCR1 and CXCR2 have likely undergone gene conversion whilst CXCR3b has been lost in mammals.

* Compared with mammals, ray-finned fish possess more CXCR1-R3 receptors, but fewer ligands.

* Trout CXCR1-R3 are expressed in macrophages and neutrophils, with CXCR1/R2 also abundant in B-cells.

The chemokine receptors CXCR1-3 bind to 11 chemokines (CXCL1-11) that are clustered on the same chromosome in mammals but are largely missing in ray-finned fish. A second CXCR1/2, and a CXCR3a and CXCR3b gene have been cloned in rainbow trout. Analysis of CXCR1-R3 genes in lobe-finned fish, ray-finned fish and tetrapod genomes revealed that the teleostomian ancestor likely possessed loci containing both CXCR1 and CXCR2, and CXCR3a and CXCR3b. Based on this synteny analysis the first trout CXCR1/2 gene was renamed CXCR1, and the new gene CXCR2. The CXCR1/R2 locus was shown to have further expanded in ray-finned fish. In relation to CXCR3, mammals appear to have lost CXCR3b and birds both CXCR3a and CXCR3b during evolution. Trout CXCR1-R3 have distinct tissue expression patterns and are differentially modulated by PAMPs, proinflammatory cytokines and infections. They are highly expressed in macrophages and neutrophils, with CXCR1 and CXCR2 also expressed in B-cells.

(C) 2014Elsevier, Inc.