Two Macrophage Colony-Stimulating Factor Genes Exist in Fish That Differ in Gene Organization and Are Differentially Expressed

Abstract

Mammalian macrophage CSF (MCSF; CSF-1) is the primary regulator of the mononuclear phagocyte lineage. We, for the first time, report the complete sequencing of five MCSF cDNAs from three fish species, rainbow trout, zebrafish, and goldfish. Despite the difference in the lengths of the MCSF transcripts, all of the fish MCSF molecules encode a signal peptide, a CSF-1 domain, a transmembrane domain, and an intracellular region. Each fish MCSF gene has a unique exon/intron structure. The primordial MCSF gene may have had a nine exon/eight intron structure. In this model, insertion of an intron in exon 6 in primitive fish created the fish type I MCSF, while the loss of this exon or part of the original exon 6 created the fish type II MCSF. Investigation of alternative splicing variants in trout suggests that no mammalian equivalent splice variants exist. The two trout MCSF genes are differentially expressed in vivo and contributed differently to the high-level expression of MCSF in spleen and head kidney. In contrast to the up-regulation of MCSF by PMA in mammals, in trout MCSF1 expression is down-regulated by PMA treatment. As in mammals, recombinant trout MCSF1 can promote the growth of head kidney leukocytes, and it up-regulates the expression of CXCR3 in head kidney macrophages, with the latter suggesting a role of MCSF in the trafficking of macrophages to sites of inflammation or injury where the CXCR3 ligands are expressed. Thus MCSF has an important role in the immune system of fish as in mammals.

Phylogenetic analysis of vertebrate CXC chemokines reveals novel lineage specific groups in teleost fish

“…In addition to cells expressing the CD4 molecule, macrophages could also be targeted by CXCL11_L1, CXCL_F4 and CXCL_F5 since elevated transcript levels of MCSFR were seen in the migrated cell fraction. In fish, a putative receptor (CXCR3) for CXCL11_L1 has recently been identified and shown to be expressed in mononuclear phagocytes and macrophages (Aghaallaei et al, 2010;Wang et al, 2008). However, direct interaction between putative fish CXCR3 and CXCL11_L1 has yet to be determined.…”

Functional Characterization of a Nonmammalian IL-21: Rainbow Trout Oncorhynchus mykiss IL-21 Upregulates the Expression of the Th Cell Signature Cytokines IFN-γ, IL-10, and IL-22

“…RNA preparation, cDNA synthesis, and real-time PCR analysis of gene expression were as described previously (42,43). Six healthy rainbow trout (average weight, 120 g) were killed, and eight tissues (gills, skin, muscle, liver, spleen, HK, intestine, and brain) were collected.…”

“…ml), dexamethasone (DM, 0.5 mg/ml), or PHA (from red kidney bean Phaseolus vulgaris; 10 mg/ml) for 4, 8, and 24 h. All the chemicals were from Sigma-Aldrich, and the stimulants were diluted in complete medium just before addition to the cells. The concentrations chosen for each stimulant were deemed optimal from previous studies (43)(44)(45)(46). The treatments were terminated by dissolving the cells in TRIzol (Invitrogen).…”

DNA vaccination against a fish rhabdovirus promotes an early chemokine-related recruitment of B cells to the muscle

“…Although at this early stage, there is still a considerable infiltration of leukocytes as a result of tissue damage, it might be interesting in the future to study whether CXCL11 L1 is also capable of recruiting B cells as reported in some mammalian species [46], despite the fact that previous evidence in trout suggests that CXCL11 L1 is mainly chemoattractant for macrophages and CD4 + cells [36]. CXCL10 is a gamma interferon inducible CXC chemokine, as is CXCL9 and CXCL11, all of them sharing the same receptor, CXCR3, which in trout has two different isoforms [47]. Interestingly, we have observed a significant up-regulation of CXCR3B in vaccinated animals that suggests that this chemokine-chemokine receptor association is maintained in teleost.…”