Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2012
Publication Date: May 26, 2012
Repository URL: http://hdl.handle.net/10113/55799
Citation: Shepherd, B.S., Rees, C.B., Binkowski, F., Goetz, F. 2012. Characterization and evaluation of sex-specific expression of suppressors of cytokine signaling (SOCS) -1 and -3 in juvenile yellow perch (Perca flavescens) treated with lipopolysaccharide. Fish and Shellfish Immunology. 33:468-481. Interpretive Summary: Yellow perch are highly prized as a recreational and food fish. The strong demand for yellow perch in the Midwest traditionally has been met by a commercial wild-capture fishery. Recent declines in wild stocks of the Great Lakes region of the U.S. and Canada, and restrictions on capture fisheries, have fueled the need for aquaculture production as a means to meet increasing demand for yellow perch. However, expansion of yellow perch aquaculture has been limited by the slow growth of this species in aquaculture settings. Additionally, growth in yellow perch is sexually-dimorphic wherein females grow larger and faster than males; such size discrepancies pose further difficulties with production of this species. Consequently, effort has been devoted to understanding the basis of sex-specific differences in growth and development in yellow perch. We have previously shown that estrogen promotes growth and also influences genes involved with immune function, growth and metabolism in this species. More recently, we found that spleen size is greater in females than in males. Interestingly, work in rainbow trout has shown that larger spleen size confers better immunity to pathogens. Given these sex-specific differences in yellow perch physiology and morphology, and the need to better understand the differences in the biochemical pathways that affect growth and immune function in yellow perch, we took the initial step to characterize the nature and function of key biomolecules involved with the immune and growth responses, specifically suppressors of cytokine signaling (SOCS). Our findings suggest the involvement of the suppressor of cytokine signaling (SOCS) genes in the yellow perch immune response and that differences among the sexes are evident and should be explored further. This information will be helpful in formulating future research to improve immune function in commercially-important finfish.
Technical Abstract: The suppressor of cytokine signaling (SOCS) proteins are a family of intracellular proteins that are centrally involved with vertebrate growth, development and immunity via their effects as negative feed-back regulators of cytokine (and hormone) signaling. The genes for SOCS-1 & -3 were cloned, sequences analyzed and expression patterns examined in the commercially-important teleost, yellow perch (Perca flavescens). The deduced (mature) proteins for yellow perch (yp)SOCS-1 and (yp)SOCS-3 consist of 211 and 205 amino acids, respectively. Functional domains such as the Src homology-2 (SH2) and SOCS-box were present in ypSOCS-1 and ypSOCS-3 and these domains were well conserved between teleost species. Sequence analysis showed that ypSOCS-1 & -3 share highest homology (among similar teleost sequences) to the stickleback (Gasterosteus aculatus) SOCS-1 & -3 protein homologues. To investigate sex-specific expression of the ypSOCS-1 and ypSOCS-3 mRNAs, juvenile male and female yellow perch were immunologically challenged with a single injection (10 micro grams/gram bw) of lipopolysaccharide (LPS) and tissues (gill, head kidney, kidney, liver and spleen) were sampled over a 48-hour time-course. Quantitative real-time PCR analysis showed that ypSOCS-1 & -3 were expressed in all tissues examined and at all sampling time-points. LPS injection significantly induced ypSOCS-1 & -3 mRNA levels in gill, head kidney, liver, kidney and spleen, with maximal induction occurring at 6 hours post-injection in each tissue. By 48-hours post-injection, expression levels for ypSOCS-1 & -3 mRNAs approached, or reached, control levels in all tissues examined. While there were statistical interactions among variables (treatment, time and sex) for ypSOCS-1, we only found a main effect of sex on SOCS-3 mRNA expression in head kidney with higher copy numbers occurring in males than in females treated with LPS. Sexually-dimorphic expression of SOCS-1 or -3 mRNA has not been examined, or described, in a teleost. Our findings suggest the involvement of the SOCS genes in the yellow perch immune response and that differences among the sexes are evident and should be explored further.