| Summary: | Natterins are a recently discovered gene family from the venom gland of Thalassophryne nattereri. Natterin proteins contain a lectin-like domain and a pore-forming toxin-like domain and can cause edema and pain due to their kiniogenase activity. Several natterin-like genes have been found in non-toxic fish species and this indicates other functions of natterin in fish than toxicity. Recently, natterin was found in Arctic charr during a transcriptome study on the different morphs from Lake Thingvallavatn (South Iceland). This species is highly polymorphic and in Lake Thingvallavatn four phenotypic morphs have evolved (small benthic (SB), large benthic (LB), Murta (limnetic, M) and piscivorous limnetic (PI) morph). The transcriptome data revealed that natterin is differentially expressed between the different charr morphs and this lead us to investigate its role in charr in more detail. Charr was found to have at least three natterin paralogues and primers binding the conserved region (general natterin) as well as the different paralogues were designed to examine natterin expressions using quantitative real-time PCR(qPCR). We found that natterin (both general and paralogues) was expressed during embryonic development and the expression was significantly different between morphs (highest in SB) and timepoints (highest in early stages). While general natterin was highest expressed in SB at the early timepoints, the expression of paralogues 1 and 3 was constitutive and the expression of paralogue 2 increased in the later stages in SB. In adult fish tissues the expression of general natterin was highest in the gills whereas natterin paralogue 1 was highest expressed in the kidney and paralogues 2 & 3 in the skin. Natterin paralogue 2 showed the highest expression level during development and in adult fish compared to the other paralogues. However, the observed expression differences of general natterin could not be explained by the differentially expressed paralogues, suggesting the presence of other natterin ...
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